Equine Surgery || Adnexal Surgery

Adnexa of the eye include the eyelids and conjunctiva, nictitat-ing membrane, and nasolacrimal system. Each of these adnexa contributes to health of the eye by maintaining a normal physi-ologic environment. Disorders of each of these adnexa can have deleterious effects on health of the globe and vision, and so each is addressed separately in this chapter.

EYELIDSAnatomy and PhysiologyThe different eyelid functions include protection of the globe, optimization of light transmission and refraction through the cornea, maintenance of globe position within the orbit, and musculature and motor control. These functions are discussed in detail later.

Protection of the Globe

The upper eyelid cilia (eyelashes; Figure 56-1) provide protec-tion from light and foreign material. Reflex blinking is initiated by tactile sensation from the cornea, eyelid skin, cilia, or tactile hairs (vibrissae; see Figure 56-1, A and B). Blinking completely closes the palpebral fissure except at the medial canthus where the caruncle protrudes. The glandular secretions of the eyelids

include those from the cilia-associated glands of Zeis (seba-ceous) and Moll (apocrine), and the tarsal or meibomian glands (the meibomian gland orifices are visible clinically as the “gray line;” see Figure 56-1, D). These secretions provide components to the preocular tear film that is important for protecting the eye.

Optimization of Light Transmission and Refraction through the Cornea

The eyelids maintain optical clarity by distributing tears uni-formly across the ocular surface. Loss of blinking immediately impairs corneal clarity. The physical action of blinking pumps tears down the nasolacrimal duct via the upper and lower lac-rimal punctae (see Figure 56-1, C), promoting a uniform pre-ocular tear film.1

Maintenance of Globe Position within the Orbit

The fibrous tissues and periocular muscles aid in globe retrac-tion in combination with the extraocular muscles.

The eyelids consist mainly of skin, striated muscle, fibrous supportive tissue, and conjunctiva (Figure 56-2). The skin is thin and is covered with fine dermal hair, which is absent

CHAPTER

56 Adnexal SurgeryFreya Mowat and Joshua T. Bartoe

Figure 56-1. Overview of anatomy of the equine ocular adnexa. A, Equine eye, lateral view. Cilia (eyelashes) are present in the lateral two thirds of the upper eyelid. Lower eyelid cilia are poorly developed.92 Upper and lower eyelid skin contains tactile vibrissae (white arrows). The palpebral fis-sures meet at the medial and lateral canthi, and the leading edge of the nictitating membrane is visible at the medial canthus. B, Equine eye, ante-rior view. White arrows delineate the position of the tactile vibrissae. C, Cannulation of the upper and lower nasolacrimal puncta to highlight their location. White arrows identify the puncta. D, Magnified view of the upper eyelid mucocuta-neous junction. Arrows delineate the openings of the meibomian gland orifices (the gray line). LC, Lateral canthus; MC, medial canthus; NM, nictitat-ing membrane.

Cilia

NMMC

LC

A

C

B

D

744

CHAPTER 56 ADnExAL SuRgERy 745

Figure 56-2. Cross-sectional anatomy of the normal upper eyelid.

Orbital fat

Orbital septum

Orbicularisoculi muscle

Levator palpebraesuperioris muscle

Müller's muscle

Sweat gland

Tarsal plate

Gland of Moll

Gland of Zeis

Cilia

Meibomian gland

Palpebral conjunctiva

Bulbar conjunctiva

Conjunctivafornix

Musculature and Motor Control

The eyelids are maintained in a roughly elliptical shape by the presence of the lateral and medial palpebral ligaments that restrict movement at the lateral and medial canthi (Figure 56-3). The ligaments originate at the bony orbital rim and insert on the orbicularis oculi muscle. The medial palpebral ligament is a defined fibrous band that overlies the lacrimal sac; the lateral ligament is a wider band containing muscle fibers.3 The eyelids close in a lateral to medial direction by the contraction of the encircling orbicularis oculi muscle, (see Figure 56-3).2,3 Opening the eyelids requires the combined action of multiple muscles that insert onto and antagonize the action of the orbicularis oculi muscle. The upper eyelid is larger and more mobile than the lower, and it has greater muscular control. The levator anguli oculi medialis (or corrugator supercilii) muscle inserts a third of the way from the medial canthus and contributes to the asymmetric ellipse of the eyelid aperture.2 This asymmetry is enhanced during excitement by contraction of the levator pal-pebrae superioris muscle and levator anguli oculi medialis muscle of the upper lid and the malaris muscle of the lower lid (see Figure 56-3). Müller’s muscle in the upper eyelid (in close association with the levator palpebrae superioris muscle) con-tains smooth muscle innervated by the sympathetic nervous system. The facial nerve (cranial nerve [Cn] VII), via the auricu-lopalpebral and dorsal buccal branches, provides the majority of motor innervation to the eyelid musculature. Exceptions include the levator palpebrae superioris, which is innervated by the oculomotor nerve (Cn III), and Müller’s muscle, innervated by the sympathetic nervous system.

Sensory Innervation

The trigeminal nerve (Cn V) provides sensory innervation to the eyelid skin. The upper eyelid and canthi are innervated by three branches of the ophthalmic division of Cn V.4 The supra-orbital nerve (a branch of the frontal nerve) emerges from the palpable supraorbital foramen in the zygomatic process of the frontal bone. The lacrimal nerve emerges at the dorsolateral aspect of the orbital rim. The infratrochlear nerve emerges at a notch in the dorsomedial part of the orbital rim. This nerve also serves the lacrimal caruncle, third eyelid, nasolacrimal puncta, and ducts and areas of the conjunctiva.3 The lower eyelid is

Figure 56-3. Muscles and motor innervation of the equine eyelids.

Levator anguli oculi medialis muscle(palpebral branch of CN VII)

Medial palpebralligament

Malaris muscle(dorsal buccal branch of CN VII)

Orbicularis oculi muscle(palpebral branch of CN VII)

Lateral palpebral ligament(palpebral branch of CN VII)

Levator palpebrae superioris muscle(dorsal branch of CN III) plusMüller's muscle (sympathetic)

Frontalis muscle(palpebral branch of CN VII)

adjacent to the eyelid margin. Sebaceous and apocrine glands are present within the skin. There is sparse subcutaneous loose connective tissue between the skin and the eyelid muscles, and this tissue does not contain any fat.2 Connective tissue sur-rounds the muscles of the eyelid and blends with the fascial sheaths and orbital septum. Deep to the eyelid musculature is a region of dense connective tissue known as the tarsal plate. The tarsal plate is most pronounced close to the eyelid margins, blends with the fibers of the palpebral ligaments, and provides structural integrity to the eyelids. The tarsal plate is more exten-sive in the upper eyelid than the lower. The meibomian (i.e., tarsal) glands are embedded within the tarsal plate and provide the outer lipid component to the tear film, which is important in the maintenance of tear film stability.

746 SECTION VIII EyE AnD ADnExA

sedation with minimal cardiopulmonary depression.7 Sudden head jerking may occur with the use of opioids in horses, which can be minimized by using them in combination with α2-adrenoreceptor agonists.8 A longer duration of sedation may be achieved using detomidine infusions with a loading dose of 7.5 µg/kg followed by a constant-rate infusion of 0.6 µg/kg/minute (infusion rate halved every 15 minutes), providing seda-tion for up to 135 minutes.9

Topical anesthetic may be applied to the eye to facilitate examination and as an adjunct to minor procedures. Propara-caine hydrochloride 0.5% solution has an onset time of 5 minutes and effect duration of 25 minutes following instillation of 0.2 mL of solution.10 However, even at maximal effect, some corneal sensation remains. Complete corneal anesthesia can be achieved using 0.5% tetracaine ophthalmic preparations (Tetra-Visc, viscous ophthalmic drops, 0.5%) when applied as 2 drops, 1 minute apart.11 It has an onset time of 5 minutes and effect duration of 60 minutes. In addition to instillation into the con-junctival sac, local anesthetic eye drops can be first applied to cotton-tipped applicator swabs and held in apposition to areas where biopsies or surgical manipulation will be performed.

Regional nerve blocks can be used to provide both motor akinesia and sensory analgesia. Lidocaine hydrochloride 1% or 2% without epinephrine (1 to 2 mL per site12) has an onset time of 2 to 5 minutes and effect duration of 1 to 2 hours.13,14 Mepi-vacaine hydrochloride has similar onset time but has slightly longer effect duration of 2 to 3 hours.13,14 Bupivacaine hydro-chloride without epinephrine is available in 0.25% to 0.75% concentrations and has an effect duration up to 10 hours.13,15 After ocular examination, topical lubricants are indicated fol-lowing instillation of local anesthetic drops and motor or sensory nerve blockade, because tear production and distribu-tion will be impaired.

Motor Blockade

The upper eyelid akinesis provided by local blockade of the auricu-lopalpebral nerve facilitates ophthalmic examination and minor adnexal procedures by limiting the palpebral reflex (Figure 56-4). For additional details refer to Chapter 55.

Sensory Blockade

A number of local sensory nerve blocks can be used to anesthe-tize specific regions of the eyelids (see Figure 56-4).5,12,14,16 The central portion of the upper eyelid is anesthetized using the supra-orbital block. The supraorbital foramen is palpable clinically as a small depression within the supraorbital process of the frontal bone. The lateral upper eyelid and lateral canthus are anesthetized using the lacrimal block. A line of local anesthetic is injected along the lateral third of the dorsal orbital rim. The medial canthus is anesthetized using the infratrochlear block. Local anes-thetic is injected through the bony trochlear notch on the dorsal rim of the orbit near the medial canthus.12 The lower eyelid is anesthetized using the zygomatic block. A line of local anesthetic is injected along the ventrolateral orbital rim.

Diagnostic ProceduresRadiography, computed topography (CT), or magnetic reso-nance imaging (MRI) should be considered in cases of eyelid trauma when concurrent orbital fractures or draining tracts are suspected.17 Further details on imaging techniques are provided

innervated by the zygomaticofacial branch of the maxillary divi-sion of Cn V and emerges at the ventral orbital rim.

Vasculature and Lymphatics

The eyelids are well vascularized, which facilitates rapid healing of eyelid injuries. The major arterial supply is derived from the angularis oculi artery (a branch of the facial artery) and enters the region at the medial border of the medial palpebral liga-ment. Accessory arterial supply is provided by the rostral deep temporal artery and branches of the external ophthalmic arter-ies, including the supraorbital and lacrimal arteries and the malar artery.2 The major venous drainage occurs via the infratrochlear vein (upper eyelids) and the reflex vein (lower eyelids and medial canthi), all joining the ophthalmic vein to drain into the internal maxillary vein.3 The eyelids have signifi-cant lymphatic drainage, predominantly to the ipsilateral sub-mandibular and parotid lymph nodes.

Ophthalmic Examination Techniques and FindingsIn the investigation of eyelid abnormalities, a systematic approach to diagnosis should always be adopted, including a full bilateral ophthalmic examination and, where indicated, a systemic physi-cal examination. This is particularly important when assessing trauma cases, because significant intraocular disease may be present, which may affect the choice of treatment. Initially a “hands-off” examination to evaluate comfort (epiphora, evi-dence of self-trauma, blepharospasm, etc.) should be performed. Subtle ocular discomfort or eyelid deformity can be noted by examining the angle of the upper eyelid cilia relative to the surface of the cornea; in an uncomfortable eye with blepharo-spasm, the angle formed between the cilia and the cornea is more acute.5 Any asymmetry of eyelid position, swelling or depressions of eyelid or periorbital tissues and should be noted and exam-ined further as necessary. Ptosis in combination with sweating is a consistent symptom of Horner syndrome in horses; enophthal-mos and third eyelid protrusion may be less-consistent findings.6 Vision, eyelid innervation, and eyelid function should be evalu-ated using the menace response. Both the palpebral and corneal reflexes can be evaluated; it should be noted whether the blink in each test is complete or incomplete. A complete ophthalmic examination should be performed using focal illumination and magnification; a bright light source (Finhoff transilluminator) and magnifying loupes, a direct ophthalmoscope, or a slit lamp biomicroscope are all appropriate choices.

Assuming good general health of the horse, standing seda-tion can assist with restraint for examination and can be an alternative to general anesthesia for minor surgical procedures. The patient is usually placed in restraint stocks, and cross ties or headrests can be used to achieve greater head stability for surgical procedures. Thoracic auscultation is recommended before sedation because of the cardiovascular suppression induced by sedative agents.7 Short-duration sedation can be given via intravenous bolus. The α2-adrenoreceptor agonists detomidine hydrochloride (0.01 to 0.02 mg/kg IV) and xylazine hydrochloride (0.4 to 1.1 mg/kg) each provide analgesia and sedation. Onset of peak activity of xylazine is within 3 to 5 minutes and lasts 30 to 40 minutes at the high end of the dosage range.7 In fractious animals, a combination of detomidine hydrochloride (0.01 to 0.015 mg/kg IV) and the opioid butor-phanol (0.02 to 0.03 mg/kg IV) may provide a deeper plane of


adjunctive therapy has been widely described in the treatment of periocular squamous cell carcinoma and sarcoids, and it can provide a better clinical response than surgery alone. The choice of adjunctive therapy depends on tumor size and location, availability of equipment, financial considerations, and the cli-nician’s expertise. The choice of therapy should be made in conjunction with a histopathologic diagnosis.

Squamous Cell Carcinoma

The eyelid is a common site for development of adnexal squa-mous cell carcinoma (SCC) in horses,24,30,31 and approximately 16% of cases have bilateral lesions.30 The periorbital location carries a poorer prognosis than other locations on the body, and the eyelid location carries a poorer prognosis for recurrence than the nictitating membrane, nasal canthus, or limbal con-junctival locations.30 SCC can spread locally, and a 6% to 10.2% rate of metastasis to local lymph nodes is reported.24,32,33 Metas-tasis to the thorax and salivary glands has also been reported, although the frequency of this has not been indicated.34

Published studies have identified a predilection for draft breeds, Appaloosas, and Paints.32,35-37 Incidence rises in middle-aged to old animals, with the ocular and skin forms occurring at a mean age of 13 years and 15 years, respectively, which is significantly earlier than penile, vulval, and perianal forms.37

in Chapters 67 to 71. When eyelid neoplasia is suspected, fine needle aspiration or surgical biopsy of masses, suspicious ero-sions, and regional lymph nodes should be considered to obtain a cell type diagnosis. Eyelid biopsy specimens are com-monly fixed in 10% formalin (minimum 10 times the volume of the sample) before submission for histopathology. Suspected infectious eyelid diseases can be thoroughly investigated with impression smears or exfoliative cytology specimens and bacte-rial or fungal culture with antibiotic sensitivity assessment.

NeoplasiaThe differential diagnosis for adnexal neoplasia in the horse commonly includes squamous cell carcinoma, sarcoid, and melanoma18,19; less commonly reported connective tissue tumors are fibroma, fibrosarcoma,20-22 and lymphosarcoma.23 Other reported tumor types include adenocarcinoma,22 schwannoma,24 neurofibroma,25 plasmacytoma, mast cell tumor, papilloma,26 and hemangiopericytoma.27 neoplasia should be differentiated from blepharitis induced by bacterial, fungal, or parasitic disease including ocular habronemiasis.28

Infiltrative periorbital neoplasms may require radical exci-sion, potentially necessitating enucleation or exenteration, peri-orbital ostectomy, and skin grafting.29 Although surgical therapy is the principal method of treatment for smaller eyelid masses,

Figure 56-4. An overview of motor and sensory nerve block sites. A, Distribution of the sensory inner-vation of the periocular skin of the horse. B, The sites for sensory nerve blockade (numbers) and upper eyelid akinesia. C, The same sites superimposed onto the equine skull. AP, Auriculopalpebral nerve block: motor, upper eyelid; 1, supraorbital nerve: sensory, central upper eyelid; 2, infratrochlear nerve: sensory, medial canthus; 3, lacrimal nerve (line block): sensory, lateral eyelid; 4, zygomatic nerve (line block): sensory, lower eyelid.

AP

2

1

4

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2

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BA

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AP 3

1

2

4


Sarcoids usually develop in young horses between 3 and 6 years of age.42 Quarterhorses, Appaloosas, Arabians, and Thorough-breds may be at increased risk, and Standardbreds and Lipiz-zaner have a reduced risk.45,46 Bovine papillomavirus infection has been associated with sarcoid development.43,47-49 The prog-nosis for periocular sarcoid should be considered guarded because recurrence despite aggressive therapy is common.5

Summaries of the adjunctive therapy options are outlined in Table 56-3. Surgical debulking has been recommended before many of the adjunctive therapies described. Connective tissue tumors such as fibromas, fibrosarcomas, and neurofibromas should be treated in similar manner to sarcoids, because the success of surgical excision alone is poor.19 For information on sarcoids located in other areas, see Chapter 29.

Anesthetic ConsiderationsIn cases of trauma where eyelid lacerations have occurred, evalu-ation should be made regarding the presence and extent of orbital fractures that in extreme cases may involve the cranial cavity. This may affect the animal’s demeanor and level of aware-ness, the timing of which can lag behind the initial injury.50 Therefore sedation should be used with caution in cases where severe head trauma is suspected (to avoid iatrogenic cerebral edema). Trauma could also involve paranasal sinuses, and in these cases, airway inflammation, hemorrhage, or both could increase the potential for anesthetic complications. Anesthetic recovery should be as smooth as possible, and padded helmets can protect surgical sites during recovery.51

Required Surgical EquipmentStandard equipment useful for eyelid surgery is outlined in Table 56-4 and shown in Figure 56-6. Ophthalmic instruments should be kept in a protective container with plastic or foam compartments to protect the fine tips of these instruments. Instruments should be cleaned carefully using fine brushes.

Recommended suture materials are listed in the later descrip-tions of individual procedures. Most eyelid procedures can be performed using reverse cutting needles, and swaged suture materials minimize tissue drag. Firm monofilament sutures such as nylon should be used with caution close to the cornea to prevent abrasions.

Additionally, cellulose sponges (Weck-Cel, Medtronic, Jack-sonville, FL) or cellulose sticks can be used to absorb fluids without damaging the ocular structures. Throughout surgery, regular application of balanced salt solution to the corneal surface is recommended to prevent corneal desiccation. Cautery is often beneficial because the eyelids are highly vascularized. Cryotherapy units used in general surgery can be used for oph-thalmic interventions. Liquid nitrogen, carbon dioxide, or nitrous oxide units can be used. Magnifying loupes with or without a light source are useful, and are available with magni-fications from ×1.5 to ×5. Loupes should have a comfortable working distance between 20 and 30 cm.

Relevant PharmacologyTetanus vaccination status should be established in all cases of trauma, and vaccine or tetanus antitoxin should be adminis-tered where the status is unknown or a booster is overdue. If

Exposure to ultraviolet light is a risk factor for the development of SCC, with greater incidence in sunny locations and higher altitudes.35 Animals with minimal or no periocular pigmenta-tion are at increased risk (Figure 56-5).26,35 Solar-induced epi-thelial hyperplasia and squamous metaplasia often precede the development of carcinoma in situ (where the tumor has not yet invaded through the lamina propria of the epithelium) and overt SCC.38 Tattooing of the equine eyelids and third eyelid to prevent the development of SCC has been described, lasting 2 to 3 years.39 There has been no prospective study in horses to show the extent of protection that tattooing provides against solar radiation damage, although there are reports in humans of SCC forming within tattooed skin.40,41

Recurrence is a concern following surgical excision, and one study determined a recurrence rate of 68.2% with excision alone.31 A large study conservatively estimated a survival time of 47 months for animals affected with adnexal SCC.30 The progno-sis is markedly reduced following one or more recurrences.30 Lesions smaller than 1 cm in diameter and 0.2 cm in depth can be managed successfully using cryotherapy, radio frequency hyperthermia, beta radiation, or laser ablation treatment, whereas lesions with a surface area of 1 to 2 cm and depth greater than 0.2 cm require cryosurgery, laser ablation, interstitial radio-therapy, or serial cisplatin injections.19 Enucleation or exentera-tion should be considered for large, infiltrative lesions. Studies evaluating adjunctive therapies are detailed in Table 56-1. For information of SCC in other areas, please see Chapter 29.

Sarcoids

Although not classified as malignant, sarcoids are common, locally invasive fibroblastic neoplasms that frequently recur fol-lowing therapy. Periocular sarcoids can cause ocular irritation and swelling of the eyelids, impairing function and abrading the cornea.42 A previous study found that 14% of sarcoids occur exclusively in the periocular region, and of these, 78% are uni-lateral and 67% affect the upper eyelid.42 Sarcoids can be divided into five broad categories: occult, verrucose, nodular (types a and b), fibroblastic (types a and b), and mixed.42,43 Specific clinical features may indicate which type of sarcoid is present,44 as outlined in Table 56-2. Biopsy or injury of sarcoids can result in the development of a more-aggressive tumor type.44

Figure 56-5. A squamous cell carcinoma (black arrow) and melanoma (white arrow) affecting the lower palpebrum in a horse with no eyelid pigmentation. (Courtesy Dr. Derek Knottenbelt.)

Text continued on p. 753


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TABLE 56-2. Clinical Characteristics of Different Types of Equine Sarcoids

Type of Sarcoid Predilection Sites Clinical Appearance

Occult Head, neck, hairless skin Circular, alopecic with small cutaneous nodules and/or mild hyperkeratosis

Verrucose Face, axilla, groin Hyperkeratosis, prominent scaling, resemble papillomas or fibropapillomas

nodular type A not described Firm, well-defined subcutaneous spherical nodules, no dermal involvement

nodular type B not described Firm, well-defined subcutaneous spherical nodules, clear dermal involvement

Fibroblastic type 1 (pedunculate)

groin, eyelid, lower limbs, coronet, site of previous skin trauma or other sarcoid

1a: narrow neck with only superficial involvement1b: narrow neck with deep and superficial involvement

Fibroblastic type 2 (sessile) groin, eyelid, lower limbs, coronet, site of previous skin trauma or other sarcoid

Broad, locally invasive base

Mixed (progressive state between verrucose/occult and fibroblastic/nodular)

not described Very variable appearance

Malignant/malevolent Jaw, face, elbows, medial thighs Often follows biopsy or trauma of fibroblastic mass. Invasive, metastasize readily to lymph nodes

Adapted from Knottenbelt DC: A suggested clinical classification for the equine sarcoid. Clin Tech Equine Pract 4:278, 2005; Knottenbelt D, Edwards S, Daniel E: Diag-nosis and treatment of the equine sarcoid. In Pract 17:123, 1995.

TABLE 56-3. Summary of Adjunctive Therapies Published for the Treatment of Periocular Sarcoid

Treatment

Number of Periocular Cases Type of Sarcoid Protocol Outcome Ref.

Surgical excision alone

28 Superficial verrucose, well defined nodular type A

1-2 cm margins 82% local recurrence 42, 103

Cryotherapy 9 not specified −20° C for minimum 2 freeze-thaw cycles, freezing extending beyond margin. Multiple treatments, in some cases liquid nitrogen or nitrous oxide

56% local recurrence 104

2 on head not specified Surgical debulking, 2 freeze-thaw cycles to −25° C, 2- to 3-week intervals for 1-5 cycles, liquid nitrogen

no recurrence at 15 and 16 months

105

23 Small verrucose or occult

Triple freeze-thaw to −25° C using liquid nitrogen unit

91% recurrence within 12 weeks

42

Hyperthermia 2 not specified 64° C daily × 4 sessions. Followed procedure outlined in reference 105 but repeated at 4-day intervals

100% recurrence 42

Topical chemotherapy

9 Superficial occult or verrucose

5% 5-fluorouracil twice daily, tapering every 5 days

67% resolved 42

146 Small superficial verrucose

AW4-LuDES (mixture of 10% 5-fluorouracil and rosemary oil) ointment once daily for 5 days

35% resolved 42

Continued


Treatment


Intralesional chemotherapy

12 not specified Cisplatin 1 mg/cm3 in an oil/water suspension every 2 weeks for 4 treatments

Mean nonrecurrence, 21.6 months; 1 year nonrecurrence of 87%

97

18 Fibroblastic, extensive nodular

Cisplatin 1 mg/cm3 at 5- to 7-day intervals for up to 6 treatments

33% resolved (all nodular)

42

4 not specified Debulking of larger tumors and implantation of 3 mm degradable beads containing 7% cisplatin at 1.5 cm intervals, mean of 2.4 treatments

75% had nonrecurrence for at least 2 years

22

5 on head not specified 5-fluorouracil 50 mg/cm3, 2 to 7 treatments

60% resolved 106

103 not specified Surgical debulking for larger tumors followed by cisplatin 1 mg/cm3 in an oil/water suspension every 2 weeks for 4 treatments

Periocular cases not examined separately; cisplatinalone: 2-year nonrecurrence = 97%, 5-year nonrecurrence = 93.7%; withsurgery: 2-year nonrecurrence = 89% to 100%, 5-year nonrecurrence = 87.5% to 100% (depending on timing of treatment and extent of residual disease); prior cryotherapy negatively affected prognosis

98

Bacille Calmette-guérin vaccine

26 not specified Surgical debulking for large tumors, 1 mL/cm3 of 0.75 mg/mL BCg cell-wall fraction, 1 to 6 treatments

no recurrence in 24 months

107

1 head, 1 eye not specified BCg cell-wall fraction, 3 to 4 treatments

no recurrence in 20 months in eye case, 50% reduction in size in 11 months in head case

105

3 on head not specified Live BCg vaccine, 5 to 6 treatments

no recurrence in 66% cases in 12 and 18 months, respectively; 90% “remission” in 18 months in 1 case

105

7, 3 with histological confirmation

not specified 2 to 7 treatments of intralesional 0.75 mg/mL BCg cell wall fraction 1 to 10 mL

nonrecurrence of 53 to 260 days

108

1 nodular type B 5 treatments of 10 mL intralesional every 2 weeks

no recurrence 2 years 109

309 Occult, verrucose (26)

nodular, fibroblastic, mixed (283)

Intralesional 1 mL/cm2 of tumor surface every 2 to 4 weeks

Verrucose, occult, mixed: 58% worsened, 39% static, remainder improved not resolved.

nodular/fibroblastic: 69% complete resolution

42

TABLE 56-3. Summary of Adjunctive Therapies Published for the Treatment of Periocular Sarcoid—cont’d


Treatment


Autologous tumor vaccine

6 on head 3 verrucose, 1 fibroblastic, 2 mixed

Surgical debulking, autologous vaccine made from minimum 10 g tumor tissue with tuberculin adjuvant, injected intradermally in both sides of neck 1 to 2 weeks following tumor excision, minimum 3 treatments, 4 weeks apart until healing is complete

no recurrence in 12 to 30 months in 3 horses treated for the first time, 9 to 48 months nonrecurrence in 3 animals treated with already-recurrent disease

110

gamma radiation

2 not specified Debulking of large tumors, implantation of 0.8-mm diameter 198Au grains delivering total dose of 70 gy

no recurrence in 18 months and 3 years

21

14 periorbital not well defined; 6 defined as T2 = 2 to 5 cm diameter or minimal invasion, 8 defined as T3 = >5 cm diameter or subcutaneous invasion

Large tumors debulked 52 to 76 gy total dose administered over 4 to 14 days using ribbons containing 1-cm spaced 192Ir seeds placed at 0.75 to 1.25 cm intervals in a single or double plane

no recurrence in 6 to 41 months, 1 year nonrecurrence 94%

111

63 (27 recurrent)

not well defined: 12 = T1 (<2 cm diameter), 27 = T2 (2 to 5 cm diameter), 24 = T3 (>5 cm diameter)

Mean radiation dose of 62.7 gy administered over 4.8 to 8.9 days using ribbons containing 1 cm spaced 192Ir seeds placed at 0.8 to 1.2 cm intervals in a single or double plane

Mean nonrecurrence of 49 months, 1 year nonrecurrence 86.6%, 5 year nonrecurrence 74%

100

66 nodular, fibroblastic, mixed

192Ir rods delivering 70 to 90 gy, in situ for 10 to 14 days

1 year follow-up: 100% no recurrence

Long-term follow-up (3 to 14 years): 98% no recurrence

42

8 nodular, fibroblastic, mixed, verrucose

Implanted 192Ir rods delivering 45 to 70 gy

Median nonrecurrence rate of 14.5 months

112

Beta radiation 3 Single/superficial verrucose, occult

Strontium plaque wand delivering 100 gy over 5 days (5 minutes twice daily)

1 to 4 year follow-up: no recurrence at treated site

42

AW4-LUDES, A Derek Knottenbelt homemade cocktail; BCG, Bacille Calmette-guérin.

TABLE 56-3. Summary of Adjunctive Therapies Published for the Treatment of Periocular Sarcoid—cont’d

eyelid function is compromised, topical artificial tear supple-ment ointment should be applied regularly to the corneal surface to prevent corneal desiccation.5 Antibiotics may be required as prophylaxis in the perioperative period or to address active or suspected infection. The hospitalization status and demeanor of the horse along with the results of cytological examination, cultures, and sensitivity testing, if available, will factor into selection of antibiotic class and route of administra-tion. A subpalpebral lavage device is frequently used to deliver liquid topical medications and is particularly helpful in frac-tious patients. Further discussion of antibiotic selection is pro-vided in Chapter 7 and in current ophthalmology texts.

Systemic anti-inflammatory medications should be consid-ered in the treatment of adnexal disease, particularly following trauma and surgery. Perioperative flunixin meglumine can be administered intravenously, intramuscularly, or orally (maximum dosage 1.1 mg/kg every 12 to 24 hours for approxi-mately 24 to 48 hours, followed by 0.5 mg/kg for up to 5 days).52 Phenylbutazone can be administered intravenously or orally (maximum dosage 4.4 mg/kg every 12 hours for 24 to 48 hours, followed by 2.2 mg/kg every 12 hours for up to 5 days). Systemic nonsteroidal anti-inflammatory drugs (nSAIDs) have been associated with renal and gastrointestinal damage;53 there-fore, maximum doses should be used for a short duration, and


TABLE 56-4. Basic Equine Adnexal Surgery Pack

Instruments Use Quantity

Backhaus towel clamps 4Mayo scissors 1Metzenbaum scissors 1Suture scissors (any type) 1Stevens tenotomy scissors (10 cm, straight or curved) Fine tissue dissection 1no. 64 Beaver blade and/or no. 15 scalpel blade 1Beaver handle (12.5 cm) and/or Bard-Parker scalpel handle 1Mosquito forceps 4Brown-Adson tissue forceps (16 cm) 2Bishop Harmon forceps (9 cm, 1 × 2 0.5-mm teeth) Fine tissue manipulation 1Cilia forceps Removal of ectopic cilia and distichia after

treatment1

Eyelid speculum (Barraquer, guyton-Park, or Williams) Eyelid retraction 1Castroviejo or Jameson caliper Measurement of lesions 1Derf needle holder 1Castroviejo needle holder (14 cm, straight or curved, with

or without lock)Manipulation of small needles 1

Irrigation cannula Lubrication of the corneal surface 2-4Jaeger lid plate Protection of cornea during eyelid incision 1Desmarres chalazion clamp Lid immobilization 1

Figure 56-6. Recommended surgical instruments for eyelid surgery. 1, Backhaus towel clamps (4); 2, mosquito hemostats (4); 3, suture scissors; 4, Mayo scissors; 5, Metzenbaum scissors; 6, Stevens tenotomy scissors; 7, Derf needle holder; 8, Castroviejo needle holder; 9, Bard-Parker scalpel handle; 10, Beaver scalpel handle; 11, cilia forceps; 12, Bishop-Harmon forceps; 13, Brown-Adson forceps (2); 14, Jaeger lid plate; 15, calipers (Jameson); 16, irrigation cannula; 17, Bard-Parker blade (No. 15); 18, Beaver blade (No. 64); 19, Desmarres chalazion clamp; 20, eyelid speculum (Guyton-Park).

1

11 12 13 14 15 16 17 18 19 20

2 34 5

6 7 8 9 10


the doses should be reduced as soon as clinically indicated. Particular caution should be used in patients with systemic ill-nesses such as dehydration.

Surgical TechniquesFor most adnexal procedures performed under general anesthe-sia, the horse is placed in lateral recumbency with the nose ele-vated using foam wedges or sandbags to maintain the palpebral fissure in a horizontal position. The periocular area is clipped and cleaned using a 1 : 50 dilution of 10% povidone-iodine solu-tion (Betadine, Purdue Pharma, Stamford, CT). The conjunctival sac should also be rinsed with similarly diluted povidone-iodine solution and the area subsequently irrigated with sterile physi-ologic saline. Cotton or paper quarter drapes should be used surrounding the eye, and their size should be sufficient to prevent contamination from the surrounding surgically unprepared skin of the head and neck. A second paper or plastic adhesive fenes-trated drape is placed over the quarter drapes.

Temporary and Permanent Tarsorrhaphy

A tarsorrhaphy is indicated to protect the cornea in cases of facial nerve paralysis or in other situations where blinking is impaired (e.g., severe eyelid trauma). Tarsorrhaphy may provide additional support to the cornea following intraocular surgery.

Temporary tarsorrhaphy is the most frequently used technique and can be performed under general anesthesia or using stand-ing sedation and local anesthesia. The eyelids should be surgi-cally prepared. Three or four horizontal mattress sutures using 2-0 or 3-0 monofilament nylon are usually placed, starting the sutures in the upper eyelid (Figure 56-7). The eyelid sutures should emerge at the meibomian gland orifices (the “gray line”) so that neither eversion nor inversion of the eyelids occurs, both of which can predispose to corneal abrasion. The medial canthus can be left slightly open to facilitate the application of topical ophthalmic ointments. Plastic tubing or buttons should be used as stents to prevent the sutures from tearing through the eyelid.

Partial permanent tarsorrhaphy may be indicated in cases of prolonged facial nerve paralysis. In this procedure, a limited length of the eyelid margins is excised and sutured together, resulting in surgical apposition (Figure 56-8). The procedure otherwise is similar to performing a temporary tarsorrhaphy, although sutures can be removed after 10 to 14 days. If the underlying disease process resolves and the tarsorrhaphy is no longer required, the site of apposition is incised using scissors to restore a normal palpebral fissure.

Entropion

Entropion is an inward turning of the eyelid. It is uncommon in horses relative to other affected species, but is most fre-quently seen in foals.54,55 Entropion can be congenital (secondary to microphthalmia or atypical development5) or acquired (sec-ondary to trauma, scarring, dehydration or wasting, phthisis bulbi, or prolonged blepharospasm) and can affect one or both eyelids. The lateral margin of the lower eyelid is most com-monly affected. Entropion can result in contact between the haired skin or cilia and the cornea or conjunctiva, causing irrita-tion (trichiasis). The most common presenting signs include ocular discomfort (blepharospasm, lacrimation), keratitis, or

Figure 56-7. Temporary tarsorrhaphy. A, Sutures should be preplaced to distribute tension. B, Sutures should be placed at partial thickness, crossing the eyelid margin at the level of the meibomian gland openings. C, Sutures are tied. The use of stents reduces the risk of sutures cutting into the eyelids.

A B

C

conjunctivitis. Topical lubricants, used as a protective barrier for the cornea, may be sufficient to manage mild transient cases of entropion in foals,54 although some require the placement of temporary everting sutures.

EVERTING SUTURESThis procedure will temporarily limit corneal irritation secondary to the entropion. If the entropion is persistent, permanent surgi-cal correction may be warranted. Vertical mattress sutures are placed using monofilament nonabsorbable suture (e.g., 2-0 to 4-0 monofilament nylon). To accurately place the sutures, the entropion is everted to a normal position and a single vertical bite of eyelid skin is taken approximately 1 to 2 mm from the eyelid margin (Figure 56-9). A similar vertical bite of distal eyelid skin is taken. The distance between the bites determines the extent of eversion of the eyelid, so this bite should be posi-tioned with care, and the suture must be replaced if insufficient or excessive eversion is achieved once the suture is tied. Sutures should be placed at approximately 0.5-cm intervals along the area of entropion. Care should be taken to ensure that the cut ends of the sutures are not at risk of irritating the cornea, and cyanoacrylate glue can be applied to the knots to ensure they remain in place.52 Sutures are typically removed after 2 to 4 weeks.52

MODIFIED HOTZ-CELSUS PROCEDUREThis procedure should be performed when permanent correction is required. In foals, this procedure should be performed as late in life as possible because of the risk of overcorrection resulting


Figure 56-8. Permanent tarsorrhaphy. A, Opposing areas of eyelid margin (approximately 3 mm long) are excised with a No. 11 Bard-Parker scalpel blade. B, Sutures are placed in the areas of excised margin. Sutures should be left in place for 3 weeks to allow eyelid adhesion.

A

B

Figure 56-9. A, Entropion of the lower eyelid. B, Temporary stay sutures for correction of entropion. Vertical mattress sutures are placed perpendicular to the eyelid margin. The initial bite is taken close (2 to 3 mm) to the eyelid margin. Sutures should be preplaced to distribute tension equally. Knots should be placed away from the eyelid margin to avoid contact with the cornea.

A

B

Figure 56-10. Modified Hotz-Celsus procedure for entropion repair. A, The initial incisions of the skin and orbicularis oculi muscle are made with a scalpel. B, The skin and superficial orbicularis oculi muscle are excised with scissors. C, A single-layer closure, starting at the center, incorporates both skin and orbicularis oculi muscle. D, Postoperative appearance.

A

BC

D

from subsequent growth of the head and face. To effectively plan the extent of surgical correction required, topical anes-thetic should be applied and a motor nerve block should be performed to eliminate any spastic entropion related to ocular pain and determine the true extent of the anatomic abnormality.5,56

A Jaeger lid plate can be used to support the eyelid, and helps to improve the accuracy of the incision. An incision is made through the skin and orbicularis oculi muscle, parallel to and approximately 2 to 3 mm from the eyelid margin (Figure 56-10). A second elliptical incision is made proximal to the initial incision, and the skin and orbicularis oculi muscle between the incisions is excised. The distance between the two incisions determines the extent of correction of the entropion. Care should be taken not to remove excessive skin initially, because further skin can be subsequently removed. A slight undercorrection is usually appropriate because scarring will increase correction.5,56 Closure is performed using 4-0 to 6-0 polyglactin 910 suture in a simple-interrupted pattern, with sutures oriented radially away from the cornea. Sutures are placed initially at the widest central portion of the incision to determine the degree of correction. Suture tags should be ori-ented to prevent contact with the corneal surface. If too little tissue is removed, undercorrection will result in persistent entropion. Ectropion caused by overcorrection can cause expo-sure keratitis and ulceration.56 Significant eyelid swelling is


ulceration if untreated. Cilia can be removed under general anesthesia using an operating microscope. The cilia follicle is destroyed, preventing further regrowth using electroepilation or cryotherapy. If cryotherapy is used, a 4-mm probe is placed on the palpebral conjunctival surface, approximately 3 to 4 mm from the eyelid margin (at the base of the meibomian glands). Two freeze-thaw cycles should be completed to maximize destruction of the follicles. Cilia should not be resistant to epila-tion if effective follicular destruction has been achieved. Cilia too short to be visualized at the time of surgery cannot be treated; therefore the potential for repeated surgeries should be discussed with the owner. Other treatment options include partial tarsal plate excision58 (although significant eyelid scar-ring can ensue) and for focal areas, wedge excision.

Ectopic Cilia

Ectopic cilia are also rare in horses and result from aberrant eyelid cilia emerging through the palpebral conjunctiva, causing considerable corneal irritation. In one series of seven cases, ectopic cilia were most common in the upper eyelid between the 10 o’clock and 2 o’clock positions.59 For ectopic cilia, the treatment of choice is surgical excision.59 The eyelids are immo-bilized using a Desmarres chalazion clamp, followed by sharp excision of the surrounding conjunctiva, meibomian gland, and cilia follicle en bloc using a Beaver blade (no. 6500). Other treatment options include cryotherapy and electroepilation.

Repair of Eyelid Lacerations

Eyelid trauma is relatively common because of the exposure of the wide-set equine eye and hazards of confinement manage-ment. It should be established whether lacerations are full or partial thickness. The eyelids are highly vascular and will bleed extensively and become edematous following trauma. Cold packs applied to the eye for 10 minutes, four to six times a day can help to reduce swelling if tolerated. Anti-inflammatory and prophylactic antibiotic drugs are frequently indicated. The globe should be carefully examined for other trauma, and careful palpation should be performed to evaluate any orbital or facial fractures. Radiography and other imaging methods (MRI, CT) should be considered for confirmation if fractures are suspected. A thorough evaluation for potential foreign bodies should be performed. Lacerations affecting the medial eyelids may involve the nasolacrimal apparatus. nasolacrimal patency should be confirmed before closure, and nasolacrimal lacera-tions should be treated as described later.

Lacerations should be thoroughly flushed with a 1 : 50 dilu-tion of 10% povidone-iodine solution followed by sterile physi-ologic saline before closure. All lacerations should be surgically managed using a two-layer closure, because healing by second intention can create eyelid abnormalities resulting from signifi-cant proud flesh and scar formation. Fresh lacerations can be closed immediately but long-standing, potentially infected lac-erations should be treated with topical and systemic antibiotics for several days before débridement and closure. Closure can be performed using general anesthesia or with standing sedation and local anesthesia. Débridement of necrotic tissue or exten-sive granulation tissue is necessary, but excessive débridement should be avoided because of the limited tissue available for closure. Tissue-loss defects affecting less than one third of the eyelid margin can be closed using direct apposition, whereas

common after surgery and generally resolves within the first 2 weeks postoperatively.

Ectropion

Ectropion is an out-turning of the eyelid. This results in increased exposure of the cornea and conjunctival surfaces that may result in corneal desiccation and inadequate distribution of tears. Ectropion is most commonly associated with scar formation secondary to trauma or previous surgery. The V-to-Y–plasty is useful to correct ectropion (Figure 56-11). A V-shaped incision is made in the eyelid skin, proximal to the eyelid margin, and underlying scar tissue is removed. The incision is then closed as a Y, causing the eyelid margin to roll in immediately adjacent to the surgical site, correcting the ectropion.

Distichia

Distichia are rare in horses and result from aberrant eyelid cilia that emerge from the eyelid margin, usually from the meibo-mian gland orifices.57 They can cause corneal trauma and

Figure 56-11. V-to-Y correction for ectropion. A, The area of ectropion is identified. B, The V-incision is made with a scalpel. C, The skin flap is elevated, and underlying cicatricial tissue is excised using scissors. D, The skin flap is advanced to relieve skin tension. Closure is performed in a Y pattern.

A

B C

D

Area ofectropion


Figure 56-12. Repair of eyelid laceration. A, Minimal débridement is performed. B, Closure is performed in two layers, starting at the eyelid margin to ensure optimal alignment. C and D, Skin closure is accom-plished with simple-interrupted sutures (4-0 or 5-0). A figure-of-eight suture pattern is useful for closure of the eyelid margin, because it allows suture placement on the eyelid margin, with placement of the knot away from the globe.

A

B C

D

tissue-loss defects affecting more than one third of the eyelid margin or those close to the lateral or medial canthi may require more complex blepharoplasty procedures (see later). Closure should be performed in two layers, by closing the pal-pebral conjunctiva first, using a simple-interrupted or simple-continuous suture pattern with 4-0 to 6-0 absorbable suture material, such as polyglactin 910 (Figure 56-12). If the site is infected, nonabsorbable suture material should be used and sutures should be removed after 10 to 14 days. Knots should be positioned away from the palpebral surface of the conjunctiva. The eyelid skin is closed in a simple-interrupted pattern, starting at the eyelid margin to ensure appropriate margin apposition and healing. A figure-of-eight suture pattern (see Figure 56-12 and Figure 56-13) is useful to prevent the suture tags from abrading the cornea. The rest of the eyelid skin is sutured in a simple-interrupted pattern.

AFTERCAREA protective eye mask with a hard cup may be necessary to prevent rubbing postoperatively. If an eye mask is not adopted, a fly mask should be used until healing is complete.

Alternatively, fly repellent ointment can be applied to the skin adjacent to the surgical site.5 Significant eyelid swelling is common after surgery (Figure 56-14) and generally resolves within the first 2 weeks postoperatively.

Reconstructive Blepharoplasty Techniques

More extensive eyelid lacerations or closure of large defects fol-lowing removal of neoplasia (removal or loss of greater than one third of the eyelid margin) warrant reconstructive

Figure 56-13. The figure-of-eight suture pattern for optimal eyelid margin apposition. A, Lateral view. The suture is placed in the numerical order shown, maintaining equal distances with each suture bite. B, View from above, illustrating the placement of the suture at the gray line in the eyelid margin (white arrows). C, Lateral view. The suture is tied and suture tags are positioned away from the corneal surface. The rest of the laceration can be closed using simple interrupted skin sutures. D, Shown from above, demonstrating apposition of the eyelid margin.

C

D

2

4

3

1

A

B


Figure 56-14. A, Example of an eyelid laceration before repair in a horse. B, A two-layer closure was performed in the upper palpebral conjunctiva and palpebral skin using absorbable suture material. Wound dehiscence is a risk because of extensive vascular injury.

A B

blepharoplasty to approximate normal eyelid conformation. This type of surgery frequently warrants general anesthesia.

SLIDING SKIN FLAPA frequently used blepharoplasty technique is the sliding skin flap (Figure 56-15). Following neoplasia excision or débride-ment of lacerations, vertical incisions are made in the eyelid skin that extend in height approximately twice the width of the eyelid defect. Slightly diverging incisions compensate for some

expected wound contracture. Small triangular portions of skin (Burow’s triangles) are excised at the base of the vertical inci-sions (see Figure 56-15, A). These triangles allow closure without skin folds (dog-ears) and help to distribute tension; they should approximate half to the full height of the vertical incision. The surrounding skin, skin flap, and conjunctiva are undermined using blunt dissection, and the skin flap is advanced to the eyelid margin (see Figure 56-15, B). Wound contracture should be anticipated, and a slight initial advancement and fixation of the flap past the eyelid margin may provide a better ultimate cosmetic result. The flap is sutured to the conjunctiva at the eyelid margin and to the adjacent skin in a simple continuous pattern using 4-0 to 6-0 absorbable suture (polyglactin 910) (see Figure 56-15, C). A temporary tarsorrhaphy may provide addi-tional support during healing.

CONJUNCTIVAL ADVANCEMENT FLAPIn cases of neoplasia or trauma with extensive conjunctival involvement, a conjunctival advancement flap from the oppos-ing eyelid may be required (Figure 56-16). A sliding skin flap is created as detailed previously (see Figure 56-16, A). Palpebral conjunctiva from the opposing eyelid is incised approximately 2 to 3 mm from the eyelid margin, measuring the same width as the eyelid defect, and vertical incisions are made toward the conjunctival fornix (see Figure 56-16, B). The conjunctival flap is sutured to the remaining conjunctiva in the eyelid defect (see Figure 56-16, C). Closure of the sliding skin flap is as previously described. A temporary tarsorrhaphy is required to alleviate tension on the conjunctiva. A second procedure is performed to transect the base of the conjunctival flap and remove the tarsor-rhaphy, approximately 1 month following the initial surgery (see Figure 56-16, F). This procedure can generally be performed on the standing, sedated horse using local anesthesia.

FULL-THICKNESS EYELID GRAFTA full-thickness eyelid graft may be required for extensive lesions of the eyelid skin, where sufficient skin cannot be ele-vated using a sliding skin flap (Figure 56-17). This technique is

Figure 56-15. Sliding skin flap to repair eyelid defects. A, Proportions of incisions should be ab = bc = cd = de. B, Equilateral triangles of skin are excised, as is the affected portion of eyelid. The skin flap and adjacent skin are undermined with scissors. Adjacent conjunctiva is mobilized and closed with absorbable suture (polyglactin 910 [6-0 Vicryl]). C, The skin flap is advanced, and the leading edge of the flap is sutured to the conjunctiva and skin.

A

B C


Figure 56-16. Tarsoconjunctival advancement flap. A, A skin advancement flap is prepared as in Figure 56-15. B, Conjunctiva of the upper eyelid opposite the defect is incised 3 to 4 mm from the eyelid margin and is undermined to create a flap. C, The conjunctival flap is advanced and sutured into the defect. D, The skin flap is advanced and sutured in place. E, A temporary tarsorrhaphy relieves tension on the flaps. The use of stents helps to distribute tension. F, After 4 weeks, the tarsorrhaphy is removed and the conjunctival flap is severed at the level of the eyelid margin. The con-junctiva and skin are apposed with a continuous pattern of 6-0 or 7-0 absorbable suture.

A B C

D E F

Figure 56-17. Full-thickness eyelid graft. A, The area of affected lower eyelid is excised. B, The upper eyelid is excised 5 mm above the eyelid margin opposite the defect. C, The graft is split into skin and tarsoconjunctival layers. The graft is advanced under the eyelid margin and sutured in place. D, The bridging eyelid margin is sutured to the graft. A temporary tarsorrhaphy alleviates tension on the graft. E, After adequate healing has occurred, the graft is severed along the intended eyelid margin. F, The conjunctiva and skin are apposed along the eyelid margin with a continuous suture pattern. The skin flap is sutured to the bridge to complete the closure.

A C

D E F

B


located in the inferomedial orbit between the lower eyelid and the globe. This structure is well developed in the horse and moves passively in a temporal and superior direction to cover the anterior surface of the eye with the contraction of retrobul-bar muscle (abducens nerve, Cn VI) and retrograde movement of the globe. The third eyelid can protrude to cover the majority of the corneal surface.65

The third eyelid has a number of functions including the production of a portion of the aqueous layer of the tear film via the nictitans gland and the distribution of tears via passive movement across the globe following globe retraction. Others have suggested that the equine third eyelid provides globe protection, particularly while grazing,3,63 and has a role in

easier to perform on a lower eyelid defect using the more mobile and extensive upper eyelid as the donor tissue. A sliding skin flap of the lower eyelid can provide partial closure of the defect to be grafted. The width of the graft should be 1 to 2 mm larger than the width of the defect in the opposing eyelid margin. The donor eyelid is incised approximately 5 mm from the eyelid margin (to spare the meibomian glands) (see Figure 56-17, B). The flap should be split into skin and muscle, and tarsoconjunc-tival portions to aid mobility of the tissue. The tarsoconjunctival portion of the graft is sutured to the conjunctival defect in the lower eyelid using a simple-continuous suture of 6-0 polyglac-tin 910 (see Figure 56-17, C). The skin portion of the graft is sutured to the lower eyelid skin defect using 4-0 nonabsorbable suture (e.g., monofilament nylon) (see Figure 56-17, D). The bridge in the upper eyelid is sutured to the graft to prevent retraction, and a temporary tarsorrhaphy is placed. In a second procedure, the flap is transected along the new eyelid margin (see Figure 56-17, E), and the lower eyelid conjunctiva and skin are sutured using 6-0 absorbable suture material (polyglactin 910) in a simple-continuous pattern (see Figure 56-17, F). The donor flap is sutured back within the upper eyelid.

RHOMBOID GRAFT FLAPRhomboid and modified rhomboid flaps are used to treat large periocular skin defects in human patients.60 A large periocular or eyelid margin defect can be grafted by generating a rhombus, or equal-sided parallelogram, which can be rotated to cover the eyelid defect (Figure 56-18). The rhombus can be constructed as a square, or with sides at approximately 60 and 120 degrees. Once the defect is created, two incisions are made in the distal eyelid skin to form two additional sides of the rhombus (see Figure 56-18, B). The skin is undermined using blunt dissection and the rhombus is rotated 90 degrees to fill the defect (see Figure 56-18, C). Conjunctiva from the distal palpebral or bulbar surfaces should be advanced to the new eyelid margin. Simple interrupted or simple continuous sutures of 4-0 to 6-0 absorbable suture material are used to suture the conjunctiva to the new eyelid margin and to suture the graft in place (see Figure 56-18, D).

SLIDING Z FLAPMass excision or tissue loss at the lateral canthus can be recon-structed using a sliding Z flap (Figure 56-19). The lesion should be fully excised or débrided, and the surrounding skin and tarsoconjunctiva should be separated using blunt dissection (see Figure 56-19, B). Triangles of skin are excised superior and inferior to the defect (see Figure 56-19, C). The skin is advanced to cover the defect. The new portion of eyelid margin is created by suturing skin and conjunctiva together using 4-0 to 6-0 absorbable suture material (polyglactin 910). The remaining skin is sutured in a similar manner (see Figure 56-19, D).

OTHER RECONSTRUCTIVE PROCEDURESnumerous alternative blepharoplasty procedures with potential application to equine cases can be found in ophthalmology textbooks.52,61-64

NICTITATING MEMBRANEAnatomy and PhysiologyThe third eyelid (i.e., nictitating membrane, membrana nicti-tans) is a mobile protective structure covered by conjunctiva

Figure 56-18. Rhomboid graft flap. A, The rhomboid is aligned with one side along the position of the eyelid margin. Sides of the rhomboid are equal. The replacement flap is incised on a line (A1) continuous with the diagonal of the rhomboid, for a distance equal to the sides of the rhomboid. The second incision (A2) is also equal in length and is placed parallel to the side of the rhomboid. B, The lesion is excised and con-junctiva is mobilized to cover the replacement flap. C, The flap is dis-sected free from underlying tissue and rotated into position. D, The flap is sutured in position with the leading edge forming the new eyelid margin. (Angles 1 and 2 are indicated on B and D to aid in orientation.)

AA1

A2

BC

D


Figure 56-19. Sliding Z flap. A, Growths of the lateral eyelid can be removed en bloc. The triangular areas of skin to be removed adjacent to the defect are marked. Excision of these flaps facilitates skin mobiliza-tion. (The bases of the triangles align with the diagonal of the defect.) B, Adjacent skin is undermined. C, Equivalent triangles of skin are excised. (Cut edges A, A′, B, and B′ are shown to aid in orientation for advancement of the flap.) D, The flap is advanced and sutured in place.

A

B C

D

immunologic protection including the secretion of immuno-globulin A.66

Structural support of the third eyelid is provided by a T-shaped cartilage, in which the horizontal margin of the T is positioned close to the leading edge of the third eyelid (Figure 56-20), and both ends have a characteristic hook shape.67 The cartilage contains a substantial elastic component67 and its shape closely matches the curvature of the globe. The vertical base of the cartilage is surrounded by a large amount of fat and the seromucoid gland of the nictitans. The surfaces of the third eyelid are covered with conjunctiva, containing mucus-secreting goblet cells and intraepithelial glands at the base. The bulbar substantia propria of the third eyelid contains lymphoid tissue.

Sensory innervation is provided by the infratrochlear nerve, a branch of the ophthalmic division of the trigeminal nerve (Cn V).3,67 Retraction of the third eyelid is partially controlled by sympathetic tone in the orbital smooth muscles; loss of tone results in the protrusion that accompanies Horner’s syndrome and associated enophthalmos. Vasculature is supplied by the malar artery, a branch of the internal maxillary artery.3

Ophthalmic Examination Techniques and Diagnostic ProceduresIn the investigation of third eyelid abnormalities, a systematic approach to diagnosis should always be adopted, including a full bilateral ophthalmic and systemic examination. Particularly important is the palpation of regional lymph nodes if third eyelid masses are noted. In cases of corneal or conjunctival disease, the third eyelid should be carefully examined to rule out any contributing lesions. Manual retropulsion of the globe through the superior eyelid causes protrusion of the nictitating membrane, allowing examination of the palpebral surface and leading edge. Topical anesthetic drops and sedation restraint may be required to examine the bulbar surface closest to the globe (see “Eyelids,” earlier). Forceps that cause minimal tissue trauma (such as Von graefe fixation forceps) can be used to retract the third eyelid and examine the deep conjunctival for-nices and the bulbar surface. The bulbar surface should be examined if a foreign body is suspected or in suspected cases of conjunctival parasites (e.g., Thelazia spp.). Digital palpation may also be necessary to fully evaluate the extent of any observed masses.

Figure 56-20. A schematic diagram of the histologic features of the third eyelid.

Palbebralconjunctivalsurface

Third eyelidcartilage

Bulbarconjunctival

surface

Lymphoid tissue

Gland of thethird eyelid


from the palpebral surface of the third eyelid, approximately 4 to 5 mm from the leading edge, taking care not to penetrate the full thickness of the bulbar surface. Because sutures can tear through conjunctiva, encircling the T-cartilage of the third eyelid helps to retain sutures. The final bite of suture enters the upper conjunctival fornix and exits the haired skin of the supe-rior eyelid. Alternatively, three or four horizontal mattress sutures may be used. Stents of buttons or polyethylene tubing should be used to prevent damage to the eyelid skin. The suture tags can be tied and left long to allow the flap to be sporadically lowered. A subpalpebral lavage device can be placed at the same time the third eyelid flap is constructed.

COMPLICATIONSThe cartilage of the third eyelid can become permanently deformed, causing corneal abrasion, and in severe cases this warrants third eyelid removal.56 If stents are not used, ulcer-ation of the skin around the sutures can be severe. If inap-propriately placed, the suture can cause additional damage to the cornea.

Excision of the Third Eyelid

The third eyelid is a common site of adnexal neoplasia, and it is particularly susceptible to the development of squamous cell carcinoma.24,30,31,36 Squamous cell carcinoma often initially appears as an area of hyperemia, becoming raised and in some cases developing a papillomatous appearance (Figure 56-21). Tumors of vascular origin, including hemangioma, hemangiosarcoma69-71 and lymphangiosarcoma72 have also been described. Hemangiomas and hemangiosarcomas often result in a hemorrhagic ocular discharge.70,71 Other neoplasms reported include basal cell tumor73 and lymphsarcoma.23,74

Excision is the treatment of choice for confirmed or suspected neoplasms affecting the third eyelid. A success rate of

Diagnostic procedures such as cytology, fine needle aspira-tion, biopsy, and bacterial culture and sensitivity testing should be considered as necessary.

Anesthetic ConsiderationsMost third eyelid procedures can be performed on the standing, sedated horse, although general anesthesia can be performed if deemed necessary. The sensory infratrochlear nerve block provides anaesthesia to the third eyelid and can be used in combination with topical anesthesia. However, topical and local anesthesia will not desensitize the deep portions of the third eyelid; therefore, an additional retrobulbar block should be considered (see Chapter 55) when removing the third eyelid or making deep incisions or crushing tissues. A line block of local anaesthetic at the base of the third eyelid can provide additional anesthesia when performing removal or biopsy.

Required Surgical EquipmentTable 56-5 outlines some additional equipment that may be useful when performing third eyelid surgery.

Surgical TechniquesThird Eyelid Flap

There are limited indications for the use of a third eyelid flap. unlike conjunctival pedicle grafts, third eyelid flaps cannot replace or support damaged corneal stroma and do not provide any serum-derived factors that assist in corneal healing. Corneal bullae can develop secondary to extensive corneal edema, and a third eyelid flap can provide tamponade of the cornea while facilitating treatment application to the conjunctival sac. Other indications include physically supporting a weakened cornea following a conjunctival graft, reducing contamination of an injured cornea, or reducing evaporative tear film loss secondary to exophthalmos or facial nerve paralysis.56 Flaps are typically contraindicated in cases of deep ulceration or corneal melting, because they may prevent appropriate penetration of topical medications and promote the retention of inflammatory cells and bacteria adjacent to the corneal surface.68 The flap also obscures visual examination of the cornea and prevents evalu-ation of progression or healing, unless sutures are placed to facilitate sporadic lowering of the flap.

A flap is placed either under general anesthesia or standing sedation and local anesthesia. A single suture of 2-0 to 3-0 nonabsorbable material is inserted from the haired skin of the upper eyelid into the upper conjunctival fornix. A bite is taken

TABLE 56-5. Additional Instruments Particularly Useful for Equine Third Eyelid Procedures

Instruments Use Quantity

Large curved hemostat forceps

Crushing of edges of third eyelid before removal

4

Allis tissue forceps Third eyelid retraction 2-4Sterilized buttons/

sections of plastic tubing

Stents for third eyelid flap

4

Figure 56-21. Typical verrucose appearance of a squamous cell carci-noma affecting the leading edge of the nictitating membrane.


using 5-0 or 6-0 polyglactin 910 in a simple-continuous pattern to reduce the risk of orbital fat prolapse.56 All tissue removed should be submitted for histopathologic examination for deter-mination of tumor type and surgical margins.

AFTERCARETopical antibiotic (with or without a steroid) ointment should be applied to the eye for 5 to 7 days following surgery. Flunixin meglumine administration for the first 3 to 5 days will reduce inflammation and discomfort. Although the nictitans gland is removed when excising the third eyelid, very few equine eyes develop tear production deficits,75 and long-term lubricants are not usually required.

COMPLICATIONSComplications are rare but include orbital fat prolapse, kerato-conjunctivitis sicca, and superficial keratitis.56 The absence of a third eyelid can impair globe protection and result in mild chronic ocular irritation and discharge.56

Lacerations

Lacerations affecting the third eyelid should be treated surgi-cally to reappose the edges of conjunctiva and restore the margin of the third eyelid. Apposition of the margin should precede proximal sutures, because inappropriate apposition may result in scarring and corneal trauma. Sutures of 6-0 or 7-0 polyglactin 910 should be placed emerging from the palpebral surface. Sutures of the bulbar conjunctiva should be placed

Figure 56-22. Surgical removal of the third eyelid. A, Local anesthetic is injected at the base of the third eyelid. B, The nictitating membrane is lifted from the fornix with forceps. C, Two hemostats are placed across the base of the third eyelid. D, The third eyelid is excised along the two hemostatic forceps.

A B

C D

approximately 90% has been previously reported using surgical excision alone,30,36,75 although adjunctive therapies such as gamma- or beta-irradiation have been described in a small number of cases with limited effects on recurrence rates.30 A recent study has shown that topical mitomycin C (0.2 mL of 0.04% formulation every 6 hours in 1-week cycles) can be effec-tive alone or in combination with surgical excision.76 Cryother-apy alone or as an adjunct to surgical excision should be avoided in cases of squamous cell carcinoma, because it has been shown to increase the risk of local tumor recurrence by 2.5 times.30 If the tumor extends beyond the third eyelid, alternative or addi-tional surgical and adjunctive therapies may be necessary. Partial excision is not recommended because of the recurrence risk75 and the cut edge of the third eyelid cartilage can abrade the cornea. Excision can be performed under general anesthesia but is more commonly performed on the standing, sedated horse with local anesthesia.75 A combination of auriculopalpebral, infratrochlear, and zygomatic nerve blocks; local infiltration; and topical analgesics usually provide adequate analgesia (Figure 56-22), although a retrobulbar block may be required to provide additional analgesia (see Chapter 55).

The third eyelid is grasped on the T-cartilage using Allis tissue forceps and elevated. Large hemostatic forceps are advanced from the medial and lateral edge along the base of the third eyelid until the tips are apposed proximal to the gland of the nictitans. All tissue superficial to the hemostatic forceps includ-ing the T-cartilage and gland are removed en bloc using scissors or a scalpel blade. The hemostats are removed after 1 to 2 minutes. The cut edges of conjunctiva can be sutured together


punctum is generally larger, closer to the medial canthus, and farther from the eyelid margin.78 Tear drainage into the puncta occurs via capillary action and blinking.

The nasolacrimal system begins with a pair of nasolacrimal canaliculi connecting the puncta with the nasolacrimal sac. The sac is often poorly defined in horses and lies within the lacrimal fossa of the lacrimal bone. The nasolacrimal duct measures approximately 29 to 33 cm long79 and passes through the lac-rimal canal within the lacrimal bone and maxilla. The duct is narrowest as it exits the lacrimal canal (Figure 56-23).78,79 When performing maxillary trephination or evaluating trauma to this region, the course of the nasolacrimal duct may be predicted by drawing a line from the medial canthus to the infraorbital foramen.78 After exiting the lacrimal canal, the duct continues within the lacrimal groove of the maxilla beneath the mucous membrane of the middle nasal meatus.2 It continues within the basal fold of the ventral nasal concha, where the duct wall becomes irregular as it passes through the vascular plexus of the basal fold. It courses over the nasal process of the incisive bone to end near the mucocutaneous junction in the ventral nasal meatus at the nasal ostium, which is 3 to 4 mm in diameter and visible clinically (Figure 56-24). The nasolacrimal duct may contain blind-ending branches into channels that may not reach the nasal ostium.

Examination TechniquesIn the investigation of nasolacrimal system abnormalities, a systematic approach to diagnosis should always be adopted, including a full ophthalmic and systemic examination. Kerato-conjunctivitis sicca is rare in the horse. When it is present, the neurogenic form is most common and is often seen in combination with facial and/or trigeminal nerve paralysis.80 A complete description of the investigation of dry eye conditions is beyond the scope of this text. However, when investigating corneal surface abnormalities, a Schirmer tear test (Schirmer tear test strips, Schering-Plough Animal Health, Kenilworth, nJ), fluorescein staining, and rose bengal staining should

carefully to avoid contact of suture material with the cornea. Any exposed cartilage should be covered by conjunctiva, par-ticularly on the bulbar surface of the third eyelid.

NASOLACRIMAL SYSTEMAnatomy and PhysiologyPreocular Tear Film

The preocular tear film covers the cornea and conjunctiva and has three components. The outer lipid component is derived from the meibomian (i.e., tarsal) glands and the sebaceous glands of Zeis within the eyelids. The middle aqueous layer is predominantly derived from the lacrimal gland situated in the dorsolateral orbit (between the zygomatic process of the frontal bone and the eye). The secretions from the lacrimal gland enter the lateral part of the superior conjunctival fornix. Smaller con-tributions to this layer are produced by the gland of the third eyelid (i.e., nictitans gland) and the accessory lacrimal glands of the eyelids. The inner mucinous layer is derived from the con-junctival goblet cells and intraepithelial glands within the conjunctiva.

The tear film has many functions including flushing foreign material, lubricating the eye to facilitate the movement of the eyelids and third eyelid, maintaining a refractive corneal surface, delivering nutrients to the cornea and conjunctiva, and facilitat-ing immune protection. In the normal equine eye, a complete recycling of tear volume occurs approximately every 7 minutes.77 The lacrimal lake results from flow of tears across the cornea following blinking and forms along the leading edge of the lower eyelid and adjacent to the inferior edge of the lacrimal caruncle and third eyelid.

Nasolacrimal Drainage System

Horses possess both superior and inferior lacrimal puncta (see Figure 56-1, C). Each punctum is a horizontal slit in the palpe-bral conjunctiva approximately 2 mm in length. The lower

Figure 56-23. Methyl methacrylate cast of the left nasolacrimal duct of a horse. The medial bony orbit and medial wall of the lacrimal canal have been removed. A, Lacrimal sac. B, Course of the duct within the lacrimal bone. C, Narrowing of duct lumen before exiting lacrimal bone. D, Exit of duct from lacrimal bone. E, Compression of duct by cartilage within alar fold. F, Cast within the basal fold. (Reproduced with permission from Latimer CA, Wyman M, Diesem CD, et al: Radiographic and gross anatomy of the nasolacrimal duct of the horse. Am J Vet Res 45:451, 1984.)

FE

DC

B

A


Figure 56-24. Identification and catheterization of the nasal ostium. A, The nasal ostium is visible in the ventral nasal meatus close to the muco-cutaneous junction (white arrow). B, Distal catheterization using a 5-French rubber urinary catheter facilitates retrograde flushing of the nasolacrimal system.

A B

be considered part of the ophthalmic diagnostic workup. A Schirmer tear test value of less than 10 mm/min is considered abnormal in horses and ponies.81 The administration of any topical drops such as tropicamide affect Schirmer tear test values.82 Cytology and bacterial culture and sensitivity testing should be considered in suspected cases of dacryocystitis.

The most straightforward method to evaluate nasolacrimal system patency is to assess the passive drainage of fluorescein to the nasal ostium by instilling fluorescein stain (wet fluores-cein strips or single-use vials containing 2% fluorescein) into the conjunctival sac.54 Positive drainage confirms nasolacrimal patency. A more-invasive method is to perform nasolacrimal cannulation via the upper and lower puncta (see Figure 56-1, C). Sterile disposable cannulas or reusable autoclavable can-nulas can be used for cannulation, which can be performed under topical anesthesia on the standing, sedated horse if neces-sary. Minimal force should be required to achieve drainage through the nasal ostium. The use of fluorescein solution as the flushing medium aids in the positive diagnosis of patency. Ret-rograde flushing techniques can also be performed using a 5- to 6-French pliable urinary catheter (see Figure 56-24, B).

Diagnostic ProceduresDacryocystorhinography

Radiographic methods of dacryocystorhinography have been described that involve cannulating the upper lacrimal punctum and injecting viscous contrast medium before radiography (Figure 56-25).78,83 This technique has been described in the standing horse. Even in unilateral disease, it is advantageous to perform the technique on both nasolacrimal ducts to provide an internal control. Recent work has demonstrated that the nasolacrimal duct of the horse can be evaluated using CT dac-ryocystorhinography (Figure 56-26).84 This technique requires general anesthesia and positioning the horse in dorsal or sternal recumbency. About 5 mL of iodinated contrast medium is injected retrogradely through the nasal ostium.

Endoscopy

Endoscopic evaluation of the nasolacrimal duct has been described in adult horses.79 The portion of the duct within the lacrimal bone is difficult to examine using this method. This procedure may be useful for collecting samples in cases of dac-ryocystitis or aiding the diagnosis and removal of foreign bodies or dacryoliths.

Figure 56-25. Normal right lateral equine dacryocystorhinogram illus-trating the anatomical features shown in Figure 56-23. A, Lacrimal sac. B, Course of the duct within the lacrimal bone. C, Mild narrowing of duct lumen before exiting lacrimal bone. D, Exit of duct from lacrimal bone. E, Compression of duct by cartilage within alar fold. (Courtesy Dr. Anthony Pease.)

E

DC

B

R

A


the eyelids and atresia or agenesis of the duct,87 which should be ruled out by clinical examination, cannulation and flushing of the nasolacrimal system, and/or diagnostic imaging tech-niques. Clinical signs of epiphora or mucopurulent ocular dis-charge are typically first reported by owners in animals ranging from birth to 1 year of age.54,86 Anomalous supernumerary openings of the nasolacrimal system have also been reported.88

Treatment of imperforate nasal puncta can usually be per-formed on the standing, sedated horse. The nasolacrimal duct can be filled with sterile physiologic saline with the addition of dilute fluorescein dye to aid visualization. The mucosa overlying the bleb of fluid within the nasal passage can be incised using a scalpel blade. Alternatively, a catheter (5- to 6-French silicone male urinary catheter86) can be inserted into the upper lacrimal puncta and passed down the duct, and the incision can be made over the palpable end of the catheter. The portion of catheter emerging from the lacrimal puncta should be sutured to the skin of the face (Figure 56-27). The distal portion of catheter can be sutured to the nose or lip or passed through the lateral wall of the nostril86 (see Figure 56-27, B). The catheter is typi-cally maintained in place for 2 to 4 weeks.

Figure 56-26. Transverse computed tomography dacryocystography scan of an equine skull at the level of the caudal maxillary sinus. There is a fracture of the left maxilla with adjacent soft tissue swelling (arrow-head). No disruption of the nasolacrimal duct is evident (arrow). The inset is a close-up of the nasolacrimal canal and duct. (Reproduced with per-mission from Nykamp SG, Scrivani PV, Pease AP: Computed tomography dacryocystography evaluation of the nasolacrimal apparatus. Vet Radiol Ultrasound 45:23, 2004.)

Anesthetic ConsiderationsTopical anesthesia and standing sedation is useful as described earlier. For additional analgesia, a cotton-tipped applicator soaked in proparacaine can be applied directly onto the naso-lacrimal puncta for 2 to 5 minutes before proceeding to its cannulation.

Required Surgical EquipmentCannulas and catheters for cannulation of the nasolacrimal duct are useful. Standard single-use plastic cannulas and auto-clavable steel cannulas are available. For cannulation of the nasolacrimal system to correct nasolacrimal punctal atresia, cardiac catheters of various sizes are useful (no. 4 to 6). A round-tipped, eyed pigtail probe (modified Worst probe) is effective in facilitating the placement of a silicone-tubing stent to treat lacerated nasolacrimal canaliculi.85

Surgical TechniquesImperforate Puncta

The most common defect of the nasolacrimal system in the horse is an imperforate distal nasal punctum.86 Other abnor-malities include imperforate proximal lacrimal puncta within

Figure 56-27. A catheter is sutured to the periorbital skin (A), and skin of the nostril (B) after cannulating and surgically opening an imperforate nasolacrimal duct.

A

B


Atresia of either the upper or lower lacrimal punctum can be treated by cannulation of the patent lacrimal punctum and using a scalpel blade to incise tissue over the bleb created. A silicone stent can be placed to aid healing.

Canaliculorhinostomy may be a surgical alternative for atresia or agenesis of substantial portions of the distal nasolac-rimal duct.89 An 18-gauge, 1.5-inch needle is used to drill into the rostral maxillary sinus, using the lower eyelid canaliculus as a guide; 60-gauge fishing line is used to create a retention sty-lette that remains in place for at least 1 month. Another method of conjunctivorhinostomy is to create a stoma between the inferior conjunctival fornix and the maxillary sinus.90 With both of these procedures, there is a risk of strictures forming in the artificial stoma over time.

Figure 56-28. Repair of the severed lacrimal canaliculus. A, Laceration of the lower eyelid, severing the lacrimal canaliculus. B, A 2-0 nylon suture is passed through the nasolacrimal duct and exits through the wound. A Worst probe is passed through the ventral punctum and draws the suture through the distal portion of the severed canaliculus. C, A fine silicone tube is cut to a taper, tied to the suture, and pulled through the canaliculi. D, The canaliculus and wound are sutured with 6-0 nylon silk. E, The tubing is sutured to the skin of the eyelid and at the nasal end. It is left in place for 3 weeks.

A

B C

D

E

Lacerations

Lacerations of the nasolacrimal system occur most commonly at or near the eyelid margin. Surgical correction is indicated to prevent inappropriate healing or scarring, resulting in blockage of the canaliculus or punctum and resultant epiphora. The repair of nasolacrimal punctal lacerations have been well described in human texts, although no reports for equine naso-lacrimal lacerations were found. A blunt-tipped, eyed pigtail probe is inserted into the unaffected punctum and fed until it exits from the severed end of the canaliculus (Figure 56-28).85 A 6-0 polypropylene suture is placed in the eye of the probe, which is then retracted to draw the suture through to the unaf-fected punctum. The probe is passed through the punctum of the lacerated canaliculus and the suture is again drawn through to exit from this punctum. A silicone stent tube is passed over the suture (the tube cannulates both nasolacrimal canaliculi and puncta) from the unaffected side. The suture material can be tied, maintaining the silicone tubing in place, or it can be removed and the ends of the tube can be sutured together. The canaliculus and eyelid skin are sutured using 6-0 polypropyl-ene. The tube is sutured in place and left for 4 to 6 weeks to maintain patency as the canaliculus heals.91 Topical and/or sys-temic antibiotics should be administered in the postoperative period.

REFERENCES

1. Lemp MA, Wolfley DE: The Lacrimal Apparatus. p. 18. In Hart WM (ed): Adler’s Physiology of the Eye: Clinical Application. 9th Ed. Mosby, St. Louis, 1992

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