Surgery of the eye and its surrounding structures can readily be performed under local anaesthesia. General anaesthesia is reserved for those unable to cooperate, such as children, or those receiving bilateral surgery or complex or lengthy procedures. Routine cataract surgery is usually performed under local anaes-thesia and efforts have concentrated on finding methods that have few serious complications. Occasionally serious systemic complications of ophthalmic local anaesthesia may occur, espe-cially in medically compromised patients. In recognition of this the Joint Working Party report on Anaesthesia in Ophthalmic Surgery1 recommends that an anaesthetist is included in the team managing patients for ocular surgery under local anaesthesia.
Anatomy - with any local anaesthetic technique a detailed knowledge of anatomy is essential (page 379). Motor innervation is from cranial nerves III, IV, VI and VII (Table 1), and sensory innervation is via the ophthalmic and maxillary divisions of cra-nial nerve V (trigeminal) (Table 2).
General considerationsAbsolute contraindications to ocular local anaesthesia are the same as for any local anaesthetic technique: patient refusal,
Caroline Carr, MA, FRCA, is Consultant Anaesthetist and Service Director
at Moorfields Eye Hospital, London. Apart from ophthalmic anaesthesia
her special interest is clinical governance.
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inability to cooperate and lie still, presence of local sepsis, and allergy to the local anaesthetic agents.
Relative contraindications are previous or repeated surgery, when local anaesthesia techniques may become technically dif-ficult, and in the open eye such as a ruptured globe when the contents are at risk of expulsion.
Preoperative assessment: the patient’s concomitant medical conditions should be controlled before surgery. Medical history, examination and special tests are targeted to this end. Of particular relevance to ocular surgery under local anaesthesia are the pres-ence of chronic cough, breathlessness and disorders of movement such as Parkinson’s disease. These must be carefully assessed with respect to the patient’s ability to lie flat and still for the surgery. For patients receiving anticoagulation therapy, their international normalized ratio should be maintained within therapeutic limits (2–3) for ocular surgery under topical, peribulbar or sub-Tenon’s anaesthesia.1 Patients do not need to starve preoperatively.
Choice of anaesthetic: the surgeon’s preference, the intended surgery, the ocular anatomy and the patient’s preference all need
Motor innervation of the eye
Muscle Nerve supply
Inferior oblique Oculomotor (III)
Superior rectus Oculomotor (III)
Inferior rectus Oculomotor (III)
Medial rectus Oculomotor (III)
Levator palpebrae superioris Oculomotor (III)
Superior oblique Trochlear (IV)
Lateral rectus Abducens (VI)
Orbicularis oculi Facial (VII) temporal and
zygomatic branches
Table 1
Sensory innervation of the eye
Structures Nerve supply
Sclera, cornea, iris and ciliary body Short ciliary nerves
to be taken into consideration when choosing the anaesthetic technique.2 These should be considered at the preoperative assessment visit and the technique to be used explained care-fully to the patient and supplemented with leaflets and other patients’ experiences.3 A very anxious patient may be suitable for combined sedation and local anaesthesia. Alternatively, general anaesthesia may be the best option.
Techniques of local anaesthesiaTopical anaesthesia provides good surface anaesthesia of the globe without the complications of a regional block. The patient retains full eye movement. Commonly used for superficial sur-gery of the conjunctiva and cornea, including removal of sutures and small foreign bodies, topical anaesthesia alone is now fre-quently used for cataract surgery.4 With the newer techniques of surgery, akinesia and reduction of intraocular pressure are not of such importance. Patients experience discomfort owing to sensa-tion from the iris and ciliary body,5 but this can be abolished by intracameral preservative-free lidocaine 1%, up to 1 ml.
Local infiltration of the skin with anaesthetic is used for eye-lid surgery in adults. For anaesthesia of deeper structures, the supraorbital and infraorbital branches of the trigeminal nerve are blocked where they emerge from the supraorbital notch and infraorbital foramen. 0.5% bupivacaine, 1–2 ml, with epineph-rine 1:200,000 is injected subcutaneously at each site. To avoid subcutaneous haemorrhage:• aspirin should be stopped 2 weeks preoperatively• warfarin should be stopped 3 days preoperatively• injection into deeper tissues should be avoided• epinephrine 1:200,000 should be used as a vasoconstrictor in
the local anaesthetic solution.
Sharp needle blocksRetrobulbar block provided good akinesia and anaesthe-
sia, and was usually supplemented with a facial nerve block to paralyse orbicularis oculi. The principle of the technique was to deposit a small volume (2–3 ml) of anaesthetic solution in the muscle cone at the apex of the orbit using a 40 mm-long needle. Rare, but serious, complications occurred with these blocks, including retrobulbar haemorrhage, globe perforation, damage to the optic nerve or ophthalmic artery, and spread of the anaesthetic to the brainstem along the optic nerve dural sheath.6
Peribulbar block was introduced in 1986 to avoid the com-plications of retrobulbar block. A shorter needle places larger volumes of anaesthetic solution outside the muscle cone with the needle tip no further back than the equator. The anaesthetic spreads throughout the orbit and provides satisfactory operating conditions. The technique usually consists of two injections of local anaesthetic, one inferior and one medial to the globe. These sites are selected to avoid vital structures within the orbit. The volume used is usually enough to block the nerves to orbicularis oculi directly and avoid facial nerve block. Adaptations of the technique have been to direct the lateral injection up into the muscle cone just behind the globe. This produces a more rapid reliable onset of block with a smaller volume of anaesthetic solu-tion, and frequently the medial injection is dropped. This is the ‘modern retrobulbar’ technique.
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Any technique using a blindly placed sharp needle may result in serious sight-threatening complications, including globe per-foration. Sub-Tenon’s block is now commonly used for most surgery on the globe.
Sub-Tenon’s block: local anaesthesia is introduced to the sub-Tenon’s space through a single small incision in the inferona-sal quadrant of the eye.7 Posterior diffusion of the anaesthetic blocks sensation from the eye by direct action on the ciliary nerves as they pass through the sub-Tenon’s space. If a suitable volume of anaesthetic is used, complete akinesia is obtained as it diffuses into the muscle cone from the sub-Tenon’s space.8 This technique is commonly used for cataract surgery, with lower reported serious complications than for sharp needle techniques,9 but is also increasing in popularity for vitreo-retinal surgery.10
Technique of sub-Tenon’s block (Figures 1–4)• The patient lies supine with head on a pillow.• A few drops of topical anaesthetic are placed on the conjunctiva.• A few drops of 5% aqueous iodine are placed on the conjunctiva.• A small speculum is inserted to hold the eyelids apart.• The patient looks up and laterally.• The conjunctiva and Tenon’s capsule are pinched firmly with non-toothed forceps, 5–7 mm from the limbus in the inferonasal quadrant.• With round-ended spring scissors a small snip is made through both layers.• The closed scissor tips are passed through the hole, and the blades are opened while gently withdrawing them to form a short tunnel.• A blunt, curved 19G, 25 mm sub-Tenon’s cannula is passed into the sub-Tenon’s space and allowed to slide round the globe, over the sclera to a depth of 15–20 mm in the inferonasal quadrant.• The appropriate volume of local anaesthetic is slowly injected to minimize chemosis: 4 ml for cataract surgery, 5–6 ml for a trabeculectomy or corneal graft, and 8–10 ml for vitreo-retinal procedures.
Figure 1 Sub-Tenon’s block – pinch conjunctiva and Tenon’s with
• The cannula is withdrawn and slight pressure maintained over the closed eye for a few minutes when complete akinesia and anaesthesia are seen.• Sub-conjunctival haemorrhage is kept to a minimum by using topical epinephrine 1:10,000, avoiding cutting conjunctival ves-sels and extensive dissection, and using gentle, direct pressure.
Different cannulae can be used with similar effectiveness.11 Although safer for routine cataract surgery,12 sight-threatening complications can still occur with sub-Tenon’s block,13 and the anaesthetist must always be aware of the risks.
The local anaesthetic mixture: the characteristics of a block will depend on the anaesthetic solution used as well as the tech-nique. 2% lidocaine is effective within 5 minutes, and will give 30–40 minutes of surgical anaesthesia. 0.5% bupivacaine has a slower onset of action but longer duration of surgical anaesthesia (up to 4 hours) and is useful when postoperative analgesia is required. Ropivocaine has been used successfully in peribulbar blocks but has little advantage over bupivacaine in the small vol-umes needed in eye blocks.
Mixtures of lidocaine and bupivacaine are frequently used to provide rapid onset with delayed offset, but are of no practical advantage.
Addition of 1:200,000 epinephrine reduces haemorrhage in skin infiltration techniques but is not used in orbital blocks
Figure 2 Sub-Tenon’s block – snip through both layers.
Figure 3 Sub-Tenon’s block – form a tunnel with scissors.
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because the vasoconstriction may compromise retinal blood flow. The enzyme hyaluronidase in concentrations of 5–30 IU/ml enhances the spread of anaesthetic and speed of onset.
Patient managementDuring surgery the patient should be monitored with a pulse oximeter and ECG, and non-invasive blood pressure monitoring should be available if required. Trained staff should monitor the patient and the anaesthetist should be available for resuscitation or sedation.
Sedation: most patients readily tolerate ocular surgery under local anaesthesia with careful explanation, gentle handling and a sympathetic approach. Occasionally the very anxious patient may require sedation for cataract surgery. In vitreo-retinal sur-gery the patient may require sedation to enable them to tolerate the longer operating time. Various techniques may be used with appropriate monitoring; remembering that draping the head for surgery will reduce access to the airway. A small dose of intra-venous midazolam, 0.5–1.5 mg, before the anaesthetic, provides amnesia while avoiding over-sedation. ◆
ReFeReNceS
1 Local anaesthesia for intraocular surgery. The Royal College of
Anaesthetists and the Royal College of Ophthalmologists, 2001.
2 Friedman DS, Reeves SW, Bass EB, et al. Patient preferences for
anaesthesia management during cataract surgery. Br J Ophthalmol
2004; 88: 333–5.
3 Tan CS, Au Eong KG, Kumar CM. Visual experiences during cataract
surgery: what anaesthesia providers should know.
Eur J Anaesthesiol 2005; 22: 413–19.
4 Zafirakis P, Voudouri A, Rowe S, et al. Topical versus sub-Tenon’s
anaesthesia without sedation in cataract surgery. J Cataract Refract
Surg 2001; 27: 873–9.
5 Srinivasan S, Fern AI, Selvaraj S, Hasan S. Randomized double-
blind clinical trial comparing topical and sub-Tenon’s anaesthesia in
