Phototherapeutic keratectomy By Dr. Safaa Refaat

PTK By Dr. Safaa Refaat 11


PHOTOTHERAPEUTIC KERATECTOMYPHOTOTHERAPEUTIC KERATECTOMYFORFOR

SUPERFICIAL CORNEAL OPACITIESSUPERFICIAL CORNEAL OPACITIES

ByDr. Safaa Refaat

FRCSG , MSc, MBBS

INTRODUCTION


Over the years, many surgical procedures have been

established to restore the corneal clarity & regularity, or to

replace the opacified cornea.


Excimer Laser

The term “excimer” “excited dimer”First described by Houtermans in 1969.In 1976 commercially introduced.In 19851st excimer laser Corneal Photoablation by Seiler.In 19881st PRK by Mc Donald et al.


Excimer Lasers Emissions

Gas Medium Wave Length (nm)

F2 157 nm

Xe2 170 nm

ArF 193 nm

KrCl 222 nm

KrF 248 nm

XeCl 308 nm

XeF 351 nm


Ablative photodecomposition

breaking intra molecular bonds molecular fragmentsGas plum

condensation

pseudomembrane.

Mechanism of action:


The ArF excimer laser ablate the corneal tissue with:

extreme precision

minimal adjacent tissue damage.


PHOTOTHERAPEUTIC KERATECTOMY

DEFINITION:

The use of the excimer laser in treatment of corneal pathology is termed PTK as opposed to PRK.


Indications The best results of PTK are obtained when pathology is limited to the anterior one fifth.

Patients with deeper corneal scars may also benefit from PTK.

The corneal thickness after PTK should be < 250 μm.


There are four distinct PTK treatment groups:

1- REE & painful BK.

2- Surface irregularities.

3- Corneal opacities.

4- Complications of PRK and LASIK.

1-


1- Recurrent Corneal erosionsPainful REE syndrome abnormalities in the Ep.-BM complex.

The aim of PTK

Removal of enough part of Bowman`s layer.


· Painful bullous keratopathy

PTK is effective in the management BK

bullae are resolved

pain is abolished.


Due to:Degenerations Salzmann’s nodules

Band keratopathy.

2- Irregular surface


Granular dystrophy

Lattice dystrophy.

With Anterior Corneal Dystrophies


keratoconus

Reis-Buckler’s dystrophy.

Irregular astigmatism after refractive surgery.


3- Corneal opacitiesCorneal dystrophies

Map dot finger print D.

Reis-Bückler’s D.


Schnyder’s crystallinedystrophy.

Avellino Latticedystrophy.


Granular Dystrophy.

Fuch’s dystrophy: Subepithelial scarring

Reduce the stromal bulk edema.


Macular Dystrophy.

Herpetic scars.


Surgical scars ex. Pterygium excision.

Recurrence of dystrophic changes after PKP.


4- Treatment of PRK and LASIK complications

A-Central Islands: 6 months after PRK 2 months after LASIK

B-Corneal Haze after PRK

Wait 6 to 12 months.


C – Decentered Ablations: If >1mm symptomatic. PTK can be effective.

D – LASIK flap complications: Irregular astigmatism

loss of BCVA. PTK to restore regular

corneal surface.


Other indications

Superficial infectious keratitis resistant to medical treatment

”controversial”

Corneo- conjunctival carcinoma:Spadea et al.(2002); reported the

successful use of PTK in the treatment of a case with recurrent intraepithelial corneo-conjunctival carcinoma.


ContraindicationsContraindications

Systemic Ocular

Generalized deblitating diseases

Ocular surface diorder&infections

Auto immune disease

Uncontrolled DM.

Uveitis, glaucoma

Significant corneal thining or Neovascularization.


Patient Qualification For PTK

Dume et al divided the patients qualified for PTK into three groups :Best patients for PTK

lesions in anterior 100μm. Ideal patients elevated

scars homogenous lesion within the ant. 100μm.


Patients considered acceptable but not ideal minimal tissue loss

or both elevated & superficial scarring.Patients considered unacceptable

deep scars or with significant loss

tissue.


Surgical techniques1. Epithelial debridement:

An ideal method for epithelial debridement will be: Rapid to prevent dehydration. Would leave a clean and smooth

epithelial defects. Reproducible.


Variable techniques :Mechanical debridment.Laser trans-epithelial ablation.High speed rotating brushes.Diluted ethanol.

OR, Various combinations : laser scrape methods.ethanol- assisted mechanical debridement.


smoothing of the anterior corneal

surface:It is of particular importance Excimer laser will reproduce surface irregularities deeper within the stroma.


Masking techniquesMasking fluid of inadequate viscosity irregular ablation surface.


Masking fluid of high viscosity irregular ablation surface.


Masking fluid of adequate viscosity regular ablation surface.


There are many types of masking agents.

Modified collagen gel modulators are of the most recent &ideal

masking agents ex. the BioMask & PALM gel


The PALM Technique.


The technique and depth indication and the aim of ttt.

PTK in REE:Epithelium debridement.

Large spot size such as 6.5 mm.

Depth 8 -10 μm.

2- Stromal ablation:


Bullous keratopathy:

Moderately deep ablation: pain neural plexus. the swelling quantity of MPS

osmotic load. Scarring epithelial stability.


corneal opacities or dystrophiesRemove only the visually significant opacities.

Debridement of elevated opacities as Salzman`s nodules & calcium deposits.

Ablation graded until we reach target corneal clarity.


Complications and side effects

1. Post operative pain.

2. Delayed re-epithelialization

3. Corneal infiltrates

4. Stromal haze

5. Glare and halos

6. Hyperopic shift


Corneal infiltratesA-Sterile corneal infiltrates

B-Microbial & Immunological

Keratitis.

C-Reactivation of herpes

simplex keratitis.


Stromal haze

Activated keratocytes new collagen and proteoglycan matrix haze formation


Grading of corneal haze:Grade 0 Totally clear cornea.

Grade0.5 Barely perceptible haze, (seen only against the red reflex).Grade 1 Trace haze (of minimal density seen with direct and diffuse illumination).

Grade 2 Mild haze, (easily visible with direct focal slit illumination).

Grade 3 Moderate haze, (partially obscures iris details).

Grade 4 Severe haze, (that completely obscures iris details).


Visual disorders of night glare and halos

Optical zone must be greater than the pupil

to avoid foveal & para foveal glare or ghosting


Hyperopic shift:

It is one of the most commonly seen side effect.

Measures to reduce the hyperopic shift: Shallow ablations.Transition zone settings. Skillful use of masking agents.


Other Complications

• Corneal graft rejection.• Keratectasia.• Limbal stem cell deficiency. • Elevation of the intraocular pressure .• Cataract. • Rare reported complications:

Ptosis Intracorneal granulomatous inflammation .



Aim Of The WorkTo evaluate the safety

and efficacy of PTK in improving vision in patients with poor

functional visual acuity due to superficial corneal opacities.


Materials

We performed a non-randomized prospective clinical study on 10 eyes of 10 patients with defective vision due to central or para central superficial corneal opacities.


Inclusion criteria

Superficial corneal scars or opacities limited to the anterior one third of the stroma.


Our cases included:corneal scars (7 cases).Reis-Buckler`s (one case)Granular (one case). Salzmann’s Nod.(one case).

PRE-OPERATIVE INDICATIONS

scar

Graneular DystrophyRies-

Buckler's

salezman nod.deg.


Exclusion criteria Ocular exclusion criteria included:Ocular surface disorders & infection.Uveitis .Corneal neovascularization. Recently active Herpetic scars. Corneal thinning.Glaucoma or suspected glaucoma.


Systemic exclusion criteria included:

Generalized debilitating diseasesAutoimmune diseases.Uncontrolled DM.Collagen vascular diseases .Pregnant and lactating women .


Pre operative preparations History. Examination :Unaided and BCVA..Refraction. Pupillary light reflex, and pupil size Fluorescine BUT. Corneal pathology. IOP, Dilated fundus examination Ultrasound pachmetry


The Main Preoperative Data.


Pre-operative medication:

Prophylactic antibiotic(Ciprofloxacin ED) two days before the procedure.

Mild pre operative Sedation.


Technique

Technolas 117, 193 nm excimer laser system.Fluence setting used was 160mJ/cm2

Pulse frequency of 50 Hz.


Surgical Steps:Topical aneasthesia.Mechanical epithelial debridment.Setting of the ablation depth and diameter..Stromal ablation. Irrigation with BSS.Soft C.L.


A 47 yrs. old female with para central corneal scar.


Case with Salzmann’s nodules. preoperative BCVA 6/36. postoperative BCVA 6/6.


Aphakic patient with central superficial corneal opacity.


The Main Operative Data


Post operative care

Strong pain killer.

Tobramycin with 0.1%dexamethazone combination eye drops .

Preservative free artificial tears.

When the epithelial healing was complete flurometholone 0.1% for 2-4 months.


Postoperative examination:

Epithelial healing.BCVA. Refraction.Symptoms corneal light scattering. Anterior stromal haze.



Results:Epithelial healing: Complete in 72hours

Visual outcome: All eyes showed improved BCVA except one.The improvement in BCVA was statistically

highly significant (P< 0.001 ) (P =0.00647) The mean preop. BCVA was 6/24 (+/- 2 lines). The mean postop. BCVA is 6/12 (+/- one line).


GAINED SNELLEN’S LINES GAINED S. LINES

no lines

1 line

2 lines

3 lines

4 lines

5 lines



Refractive out comes Two eyes showed a myopic shift.

one eye showed no change in SE.

7 eyes showed a hyperopic shift.

Change in SE statistically insignificant. (P =0.22).

The mean preoperative SE was –0.3750 D(+/-3.1) The mean postoperative SE was+1.075 D(+/-1.8)

The mean change in SE was +1.45 D (+/- 2.16)


CHANGE IN REFRACTION.


One eye with combined PTK and PRK developed postoperative astigmatism -5.75D compared to – 3.75D preoperative.

Symptomatic outcome

All patients experienced improvement in their quality of vision and decreased symptoms of eye fatigue and irritation.


CHANGE IN SE


Discussion

Compared to lamellar and PKP, excimer laser PTK is the:Safest & Least aggressive Faster visual recovery.Lower incidence of astigmatism. Could be repeatedLower cost.


Szentmáry et al (2004) found that PTK does not appear to impair the outcome of subsequent PKP.

Koreishi et al (2003) in a comparative study bet. primary treatment of lattice dystrophy with PTK versus PKP, they found that PTK alone give equal or better V.A.


Stewart et al (2002) had found that 93% of PTK treated cases with corneal dystrophies maintained or improved their BCVA. All were free of symptoms of REETrend towards a hyperopic shift. % 17 showed recurrence of the dystrophy.


Dorgu et al (2000) reported the findings of 14 PTK for mid stromal corneal scars:

They noticed that corneal sensitivity, tear film BUT & tear film lipid layer interferometry grades improved gradually and significantly after PTK.


In our work, we aimed to study visual and symptomatic outcome of PTK in 10 eyes with superficial corneal opacities.

We attained visual improvement in 9 eyes (90%) and saw that PTK could obviate the need for PKP.

THERE WERE NO SERIOUS COMPLICATION .


One patient with combined PTK and PRK no change in the BCVA. Our experience from this case will not encourage combined refractive correction with primary PTK. This could be due to:Unreliable refractionScar induced astigmatismDifferential ablation rate.


Conclusion:PTK improves both quality and quantity of vision.PTK can alleviate the need for PKP. The recent advances in PTK techniques:New, ideal modulators. Real time corneal topography feedback.Wave front analysis.

Will allow for reshaping every corneal surface to achieve the optimal corneal contour.


THANK YOUTHANK YOU

Date post:	16-Jul-2015
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Phototherapeutic keratectomy By Dr. Safaa Refaat

Science