epi LASEK: creating epithelial flaps using variable alcohol concentrations and variable duration of exposure Pravin K Vaddavalli, Subramaniam SV, Sangwan VS, Parulkar G, Vemuganti GK Cornea & Refractive surgery Service Pathology Service LV Prasad Eye Institute India The authors have no financial interests to disclose

Surgeon acceptability Introduction Surgeon acceptability Moderate skills Reproducible Stable Accurate Safe Reversible RK + ++ - ? LASIK/PRK +++ Phakic IOL Clear lens extraction INTACS Refractive surgery still has many drawbacks, chief among which is non reversibility Corneal implants like inlays and onlays can achieve this

Progressive loss of clarity with corneal inlays Introduction Barraquer 1960 Dohlman 1967 Choyce 1970 Beekhuis 1986 1 week Corneal implants 1 month 6 months 12 months 24 months Progressive loss of clarity with corneal inlays

Introduction Ideal position for a corneal implant is just beneath the basement membrane of the corneal epithelium Synthetic Onlay Epithelium Stroma Lens To achieve this we need to create a viable epithelial flap beneath which to place the onlay

Purpose Materials and methods To create a viable epithelial flap/pocket using a combination of alcohol and an epimicrokeratome Materials and methods 3 groups Group A: LASEK – alcohol assisted Group B: epi LASIK – epimicrokeratome Group C: epi LASEK – combination of alcohol exposure and epimicrokeratome

Materials and methods Group A: LASEK 5 patients undergoing PRK 20% isopropyl alcohol 20 sec exposure time Epithelial flap sent for histology Group B: epi LASIK 5 patients undergoing epi LASIK Moria epi K, Zyoptix XP epi or Norwood epimicrokeratome Epithelial flap sent for histology Alcohol Debridement of the Corneal Epithelium in PRK and LASEK: An Electron Microscopic Study AC Browning, S Shah, HS Dua, SV Maharajan, T Gray, MA Bragheeth. Invest Ophthalmol Vis Sci. 2003;44:510–513

Material and methods: epi LASEK: Group C 5 eyes undergoing PRK Pre treated with 20% or 10% isopropyl alcohol Treatment time 10 sec vs 5 sec Flap creation with Moria. Zyoptix XP or Norwood epimicrokeratome Epithelial flap sent for histology

Results: Group A: LASEK Periodic Acid Schiff 100 X showing irregular basement membrane and disrupted basal epithelial cells Literature also shows compromised epithelial cell viability * * Tanioka H, Hieda O, Kawasaki S, Nakai Y, Kinoshita S. Assessment of epithelial integrity and cell viability in epithelial flaps prepared with the epi-LASIK procedure. J Cataract Refract Surg. 2007 Jul;33(7):1195-200.

Results: epi LASIK: group B Intact Basal epithelial cell layer Disrupted Basal epithelial cell layer Basal epithelial cell layer – loose desquamating cells with vacuoles Moria epi microkeratome – Periodic Acid Schiff 100 X Norwood microkeratome – Periodic Acid Schiff 100 X

Moria epimicrokeratome with 20% isopropyl alcohol for 5 sec, PAS stain Basal cells not disrupted in most sections Moria epimicrokeratome with 10% isopropyl alcohol for 5 sec, PAS Intact basement membrane Norwood epimicrokeratome with 10% isopropyl alcohol for 10 sec, HE Basement membrane intact Scalloping of basal epithelial cell layer, ? artifactual Moria epimicrokeratome with 20% isopropyl alcohol for 5 sec, PAS stain Moria epimicrokeratome with 20% isopropyl alcohol for 5 sec, PAS stain Mostly regular cut Norwood epimicrokeratome with 10% isopropyl alcohol for 10 sec, PAS Regular basal cell layer with basement membrane

Results: Group C: epi LASEK Transmission Electron Microscopy 1000 X showing intact regular basement membrane

Results LASEK resulted in disruption of epithelial basal cells Epi LASIK resulted in cleavage through basal cells Epi LASEK resulted in most native morphology of basal cells 10% isopropyl alcohol for 5 sec pre treatment results in most regular epithelial flap

Conclusions epi LASEK may be the best way to retain epithelial viability First step to create viable epithelial flap for the placement of a corneal onlay Has applications in advanced surface ablation Can result in reduced post op pain, reduced haze Need to establish viability of epithelial cells by cell culture