1. 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

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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 Jul;33(7):

9. 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

10. 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

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

12. 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

13. 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