ONE STEP BEYOND

Refractive Surgery Challenges and their most modern

approach

D. Alexopoulos MD,DO

www.lasereye.gr

Some of the most challenging refractive problems

Eccentric ablation Irregular, eccentric ,small optical zone after RK Hyperopia after myopic ablation Vision improvement in KCN

Τheir treatment has been attempted with variable success by the use of topography guided ablation, and in case of KCN with the addition of corneal cross linking (Topo Guided PRK ”Athens Protocol” –Kanellopoulos)

The reasons for the variable success of such treatments have been :

1. The inability to control the static and dynamic torsion of the eye

2. The lack of reliable and precise registration of the planed ablation on the cornea

3. The assumption of Pentacam of the corneal surface shape (best fit sphere –maps change with fitting)

4. The compensatory role of the corneal epithelium

We can now overcome the problems of imperfect registration of the ablation and be more precise at defining the corneal surface contour by using the Amaris (Schwind) platform in combination with Corneal Wavefront analysis

The Amaris uses a static & dynamic torsion control up to 12,5 degrees) and has a 6D eye tracker

Amaris eye tracker

Few reminders Registration of the ablation= matching the

desired corneal ablation on the corneal surface ( avoid eye torsion or decentration)

Corneal wavefront= Zernicke analysis of the corneal topography (higher order aberrations of the corneal surface)

Accelerated corneal crosslinking= Corneal collagen crosslinking by the use of high diffusion riboflavin formulations (Vibex Rapid) and high energy UV (30mW) for shortened periods of treatment (8min pulsed light)

Partial crosslinking = Crosslinking of the anterior corneal stroma as in accelerated crosslinking but less soaking time (90 sec) and less irradiation (75-90 sec at 30 mW)

Corneal wavefront Zernike analysis

Advantages of Corneal Wavefront maps

1. Show the cornea in terms of its optics2. Allow analysis of individual aberrations3. Allow simulations of vision, PSF, MTF4. Allow comparison with aberrometers

Amaris static cyclotorsion correctionDiagnosis

imageLaser image

Case 1: old RK with small ,decenterd OZBCDVA4/10 -4.00/-4.00 cyl

Corneal Wavefront of case 1

Corneal OCT of case 1

Treatment plan (ablation pattern) of Case 1Corneal Wavefront Guided Transepithelial PRK Xtra

(followed by accelerated partial crosslinking ) & MMC

Post op Case 1 BCDVA 9/10 -1.50 sph

Pre/Post op difference map Case 1

Case 1 Corneal OCT post op

CCL depth 190μ

Case 1 20 days post op

Case 2: Moderate KCN BCDVA 5/10 (can’t wear GP)

Case 2: Corneal Wavefront

Case 2 : Corneal OCT

Epi 52μ

Epi 60μ

Case 2: Treatment plan (ablation pattern)Corneal Wavefront Guided Partial transepithelial Prk

followed by full accelerated pulsed crosslinking & MMC

Case 2 Post op BCDVA 10/10-

Case 2 corneal OCT post op

Case 2 1 month post op

Case 3: Hyperopia after myopic PRK(cct 460 μ ) treated with thin flap (100μ) femto lasik & CCL

Xtra

Case 3 1 month post op

What was known

“regularly irregular” corneal surface could be treated with Topography or WF guided ablation

Topography guided ablation was based on Pentacam images and WF guided on total ocular WF measurements

Such WF guided treatments were not quantifiable ,HOA wise

The corneal epithelium was removed as in PRK or PTK The “Athens Protocol” by Dr. Kanelopoulos is based on

the above plus corneal crosslinking Post myopic PRK consecutive hyperopia was treated

with Hyperopic PRK (fear of ectasia)

What’s new The corneal wavefront guided ablation treats the

optical irregularities of the aberrated cornea It combines the meaningful and substantial WF guided

ablation but focused solely on the corneal surface contribution (as the topo guided ablation)

This must be coupled with a precise ablation registration (with torsion control) and a fast and reliable eye tracker

Transepithelial PRK makes use of the “smoothing” effect of the corneal epithelium

Accelerated ,partial or full crosslinking, effectively “strengthens “ the cornea after such treatments

The use of Femto thin flap Lasik combined with partial crosslinking (Xtra) can be safely used in treating consecutive hyperopia after myopic PRK

What I would like for Christmas!

New topograph

er!Cassini???