Refractive Surgery Challenges and their most modern approach D. Alexopoulos MD,DO

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

 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)

Advantages of Corneal Wavefront maps 1. Show the cornea in terms of its optics 2. Allow analysis of individual aberrations 3. Allow simulations of vision, PSF, MTF 4. Allow comparison with aberrometers

Diagnosis image Laser image

CCL depth 190μ

Epi 52μ Epi 60μ

 “ 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)

 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

New topographer! Cassini???