Transition zone smoothness and its effects on postoperative corneal optics and epithelial thickness profile in myopic topography-guided surface ablation

Session Details

Session Title: Surface Photoablation/PRK

Session Date/Time: Tuesday 25/09/2018 | 14:00-16:00

Paper Time: 14:12

Venue: Room A3, Podium 2

First Author: : W.Zhou NORWAY

Co Author(s): :    A. Stojanovic                    

Abstract Details

Purpose:

To evaluate the influence of the transition zone smoothness on postoperative corneal optics and epithelial thickness profile in myopic topography-guided surface ablation, in order to identify optimal transition zone design for improved safety, efficacy, predictability, stability and quality of vision in treatment of myopia.

Setting:

Prospective contralateral study from Synslaser clinic in Tromsoe, Norway

Methods:

Eighteen volunteers with equal amount of myopia in contralateral eyes, underwent topography-guided surface ablation using different transition zone design for their two eyes. Transition zone that keeps low dioptric gradient, with optical zone decided by dynamic pupilometry, was used in eyes, assigned to group 1. Fixed transition zone, with diameter one mm larger than the optical zone, with optical zone decided by iterative process to achieve the maximum ablation depth matching the other eye’s, was used in eyes, assigned to group 2. Postoperative subjective refraction, visual acuity, higher-order-aberrations (HOAs) and epithelial thickness profile were compared between the two groups.

Results:

Ten months postoperatively, no statistically significant difference was detected between the two groups concerning corrected or uncorrected visual acuity, subjective refractive error, corneal curvature, or HOAs at 3.5mm zone. However, group 1 showed significantly lower even-order HOAs at 6.5mm zone (0.316µm and 0.346µm for group 1 and group 2, respectively. P=0.006), and less central epithelial thickening (12.9% and 15.8% thickened for group 1 and group 2, respectively. P=0.01. ). In addition, group 1 showed larger postoperative effective optical zone (EOZ) than group 2 (diameter of EOZ was 6.31mm and 5.91mm for group 1 and group 2, respectively. P<0.001).

Conclusions:

A smoother transition zone design in myopic surface ablation provides lower postoperative central epithelial thickening and lower even-order HOAs at 6.5 mm, as well as larger EOZ. It resulted in better quality of vision, while the predictability, safety and efficacy were the same. Stability will be evaluated one year postoperatively.

Financial Disclosure:

-