ESCRS - PP22.01 - Effective Optical Zone And Its Impact On Astigmatism And Higher-Order Aberrations In Silk And Lasik

Effective Optical Zone And Its Impact On Astigmatism And Higher-Order Aberrations In Silk And Lasik

Published 2026 - 44th Congress of the ESCRS

Reference: PP22.01 | Type: Free paper | DOI: 10.82333/g4ns-zf05

Authors: Dr Rushad Shroff* 1 , Dr Apoorva Agrawal 1 , A/Prof. Ritu Arora 1

1Cornea and refractive,Shroff Eye Centre,New Delhi,India

Purpose

To determine the association between effective optical zone centration as well as its impact on visual outcomes, quality of vision and higher order aberrations (HOA’s) in Smooth Incision Lenticular Keratomileusis (SILK) and laser in situ keratomileusis (LASIK)

Setting

Tertiary eye care hospital in North India

Methods

Two hundred eyes of 100 patients treated with SILK (100 eyes) and LASIK (100 eyes) were included. The centration of the optical zone was evaluated on the tangential curvature difference map between the preoperative and 3-month postoperative scans using a superimposed set of concentric circles. The correlation between optical zone decentration and anterior keratometry values was evaluated. The effect of optical zone decentration on vector components of astigmatic correction and induction of higher-order aberrations (HOA) was assessed. Visual outcomes were also assessed

Results

The mean decentration distance was 0.21 ± 0.11 mm for SILK and 0.20 ± 0.09 mm for LASIK (p = 0.808). There was a significant correlation between anterior keratometric astigmatism and decentration distance (r = 0.7, p = 0.05) for SILK. Mean effective Optical zone was significantly larger(p=0.001) in the SILK group (5.35 + 0.22) than the LASIK group (4.88 +0.25). The total HOA’s and spherical aberration was lower in the SILK group though it did not show statistical significance. Significant correlation was demonstrated between the decentration distance and the induced total coma (SILK: r = 0.56, p = 0.04; LASIK: r = 0.59, p = 0.02). 95 % eyes attained a UDVA of 20/25 or better on day one. 90 % eyes were within 1 D of targeted correction

Conclusions

For the same planned optical zone, the effective optical zone after treatment was larger in SILK than in LASIK. There was lower induction of HOA’s and spherical aberration in the SILK group. Subclinical decentration was associated with the induction of total coma but it did not affect the lower-order astigmatic correction. Both procedures were found to be safe, accurate and effective for refractive correction