Unique nomogram findings for SMILE: primary astigmatism correction and LASIK retreatment

Session Details

Session Title: Small Lenticule Extraction

Session Date/Time: Tuesday 25/09/2018 | 08:00-10:30

Paper Time: 09:36

Venue: Room A3, Podium 3

First Author: : T.Archer UK

Co Author(s): :    D. Reinstein   G. Carp   R. Vida              

Abstract Details

Purpose:

To report unique nomogram findings for primary myopic astigmatic SMILE and retreatment by LASIK.

Setting:

London Vision Clinic, London, UK

Methods:

Retrospective review of cylinder correction in primary SMILE and retreatment by LASIK at London Vision Clinic. Vector analysis was performed for the primary SMILE population to evaluate the accuracy of refractive astigmatism correction. The analysis was repeated for groups according to the axis of astigmatism (positive cylinder notation): WTR (60˚-120˚), oblique (30˚-60˚ and 120˚-150˚), and ATR (0˚-30˚ and 150˚-180˚). Retreatment by LASIK was performed using our multivariate nomogram for LASIK retreatments, including sphere, cylinder, age, and primary SEQ as variables. Linear regression analysis between laser SEQ and achieved SEQ was performed to derive a nomogram.

Results:

Mean refractive cylinder was 1.29±0.62 D (range: 0.75 to 4.25 D). Mean Difference Vector magnitude was 0.37 D. Mean angle of error was 0.28±8.19˚ with >15˚ in 6%. TIA vs SIA slope was 1.07 for the WTR group, 1.15 for the oblique group, and 1.32 for the ATR group. Mean attempted SEQ for retreatment by LASIK was -0.04±0.99D (-1.88 to +1.50D). Mean postop SEQ relative to the target was +0.19±0.46D (-0.88 to +2.13D), with 81% within ±0.50D. The linear regression equation for consecutive myopic treatments was 1.21 * laser SEQ + 0.05, indicating an overcorrection.

Conclusions:

This study found the need for an axially dependent nomogram for cylinder with the nomogram regression line slope calculated according to the cylinder axis. In LASIK over SMILE retreatment, it was found that consecutive myopic retreatment requires a different nomogram to consecutive myopia retreatment by flap lift after primary LASIK.

Financial Disclosure:

... receives consulting fees, retainer, or contract payments from a company producing, developing or supplying the product or procedure presented, ... travel has been funded, fully or partially, by a company producing, developing or supplying the product or procedure presented