Posters

Comparison of the predictability of refractive astigmatism correction by LASIK in eyes with low and high ocular residual astigmatism

Poster Details

First Author: T.Archer UK

Co Author(s):    D. Reinstein   D. Piñero   M. Gobbe   G. Carp     

Abstract Details

Purpose:

To compare the accuracy of the correction of manifest refractive astigmatism between eyes with low and high ocular residual astigmatism (ORA).

Setting:

London Vision Clinic, London, UK

Methods:

Retrospective analysis of myopic astigmatism LASIK procedures performed with the MEL80 excimer laser. The preoperative ORA was calculated using the Alpins method as the vector difference between the manifest refractive astigmatism (MRA) at the corneal plane and the Atlas corneal astigmatism (sim Ks). The outcome measure was the Index of Success (IOS); the ratio of preoperative MRA divided by postoperative MRA. Stage 1: low ORA defined as ORA/MRA<1, high ORA defined as ORA/R≥1. Stage 2: low ORA group reduced to only include eyes matched for MRA in the high ORA group. Stage 3: groups defined based on ORA magnitude with low ORA <0.50D, mid ORA ≥0.50D and <1.25D, and high ORA ≥1.25D. Stage 4: high ORA group subdivided into low (<0.75D) and high (≥0.75 D) corneal astigmatism (CA).

Results:

Stage 1: mean preoperative MRA was -1.31±0.62 D (-0.58 to -3.57 D) in the low ORA group (n=1753) and -0.81±0.22 D (-0.58 to -1.95 D) in the high ORA group (n=466). Mean IOS was 0.28 in the low ORA group and 0.40 in the high ORA group (p<0.001). Stage 2: mean IOS was 0.34 in the low ORA group and 0.40 in the high ORA group (p<0.001). Stage 3: mean preoperative MRA was -1.45±0.70 D (-0.59 to -3.57 D) in each group (n=189). Mean IOS was 0.28 in the low ORA group, 0.30 in the mid ORA group and 0.32 in the high ORA group (p<0.001). Stage 4: mean IOS was 0.24 in the high ORA/low CA group, and 0.35 in the high ORA/high CA group (p<0.001).

Conclusions:

Accuracy of refractive astigmatism correction was found to be worse in eyes with high ORA. However, matching for MRA treated and grouping by ORA magnitude reduced this difference to from 0.12 to 0.04 between the low and high ORA groups. The worst outcome was found in the group with high ORA and high corneal astigmatism. FINANCIAL INTEREST: One of more of the authors... receives consulting fees, retainer, or contract payments from a company producing, developing or supplying the product or procedure presented