Abstract
An excimer laser (VISX Twenty/Twenty Excimer Refractive System) was used to treat 51 eyes for myopia and astigmatism. Uncorrected pretreatment visual acuity was between 6/18 and 6/60 (log unit +0.45 to +1.0) in 59% and worse than 6/60 in 29%. The mean pretreatment spherical refractive error was –4.05 dioptre (range 1.25 to 13.25), and the mean pretreatment cylindrical error was –0.97 dioptre (range 0.25 to 4.00).
Results
Uncorrected visual acuity measured 6/6 or better (log unit 0.0 or less) in 80% at three months, and averaged 6/6 for all eyes at six months post-treatment, with 75% eyes obtaining 6/6 or better. The mean post-treatment spherical error decayed according to pretreatment values, with a mean sphere of –0.20 dioptre for eyes initially less than –2.00 dioptre, –0.40 dioptre (for those between –2.25 and –3.00), –0.71 dioptre (for those between –4.25 and –5.00), and –1.15 dioptre for eyes initially above –6.25 dioptre. Vectored cylindrical correction exhibited response proportional to initial refraction, with a mean post-treatment cylinder of –1.83 dioptre for eyes formerly averaging –3.08 dioptre, –0.55 dioptre (eyes initially averaging –1.63 dioptre), and –0.51 dioptre (eyes initially averaging –0.67 dioptre). Vector analysis of post-treatment astigmatism showed 58% eyes exhibiting 51 or more degrees of axis shift, although 34% eyes remained within 20 degrees of their pretreatment axis.
Conclusions
An effective reduction in spherocylindrical error was achieved with all eyes, although axis misalignment was a common event.
Get full access to this article
View all access options for this article.