Purchase this article with an account.
Brian K. Armstrong, Beatriz Gomez, Jack Shao, Katie Hallahan, Ron Krueger, Abhijit S. Roy, William Dupps, Jr.; Ocular Response Analysis and LASIK Outcomes of Eyes with Myopia versus Myopic Astigmatism. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5783.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To evaluate differences in the biomechanical properties of myopic and myopic astigmatic eyes as measured with the Ocular Response Analyzer (ORA). We utilized both ORA standard variables and our own custom variables to look for differences between the groups. Differences in refractive error at 3 months following LASIK were also compared.
This retrospective study included 256 eyes that underwent LASIK for myopia (53 eyes, defined as ≤0.25D of astigmatism on preoperative manifest refraction) or myopic astigmatism (203 eyes, ≥0.5D of astigmatism). LASIK was performed with an IntraLASE femtosecond laser and the ALLEGRETTO WAVE® EYE-Q system. ORA, central corneal ultrasound pachymetry and topography were performed on all eyes preoperatively, and manifest refractions were compared before and 3 months after surgery. Student's t-tests and multivariate regression analysis were used to compare refractive outcomes and preoperative ORA variables in the spherical and astigmatic groups.
Preoperative spherical equivalent refraction (SE) in the myopia and myopic astigmatism groups were -4.19 D and -4.70 D, respectively (p = 0.06). In multivariate regression analysis of our groups, we found one custom ORA variable which was a significant predictor of the magnitude of the preoperative astigmatism (MinAOnsetRatio; p value = .005). At 3 months, the mean SE and residual corneal astigmatism were -0.21 D and 0.10 D, respectively, in the myopia group and -0.35 D and 0.20 D, respectively, in the myopic astigmatism group. The difference in mean SE at 3 months between the two groups was not statistically significant (p=0.1).
When comparing ORA variables for a myopic group compared to a group with myopic astigmatism, we found one custom variable that correlated with the degree of astigmatism with multivariate regression analysis. That variable takes into account how low the applanation signal falls when the cornea is concave and the length of time it takes for the cornea to reach that concavity. When comparing LASIK outcomes in SE between the two groups, we observed trends toward higher postoperative SE refractive error at 3 months for the myopic group.
This PDF is available to Subscribers Only