Title: Changes in Posterior Corneal Curvature, Asphericity and Longitudinal Spherical Aberrations Following Myopic Laser in Situ Keratomileusis (LASIK)
Authors: Dr Ashok H. Madan, Dr Madhura Chandratreya, Dr Kavita Dhabarde
DOI: https://dx.doi.org/10.18535/jmscr/v6i11.112
Abstract
Purpose: To assess the changes in the posterior corneal curvature, asphericity and longitudinal spherical aberrations after myopic laser in situ keratomileusis (LASIK)
Method: Prospective nonrandomized comparative study. 68 eyes of 16 women and 18 men were included, with mean age at the time of surgery of 24.79 +3.47 (range 20-35) years ,with a spherical equivalent(SEQ) of -1.5 to -11.75 (mean ,-5.00 +2.168). All procedures were accomplished with the Star S4 IR excimer laser and the Moria microkeratome. (Flap size 90/130 microns). The residual stromal bed thickness of > 250 um or >50% of original thickness of the cornea was maintained. Subjective refractometry, corneal topographical analysis and pachymetry with Sirius (placido disc topography with Scheimpflug tomography) were performed before and 3 months after LASIK for myopia (n=12, range -1.5 D to -5.12 D, mean - 3.20+2.10 D ) and myopic astigmatism (n=56, sphere -1.5 to-10.75 D, mean -4.78 + 2.13 D, cylinder -0.25 D to-3.5D, mean -1.07 + 0.78D).
Results: Paired‘t’ test was used for analysis. A P value < 0.05 was considered to be statistically significant. Overall, change of posterior corneal curvature (-6.259+0.18D/-6.27+0.21 D, P=0.10) was not statistically significant. Change of asphericity (0.89+0.25/1.03+0.12, P <0.001) was highly significant. Change in longitudinal spherical aberrations (0.45+0.33/0.61+0.83, P=0.16) was not found to be significant.
Conclusion: No significant change is seen in the Posterior corneal power/ Longitudinal spherical aberrations following LASIK, but change in asphericity of the cornea (from prolate to oblate) is significant.
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