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Higher order and spherical aberrations of anterior cornea surface before and after LASIK

¹ Ophthalmology, Refractive surgery center, San Diego, CA
² Ophthalmology, Refractive surgery center,Navy Medical Center, San Diego, CA
³ Ophthalmology, Navy Medical Center, San Diego, CA
⁴ Ophthalmology, Navy Medical Center,Refractive surgery center, San Diego, CA

Commercial Relationships: S. Xu, None; S. Schallhorn, None; J. Laurent, None; A. Engle, None.

Grant Identification: none

Abstract

Purpose: To investigate the higher–order (HO) and the spherical aberrations(SA) of the anterior cornea in normal myopic eyes before and after LASIK surgery.

Methods: Using the VOL–Pro program, corneal pupil zone HO rms and the Zernike coefficient of the SA ( Z₄⁰) before and after LASIK surgery were computed from the corneal Orbscan topographic maps of 108 myopic eyes (54 subjects). Subjects were 13 female and 41 male; mean age 35.4 ± 7.23; pupil sizes ranged from 4 to 8mm. Mean manifest preoperative spherical equivalent was –4.11±1.51 D (ranged –1.5D to –8.25D). Correlations between the aberrations and pupil size, manifest spherical equivalent (SE), uncorrected visual acuity (UCVA), best–corrected visual acuity (BCVA) and the subject’s responses to psycometric questionnaires were analyzed using Statistica 6.0.

Results: Post LASIK, the HO rms and the coefficient of the SA were increased in 88.0% (95/108) and 96.3% (104/108) of eyes, respectively. The Mean HO rms was 0.50 ± 0.5297µm preoperatively and 0.71± 0.3839µm postoperatively (P<0.001). The mean coefficient of the SA was 0.26 ± 0.1505µm preoperatively and 0.51± 0.3085µm postoperatively (P<0.0001). P value of the correlation between pre– and post–HO rms and SAs and pupil size, manifest SE and VA are listed:

Pupil size Pre–SE Post–SE UCVA BCVA Pre–HO rms <0.001 =0.7447 =0.9563 =0.4714 Pre–SA <0.001 =0.1121 =0.8835 =0.1818 Post–HO rms <0.001 =0.0008 =0.0066 =0.1197 =0.5679 Post–SA <0.001 =0.00001 =0.0116 =0.1845 =0.5445

The preoperative SA was correlated with subject’s symptoms of glare and clarity, postoperative SAs correlated with haze, postoperative HO rms correlated with symptoms of glare and haze (P<0.05).

Conclusion: Anterior corneal HO rms and SA varied greatly among subjects and increased post LASIK which correlated with the pupil size and the degree of myopia. Higher order and spherical aberrations do not appear to affect the high contrast central visual acuity but do appear to affect the quality of vision.

Keywords: refractive surgery: corneal topography • refractive surgery: LASIK

© 2004, The Association for Research in Vision and Ophthalmology, Inc., all rights reserved. For permission to reproduce any part of this abstract, contact the ARVO Office at arvo{at}arvo.org.