Early detection of keratoconus by higher order abberations

ABSTRACT

Keratoconus is a bilateral, non-inflammatory and progredient corneal ectasia. It is a progressive disease ultimately affecting both eyes, although only one eye may be affected initially. The Aim of This Study is to detect subclinical keratoconus in patients whose fellow eyes are diagnosed with early keratoconus using corneal higher order aberrations. This prospective observational comparative study comprised 72 eyes of 36 individuals that were divided into three groups, normal eyes as control[group A] and eyes with recently diagnosed cases with keratoconus [group B] and fellow clinically free eyes of those patients [group C]. Wavefront analysis for each cornea was performed; Root Mean Square [RMS] of anterior corneal higher order aberrations and separate types of cornea! higher order aberrations using Zernike Polynomials were analyzed. Spherical aberration in group A was 0.206 [+ .074] and in group C-0.17 [+ .737] and a mean difference of-0.376 and p value of 0.01. Coma aberration in group A was 0.233 [+ .146] and in group C-2.33 [+ .903] and a mean difference of 2.097 and p value of 0.00. While RMS of higher order aberration in group A was 0.373 [+ .124] and in group C 2.69 [+ .930] and a mean difference of 2.325 and p value of 0.00. Also comparison of group A [normal patients] and group B [keratoconus suspect patients] revealed statistically non significant difference in spherical aberrations and highly statistically significant difference in coma, and RMS of higher order aberrations values. Anterior corneal surface higher order aberrations [coma aberrations and RMS of HOAs] are significantly higher in eyes with keratoconus than in normal eyes. While the Spherical aberrations are significantly lower than in normal individuals