| Summary: | Purpose: To compare topographic indices and anterior corneal higher order aberrations (HOAs) of forme fruste keratoconus (KC) (fellow eyes) with clinical KC and control eyes. Setting: Tertiary Eye Hospital, India. Materials and Methods: This study retrospectively reviewed 298 patients with KC. Patients were evaluated with placido-based topographer. KC was diagnosed according to Rabinowitz and McDonnell criteria and clinical sign. Twenty-one patients with clinical KC in one eye (Group A), fellow eye (Group B) with normal topography with no clinical sign, and 21 control eyes (Group C) were included in the study. Topographic indices (keratometry, inferior superior ratio, irregularity, shape factor, and eccentricity) and HOAs (trefoil, coma, spherical aberration, total root mean square [RMS], HOAs RMS of third to seventh order for 6 mm diameter) were obtained. Group B was compared with Groups A and C. Results: The prevalence of an extreme asymmetry of KC in our study population is 7.04% with mean age of 21.98 ± 7.39 years. All topographic indices were higher in Group A compared to Group B (P < 0.01) and no significant difference was found between Groups B and C. All HOAs were higher in Group A compared to Group B (P < 0.05). HOAs RMS, oblique trefoil and spherical aberration were significantly higher in Group B compared to Group C (P < 0.02). Of these 21 patients, four had severe to advanced KC in one eye. Conclusions: Corneal HOAs changes are first to appear in fellow eyes of unilateral KC, which may makes them useful tool in monitoring progression and early detection of KC changes in fellow eyes.
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