Optic disk ovality as an index of tilt and its relationship to myopia and perimetry

Abstract

• Purpose: To examine the association of optic disk ovality with myopic refractive error, axial length, and the visual field. • Design: Prospective observational case series. • Methods: The study included 150 randomly recruited male subjects with myopia. In all cases, one eye was randomly selected, and subjective refraction, slit-lamp examination, applanation tonometry, gonioscopy, A-scan ultrasonography, funduscopy, and color optic disk stereo photography were performed. Disk ovality was assessed using the ratio of minimum to maximum disk diameter (index of tilt). A ratio of ≤ 0.8 was considered as significant disk tilt. Visual fields were tested using static automated threshold perimetry with two methods of optical correction: trial lenses and contact lenses. • Results: Of the total sample, 137 subjects completed the study. Mean age was 21.2 ± 1.1 year, and mean spherical equivalent was -6.36 ± 3.56 diopters. Mean ovality ratio was 0.83 ± 0.09; 55 subjects (40.2%) had significant tilted optic disks. Greater optic disk ovality (tilt) correlated with greater myopia (P = .009) and longer axial length (P = .009); 95.6% of subjects had normal visual fields with both methods of optical correction. Using multiple linear regression analysis, greater tilt was independently related to a higher mean defect on testing with trial lenses (P < .01). • Conclusions: Increased optic disk tilt was associated with higher myopia and reduced sensitivity on field testing. These factors are important in the assessment of glaucoma in patients with myopia. © 2005 by Elsevier Inc. All rights reserved.