Optic Disk Asymmetry in a Spanish Normal Population: The Segovia Study

Abstract

Abstract: : Purpose: Describe the prevalence and characteristics of optic nerve asymmetry in a Spanish normal population. Methods: Population-based and cross-sectional study. Subjects were randomly selected by gender and age groups from the population over 40 years living in the city of Segovia (Spain). Three hundred and forty six normal subjects were included in the study. All had VA ≷ 20/40, IOP < 22 mmHg, open angle and, normal and reliable visual fields (Humphrey Visual Field Analyser) in both eyes. Stereoscopic optic-disk photographs were obtained and evaluated by two independent observers. In case of disagreement between the two observers, a third experienced glaucoma specialist evaluated the photographs. Prevalence of asymmetry was calculated in the sample and estimated in the population. Characteristics of optic nerve head asymmetry were described. Results: Mean (SD) vertical and horizontal cup/disk ratio in the sample was 0.06 (0.06) and 0.05 (0.06) respectively. The following table shows the prevalence of cup/disk ratio asymmetry.  

Table: Number of cases (%) with a certain value of cup/disk ratio asymmetry. Conclusion: Moderate asymmetry is frequently found in normal eyes. This results are similar to those found in epidemiological studies performed in other countries.

Keywords: 498 optic disc • 430 imaging/image analysis: clinical