Axial Length and Optic Disc Size in Normal Eyes

Abstract

Abstract: : Purpose: To examine the relationship between optic disc parameters and axial length among normal subjects. Methods: Normal subjects were enrolled in this prospective study. All patients underwent a complete eye exam including automated achromatic perimetry, pachymetry, biometry and scanning laser ophthalmoscopy (HRT II). Topographic parameters and axial length were compared between African–American and Caucasian subjects. Results: 239 eyes (239 subjects) were studied. Mean age was 42.9±12.6 years, mean central corneal thickness (CCT) was 540±34.6 µm, and mean axial length was 23.63±0.9 mm. African–American subjects (n=136) had larger disc and cup areas (P=0.015 and P=0.02 (T–test), respectively), greater cup–to–disc area ratio (P<0.0001), greater cup volume (P=0.05), greater mean and maximum cup depth (P=0.01 and P=0.003, respectively), greater horizontal cup–to–disc ratio (P=0.002), and greater linear cup–to–disc ratio (P=0.02), than Caucasian subjects (n=103). Optic disc and cup areas increased with axial length (r=0.21, P=0.01, and r=0.22, P=0.008, respectively (Pearson correlation coefficient )) in African–Americans but not in Caucasians (P=0.07 and P=0.57, respectively). Conclusions: Normal subjects of African ancestry have larger discs, and larger and deeper cups than Caucasians. Disc area increases with axial length in black but not in white patients.

Keywords: optic disc • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)