Normal age-related decay of retinal nerve fiber layer thickness

Purpose: To determine the normal age-related loss of retinal nerve fiber layer thickness (RNFLT) as measured on Stratus optical coherence tomography (OCT 3; Carl Zeiss Meditec, Dublin, CA) in an Asian Indian population. Design: Prospective, cross-sectional, observational study. Participants: One hundred eighty-seven eyes of 187 normal subjects (age range, 5-75 years) who satisfied the inclusion and exclusion criteria were included. The subjects were defined as normal if they had visual acuity of 20/30 or better, intraocular pressure less than 22 mmHg with normal optic disc, and no ocular abnormality. Methods: All patients underwent complete ophthalmic evaluation including imaging with Stratus OCT 3. Simple linear regression was performed to study the effect of age on RNFLT, with age as the independent variable and RNFLT as the dependent variable. Spearman's correlation was studied between the age and RNFLT. An analysis of variance was applied to compare RNFLT between the different age groups. The chi-square test also was used to evaluate the relationship between age and RNFLT. Main Outcome Measure: Effect of age on RNFLT. Results: One hundred eighty-seven eyes of 187 normal subjects were analyzed. Mean age standard deviation was 33.0 +/- 19.7 years (range, 5-75). Average RNFLT and RNFLT by quadrant demonstrated the tendency of RNFLT to decrease with increasing age, especially after age 50 years. Average RNFLT demonstrated a negative slope of 0.16 mu m/year (95% confidence interval [CI], -0.1 to -0.24). By quadrant, the superior average (negative slope, -0.23 [mu m/year; 95% CI, -0.1 to -0.34) showed a maximum tendency to decline with age, whereas in the inferior quadrant (negative slope, -0.08 mu m/year; 95% CI, 0.05 to -0.24), the age-related decay was minimal. Six clock-hour RNFLT had a least negative slope of -0.022 mu m/year (95% CI, -0.08 to -0.1). Chi-square test results showed a significant inverse relationship between age and average RNFLT (P 0.01). Conclusions: Age-related retinal nerve fiber layer (RNFL) loss is not uniform in all the quadrants, with maximum loss in the superior quadrant, and seems to reach a maximum after the age of 50 years. Furthermore, it seems that inferior quadrant RNFL is more resistant to loss.