Choroideremia: Effect of age on visual acuity in patients and female carriers

Abstract

Background/aims: The extent and time course of vision loss in Choroideremia (CHM) is still unclear. We undertook this study to quantitate the change in visual acuity (VA) over time in order to gain a better understanding of the natural course of this retinal disorder.Methods: Corrected VA of 120 males with CHM and 53 female carriers were collected from 24 studies and/or case reports published between 1981 and 2010, as well as from data on 15 patients examined at the Cole Eye Institute (Cleveland Clinic). Cross-sectional and longitudinal analyses were used to investigate the relationship between VA and age, as well as the progression rate of VA with age, respectively. Age grouping effects were investigated using ANOVA.Results: The mean age of affected males was 36.6 ± 17.7 years. The mean logMAR VA was 0.35 ± 0.53. There was a significant 0.0072 decrease in logMAR VA per year (p = 1.22 × 10-4). There was a significant difference between VA of patients <50 years of age and those >50 years (0.27 ± 0.39 vs. 0.61 ± 0.81, p = 2.90 × 10-5). When we compared the rate of VA loss for patients <50 years vs. those >50 years, we also found a significant difference (0.01 ± 0.04 vs. 0.06 ± 0.08, p = 1.23 × 10-2). The average age of female carriers was 36.4 ± 17.7 years, with an average logMAR VA of 0.36 ± 0.6. There was no significant correlation between VA of female carriers and age (p = 0.12) with 46% of female carriers having a VA better than 20/20 at an average age of 33 years compared to 25% of affected males at 30 years.Conclusion: In affected males with CHM, VA decreases very slowly until subjects reach 50 years of age, at which time the rate and extent of vision loss become significantly higher. Additionally, VA decreases more rapidly as individuals get older. In contradistinction to affected males, VA loss in female carriers is much milder.