Visual Function and Central Retinal Structure in Choroideremia

PURPOSE. To define the clinical phenotype of a cohort of patients affected with choroideremia. METHODS. A retrospective study of patients with choroideremia included two centers. Data collected included age, visual acuity, refractive error, color vision, kinetic perimetry, optical coherence tomography (OCT), and genotype information. RESULTS. Sixty male participants were recruited. Genotype information was available for 58 cases, and nonsense mutations were most commonly observed. Eight novel mutations were identified including a missense mutation. The mean age at the first visit was 30.1 years (range, 5-65 years) and thirty-seven patients (61%) had more than one visit with a mean follow-up period of 10.3 years (range, 1-23 years). Visual acuity was not associated with age for patients younger than 30 years (P = 0.46) but significantly associated with age for the age group above 30 years (P < 0.0001). Central retinal thickness was significantly associated with visual acuity (P = 0.03) and with age (P = 0.0014). The extent of visual field documented by kinetic perimetry showed a negative correlation with age to tested stimuli; the smallest target used (I-4e) showed the earliest and most rapid deterioration below the age of 20 years (P = 0.0032). Color vision was abnormal in 46.7% of cases (mean age, 36.3 years; range, 18-61 years), which was associated with older age (P = 0.0039). Central OCT images were abnormal in all cases, as early as age 10 years. Outer retinal tubulations were observed in all but five patients. No genotype-phenotype correlation was observed. CONCLUSIONS. This comprehensive structural and functional characterization of a large cohort of patients with molecularly confirmed choroideremia indicates that certain parameters are not changing significantly with time while others are. The latter warrants a prospective natural history study, ultimately to be considered as outcome measures for interventional clinical trials.