Visual Function and Central Retinal Structure in Choroideremia

Abstract

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.