Correlation of visual acuity and ocular pigmentation with the 16-bp duplication in the HPS-1 gene of Hermansky-Pudlak syndrome, a form of albinism

Abstract

Objective Patients with the Hermansky-Pudlak syndrome (HPS), a form of albinism, were studied. The first purpose of this investigation was to determine if visual acuity was related to the presence or absence of the 16-bp duplication in the HPS-1 gene. The second was to study the correlation between the degree of ocular pigmentation and visual acuity within the two genetic groups described above. Design Cross-sectional study of a series of consecutive patients. Participants Forty-nine patients with HPS with or without the 16-bp duplication in HPS-1. Methods Best corrected visual acuity (VA) using Early Treatment Diabetic Retinopathy Study (ETDRS) charts, photographic gradings of iris transillumination and of visibility of choroidal vessels in the macula (macular transparency). Main outcome measures Association between VA and the presence or absence of the 16-bp duplication in HPS-1 and correlation between VA and the degree of iris transillumination (iris score) and macular transparency (fundus score), as determined by masked reading of photographs, with respect to the presence or absence of the 16-bp duplication in HPS-1 were the main outcome measures. Results The VA of the better eye did not differ between the two genetic groups ( P = 0.322, two-sided t test). Spearman’s rank correlation between VA and iris scores in 39 eyes of 20 patients with the duplication was not statistically significant ( P = 0.698) but was statistically significant in 36 eyes of 19 patients without the duplication ( P < 0.001). Among all patients, the correlation was statistically significant ( r = −0.36 in RE and r = −0.51 in LE). Spearman’s rank correlation between VA and fundus scores in 36 eyes of 19 patients with and 34 eyes in 18 patients with and without the duplication was statistically significant ( P = 0.035 and P = 0.008, respectively). Among all patients, it was also statistically significant ( r = −0.39 in RE and r = −0.45 in LE). Conclusions The mean VA of the better eye did not differ in patients with the 16-bp duplication compared with those without the duplication. There were statistically significant associations between VA and the iris score and the fundus score except for the VA and iris scores in patients with the 16-bp duplication. However, because of the variability of VA, these associations were not large enough for useful prediction of VA based on the degree of ocular pigmentation.