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Abstract
PURPOSE: The authors investigated central retinal function in albinism by measuring incremental light detection thresholds in a group of oculocutaneous human albinos. METHODS: Eleven oculocutaneous human albinos (six tyrosinase negative and five oculocutaneous positive), six patients with idiopathic congenital nystagmus, and six normal control subjects participated in the study. Using a Goldmann bowl perimeter, incremental light detection thresholds were measured in the vertical meridian across the central +/- 30 degrees of the retina. Target presentation times were 1 sec for all subjects, and in the case of four albinos and one patient with idiopathic nystagmus, they were limited to the low-velocity period of each nystagmus cycle. RESULTS: For the normal control subjects, the maximum sensitivity was found to be -0.60 +/- 0.10 log units. By comparison, at 0 degrees, a range of sensitivities was obtained from the albino subjects (-0.9 to -2.1 log units) and from those with idiopathic nystagmus (-0.7 to -1.9 log units). The albinos had diverse retinal sensitivity profiles ranging from a near-normal peaked curve to a flat homogeneous profile. A variety of sensitivity profiles was also detected in those with idiopathic nystagmus, although, compared with the albino curves, a greater proportion were peaked. No sensitivity differences were found between the short and the longer target presentations. CONCLUSIONS: The variety of retinal sensitivity profiles obtained in this study suggests that, in albinism, considerable intersubject variability in the degree of foveal hypoplasia exists and that albino "foveal" function can reach near-normal levels, for at least some visual tasks.