Might the refractive state in oculocutaneous albino patients be a clue for distinguishing between tyrosinase-positive and tyrosinase-negative forms of oculocutaneous albinism?

Abstract

In oculocutaneous albinism (OCA), one can distinguish between a tyrosinase-negative form (no residual activity of the enzyme tyrosinase) and a tyrosinase-positive form (with detectable residual enzymatic activity) and their respective subtypes. In infancy and early childhood the clinical discrimination between tyrosinase-positive OCA and tyrosinase-negative OCA can be very difficult. To date, only the hair-bulb L-dopa incubation test has been helpful in discriminating between the tyrosinase (ty)-negative and ty-positive forms of OCA. In 68 patients with albinism of the eye, 24 had an oculocutaneous form of albinism. We determined the ty relationship either by the L-dopa incubation test (younger patients) or by clinical appearance (older patients). We determined the full cycloplegic refraction in all patients and looked for a possible correlation of the refraction with the ty relationship. Our data suggest that an OCA patient with a hyperopic refractive error of > 4.0 D might have a ty-positive form of OCA. A patient with a moderate to high degree of myopia is more likely to have a ty-negative form of OCA. Determination of ty relationship is more reliable in patients with high degrees of hyperopia and, therefore, in patients with a ty-positive form of OCA. Statistical evaluation of the data was not possible in a sensible way due to the small number of patients involved in the present study.