Autosomal recessive ocular albinism (AROA) is a disorder characterized by reduced pigmentation of the retina and iris, hypoplastic fovea, variably reduced visual acuity and nystagmus. Pigmentation of the skin and hair is normal, but is usually slightly lighter than in unaffected sibs. We analysed 12 unrelated patients with AROA, and found that two had abnormalities of the tyrosinase (TYR) gene. These two patients were each a compound heterozygote for a different pathologic mutant allele and an allele containing a 'normal' polymorphism, Arg402Gln, which results in a tyrosinase polypeptide with reduced thermal stability. In these patients, AROA thus appears to represent a clinically mild form of OCA1, with a fixed visual deficit resulting from low tyrosinase activity during fetal development but with normal pigmentation of the skin and hair postnatally.
Superior oblique myokymia (SOM) is an unusual eye movement disorder characterized by recurring episodes of vertical and torsional microtremor of an eye. Visual symptoms include vertical and torsional diplopia, monocular oscillopsia, and tremerous sensations. The disorder is caused by an abnormal firing of the superior oblique muscle in the affected eye. Three cases of SOM will be presented. One of these patients had improvement of her symptoms from the antidepressant drug mirtazapine (Remeron).
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