TRANSILLUMINATION OF IRIS AND SUBNORMAL VISUAL-ACUITY - OCULAR ALBINISM

Background-A common clinical sign in children with subnormal visual ac uity or slow visual development was iris transillumination. This was u sed as the inclusion criterion in a study of children shown to have a subnormal visual acuity in a general health examination at age 4 years . Methods-Refraction values, stereopsis, fundus photography, macular a nd nerve head appearance, and visual evoked response (VER) recordings were studied in 18 children. The clinical results were compared with 6 4 controls referred to the eye clinic because of subnormal vision from the general health examination or from school health care. Results-Ei ght children had VERs showing asymmetry typical for albinism. Another four had only small asymmetries on the VER, indicating a lower degree of decussation abnormality. No simple correlation of visual acuity, de gree of iris transillumination, stereopsis, or macular pathology and V ER asymmetries were found. However, marked iris transillumination in a ll four quadrants, absence of a foveal reflex, and low visual acuity w ere weakly correlated. Conclusions-In a rather homogeneous group of ch ildren with iris transillumination and subnormal visual acuity eight o f 18 had typical albino VERs. The findings of small atypical VER asymm etries in four children and no asymmetry in six children suggest that albinism may be considered as a description of a heterogeneous group o f conditions including maximal decussation rate (100%) in the chiasma to a condition with almost normal (greater than or equal to 50%) decus sation rate.