OLIGOCONE TRICHROMASY - A RARE FORM OF IN COMPLETE MONOCHROMATISM

Oligocone trichromasy is a rare form of congenital incomplete monochro matism. Patients and methods: An 11-year-old girl presented because of reduced visual acuity while color vision was almost normal. Besides a general ophthalmological examination, special psychophysical tests, s uch as perimetry, color vision tests using pseudoisochromatic plates, arrangement tests, the Nagel anomaloscope and spectral sensitivity mea surement, and electrophysiological tests (electroretinogram and electr ooculogram) were conducted. Results: The tests yielded the following: congenital nystagm, normal results at ophthalmoscopy, best visual acui ty of 0.1 monocular and 0.2 binocular. Perimetry revealed a relatively central scotoma. All color vision tests showed only mild dysfunction of the blue-sensitive cones. Findings at photopic electroretinogram we re almost completely lacking. There was no sign of progression in the last 6 years. Conclusion: Differential diagnosis includes all diseases associated with congenital nystagm, such as aniridia, diseases of the optic nerve, albinism and all forms of hereditary cone dysfunction, c one dystrophies and complete and incomplete congenital stationary mono chromatism. In the present case the findings are most congruent with o ligocone trichromasy.