Abstract
Oligocone trichromacy (a subtype of incomplete achromatopsia) is a congenital and stationary cone dysfunction with trichromatism. It is characterized by reduced visual acuity and day blindness, a reduced amplitude of the photopic electroretinogram, a normal fundus and normal color vision.
It is hypothesized that these patients might have a reduced number of normal functioning cones with preservation of the three cone types. As far as we know, this is the first report in which this hypothesis is tested by screening the foveal cone photopigment in four patients with oligocone trichromacy. Foveal densitometry was performed (a technique measuring the foveal cone photopigment density difference and its time constant of photopigment regeneration) and color matching; increment threshold spectral sensitivities were also measured. A reduced density difference of the foveal cone photopigment with a normal time constant of photopigment regeneration was found in all patients. The color matching data were normal. Increment threshold spectral sensitivity was tested in two patients; the results were normal.
We conclude that foveal cone photopigment screening in oligocone trichromacy confirms in vivo the hypothesis of a reduced number of cones (decreased density differences) with otherwise normal functioning cones.
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Keunen, J.E.E., De Brabandere, S.R.S., Liem, A.T.A. (1995). Foveal densitometry and color matching in oligocone trichromacy. In: Drum, B., et al. Colour Vision Deficiencies XII. Documenta Ophthalmologica Proceedings Series, vol 57. Springer, Dordrecht. https://doi.org/10.1007/978-94-011-0507-1_24
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DOI: https://doi.org/10.1007/978-94-011-0507-1_24
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