Purchase this article with an account.
J. Carroll, M. Neitz, J. Wolfing, D. Gray, J. Neitz, D.R. Williams; Different genetic causes of red–green color blindness give rise to different retinal phenotypes as assessed with adaptive optics . Invest. Ophthalmol. Vis. Sci. 2004;45(13):4341.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: Historically, two competing models for red–green color vision defects have been considered. The replacement model hypothesizes that L and M photoreceptors are preserved, but the normal photopigment of one class is replaced either with an anomalous pigment or with a pigment from the opposite class. The loss model hypothesizes that one entire class of photoreceptor is lost. Recent evidence reveals that a variety of genetic causes of red–green color vision deficiency exist, ranging from deletion of genes encoding one class of photopigment, to the presence of genes encoding non–functional pigment. This genetic heterogeneity is compatible with both the loss and replacement models, depending on the precise genetic defect. Here we used adaptive optics to directly assess the cone photoreceptor mosaic in individuals with genetically defined color vision defects to determine whether different genetic scenarios were consistent with the replacement versus the loss model. Methods: Color vision phenotypes were determined based on color matching performance on an anomaloscope (Oculus, HMC) in addition to standard color vision tests. The genetic cause of each subject's defect was determined using previously described methods. Retinal images of the cone mosaic were obtained using adaptive optics, and cone density was compared to that of color normals. Results: A number of genetic causes for red–green color blindness were identified. A deuteranope, whose defect was caused by an inactivating mutation in his M–gene had areas of retina devoid of waveguiding cones, resulting in a peak cone density ∼30% below normal, consistent with a loss model. The anomalous trichromats and single–gene dichromats we examined had cone densities within normal limits, consistent with the replacement model. Conclusions: This finding provides the first direct demonstration that color blindness can arise from the loss of an entire class of photoreceptor, as well as from the replacement of one class by another.
This PDF is available to Subscribers Only