Abstract
Abstract: :
Purpose:The present study aimed to analyze the distribution of the red/green and blue opsins in the cones from an eye of a patient with an autosomal dominant cone dystrophy. Methods: Eyes were fixed in 4% paraformaldehyde and 0.5% glutaraldehyde in phosphate buffer. Cryosections were studied by indirect immunofluorescence, using well–characterized monoclonal antibodies to the cone cytoplasm (mAbs 7G6) and polyclonal antibodies to either red/green (UW–16 and p4924A) and blue (p108B) opsins. The affected donor eye was compared to a postmortem compatible normal eye. Results:The patient’s vision was corrected to 20/200 in each eye when last seen 3 years before his death at age 85. Visual field testing showing normal peripheral boundaries and central scotomas. ERG testing showed normal rod function while the cone b–wave amplitude was reduced 40% bellow the lower limit of normal. Fundus exam showed only isolated drusen within the macula. The normal–appearing fovea was a common feature in all affected family members. Blue opsin was restricted to the outer segments of blue cones in the affected retina. In contrast, red/green opsins were distributed along the entire plasma membrane of cones with this pigment type. The cone pedicles appeared larger than normal. Also, a significant reduction in the number of cones in the outer retina of this eye was observed. Conclusions: The histological data obtained suggest that the clinical manifestation of this dystrophy is related to an abnormal distribution of the red/green opsin. Additionally, changes in the cone pedicles, as well as a reduction in the number of cones, may be correlated with the abnormal cone ERG in this patient.
Keywords: color pigments and opsins • photoreceptors: visual performance • retinal degenerations: cell biology