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Vincent Nguyen, Agnes Choi, David Pye, Michael Kalloniatis; Electrophysiological Case Study Of Fundus Albipunctatus With Cone Dystrophy. Invest. Ophthalmol. Vis. Sci. 2012;53(14):5691.
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Fundus albipunctatus (FA) is a congenital condition of stationary night blindness characterised by white / yellow flecks located in the retinal pigment epithelium. Mutation of the gene RDH5 has been associated with the condition. FA patients show significant reduction of scotopic function with the International Society for Clinical Electrophysiology of Vision (ISCEV) standard protocol but this function improves after a few hours of dark-adaptation. It has been reported that 38 % of FA patients have a late onset cone dystrophy (Niwa et al., 2005). The aim of the study is to investigate retinal function in FA.
One FA patient with cone dystrophy and two other patients of cone dystrophy without rod dysfunction were studied. Retinal function was evaluated using multifocal, pattern and full-field ERGs. Retinal integrity was examined by optical coherence tomography (OCT).
In FA, the ISCEV scotopic protocol produced little to no response. However, prolonged dark-adaptation yielded normal scotopic response amplitude during full-field stimulation. The stimulus-intensity response function was comparable to that of normal subjects. As stimulus intensity increased, the b-wave amplitude increased steeply then saturated at higher stimulus intensities. In all cases, multifocal ERG showed bilateral reduction of photopic response amplitude around the foveal and paracentral areas. Similarly, pattern ERG showed substantial reduction of P50 response amplitude. OCT revealed general thinning of the maculae.
The scotopic retinal response in FA reacts to differing levels of light intensity suggesting functional rod photoreceptors. Bilateral reduction of foveal and paracentral vision correlates well with the areas of macula thinning in both eyes. The link between cone dystrophy and RDH5 mutation in FA remains to be explained.
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