Purchase this article with an account.
M. Michaelides, G.E. Holder, A. Webster, D.M. Hunt, A.C. Bird, J.D. Mollon, A.T. Moore; A detailed study of the phenotype of an unusual progressive cone dystrophy with supernormal rod responses . Invest. Ophthalmol. Vis. Sci. 2004;45(13):5162.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose:To characterise the detailed phenotype of a cone dystrophy with supernormal rod responses in a case series of nine patients and to shed light on possible disease mechanisms. Mutation screening of the nuclear receptor gene, NR2E3, was also undertaken. Methods:Patients were examined clinically and underwent colour fundus photography, electrophysiological testing, fundus autofluorescence (AF) imaging, and detailed psychophysical assessment. Results:The age of onset of symptoms was in the first and second decades of life. Subjects presented with reduced central vision and marked photophobia. All individuals were found to be myopic and colour vision testing revealed severely reduced colour discrimination predominantly along the red–green axes; tritan colour vision was relatively well preserved. Four individuals were aware of a progressive deterioration in visual acuity and colour vision. In one subject there was electrophysiological evidence of a progressive deterioration in retinal function. Nyctalopia is a later feature of the disorder. Fundoscopy revealed a range of macular appearances including normal fundi, mild retinal pigment epithelial (RPE) disturbance, and ‘bull’s–eye’ maculopathy. AF imaging revealed either a perifoveal ring or central macular area of increased AF. There was electrophysiological evidence of marked macular dysfunction. Electroretinography (ERG) revealed reduced and delayed cone responses. In seven individuals rod specific ERGs demonstrated supernormal and delayed rod responses. In the remaining two subjects rod responses were delayed and a profound and rapid b–wave amplitude increase with minimal increase in stimulus intensity was seen. Electrophysiological data were consistent with a post–phototransduction, but pre–inner nuclear layer site of dysfunction. Mutation screening of NR2E3 failed to identify any disease–causing variants. Conclusions:The largest case series to date has been described of the clinical, psychophysical and electrophysiological characteristics of this unusual cone dystrophy with supernormal rod responses. Whilst the definitive diagnosis can only be made with electrophysiological testing, we have presented several characteristics that may increase suspicion of this diagnosis; and can confidently identify an autosomal recessive mode of inheritance.
This PDF is available to Subscribers Only