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T.S. Vajaranant, G.A. Fishman, J.P. Szlyk, P. Grant–Jordan, M. Lindeman, W. Seiple; Mosaic Retinal Dysfunction in Obligate Carriers of Choroideremia . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3759.
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© ARVO (1962-2015); The Authors (2016-present)
To test whether choroideremia carriers have a mosaic pattern of functional retinal defects as noted in carriers of x–linked retinitis pigmentosa.
Four obligate choroideremia carriers with normal vision underwent a complete ophthalmic examination, including Humphrey visual field testing (24–2) and multifocal electroretinogram (mfERG, VERIS system: 103–scaled hexagons). The amplitude (a–scales) and implicit time (t–scales) scaling were measured by the algorithm of Hood and Li. The a–scales and t–scales were reported to be abnormal when they were outside 2 standard deviations from the mean of age–similar normally–sighted control subjects (p < 0.05).
Three carriers with mild to moderate pigmentary changes in the macula showed widespread but patchy mfERG abnormalities with both statistically significant amplitude reductions and implicit time delays (p < 0.05). Only one of the three carriers showed a mild visual threshold abnormality on Humphrey visual field testing. The fourth carrier with a clinically normal fundus and normal Humphrey visual field showed isolated areas of correlated amplitude and implicit time abnormalities.
We demonstrated a mosaic pattern of retinal dysfunction by mfERG testing in carriers of choroideremia with normal vision. Our findings are consistent with the Lyon hypothesis of random X–chromosome inactivation. The mfERG is potentially sensitive to detect local retinal dysfunction in choroideremia carriers even when the fundus examination is normal.
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