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Jason Comander, Carol Weigel-DiFranco, Eliot L Berson; Long-term Vision Changes in Carriers of X-linked Retinitis Pigmentosa. Invest. Ophthalmol. Vis. Sci. 2014;55(13):1393.
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Female carriers of X-linked retinitis pigmentosa (XLRP) can experience visual loss to varying degrees. However, due to relatively small published case series, the frequency and severity of visual loss in XLRP carriers is not well described.
This study presents cross-sectional data (N=242 patients) and longitudinal data (N=34 patients, >3 years followup, spanning 42 years of records) from carriers of XLRP.
In the majority of patients, there is some degree of abnormality, with 56% of eyes showing a definite abnormality on at least one psychophysical test (visual acuity, visual field area, or dark adaptation final threshold). Among obligate carriers, 97% (64/66), but not 100%, have abnormal ERG 30 or 0.5 Hz amplitudes. Strikingly, ERG amplitudes and their rates of decline, on average, are almost exactly half of the lower limit of normal, supporting the hypothesis that random X-inactivation causes half of the photoreceptors to be affected. However, any individual eye can be more or less affected; for example 1.7% (4/242) of patients are legally blind based on visual acuity (≤20/200 in both eyes). XLRP carriers with RPGR mutations (N=99) were similar to carriers with RP2 mutations (N=13).
Most carriers of XLRP are mildly or moderately affected, but rarely they become legally blind. These data present a mixed prognosis for carriers of XLRP; individualized clinical predictions, carrier detection, and genetic implications are discussed.
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