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F. Simonelli, G. Iarossi, F. Testa, A. Di Meo, G. Esposito, N. Tinto, F. Salvatore, B. Falsini; Rod and Cone-Mediated Function in Choroideremia Carriers with Mutations in the REP-1 Gene . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1867.
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Purpose: To evaluate rod and cone-mediated function in X- linked choroideremia (CHM) carriers with different REP-1 gene mutations and several degrees of fundus abnormalities. Methods: Sixteen CHM female carriers (age range: 11-64 years; V.A.: 0.8-1) underwent to a complete ophthalmologic examination, including Farnsworth D-15 colour test, Goldmann perimetry, Humphrey 10-2 perimetry, Ganzfeld scotopic and photopic ERGs according to ISCEV standards and focal macular ERG (central 12°). Sixteen age-matched control subjects were also tested. Results: Fundus abnormalities included pigmented stippling and focal atrophy of retinal pigmented epithelium in both macula and periphery. When compared to controls, CHM carriers showed, on average, reduced scotopic ERG b-wave amplitude (by 20%, p < 0.01). Photopic and focal ERG amplitudes did not differ between patients and controls. Scotopic and photopic b-wave implicit times of individual patients tended to increase with increasing age, and were altered only in the elder patients. D-15 test was normal in all patients. Goldmann fields were mildly (15°) restricted in five patients. In four patients central perimetric sensitivity was abnormally reduced (p < 0.05). REP-1 gene mutations detected in female carriers were deletions, nonsense mutations, splice-site mutations and frame shift alterations. Conclusions: CHM carriers, independently from age and the type of REP-1 mutations, show losses mainly in the rod-mediated function. Instead, central and peripheral cone-mediated function tends to be more preserved and shows abnormalities only in elder patients. This finding suggests that rod photoreceptors may be the initial site of dysfunction in coroideremia carriers.
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