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C.M. Poloschek, K. Williamson, V. van Heyningen, G. Wildhardt, B. Lorenz; Correlation Between Genotype and Retinal Alterations in Aniridia as Measured With the Full–field and Multifocal Electroretinogram . Invest. Ophthalmol. Vis. Sci. 2005;46(13):677.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To characterize changes in the electroretinogram (ERG) in aniridia and to relate functional changes to specific mutations in PAX6. Methods: A total of 25 patients (mean age 26 years, range 3 – 66 years) from 18 families has been included so far based on an aniridia phenotype. Full–field ERGs and multifocal ERGs (mfERG, 103 stimulus elements subtending a visual angle of 25 degrees) were recorded according to the current standards and guidelines, respectively, of the International Society for Clinical Electrophysiology of Vision (ISCEV). Mutations in PAX6 were detected by single strand conformation polymorphism or by DHPLC analysis and characterized by sequencing on both strands. Results: To account for differences in age, full–field ERG amplitudes and implicit times were normalized to the median of age–matched normal values for each response. Amplitudes of the scotopic system were reduced to a median of 0.8 (rod response) and 0.84 (combined response b–wave). Photopic responses showed greater reduction (median single flash cone b–wave: 0.64, flicker: 0.52). Oscillatory potentials (OP) had lowest amplitudes (median 0.35). Implicit times were either normal or only slightly prolonged. MfERGs could be obtained only from patients without nystagmus (4 patients). Amplitudes of ring 1 and 2 were significantly reduced (p = 0,05). Except for one patient, corresponding photopic full–field ERG amplitudes were in the range of age–matched normal control values. To date mutations in PAX6 have been identified in 4 families. In a Q221stop mutation in exon 8 amplitudes of all responses were lower than in mutations found in exon 5 (438delC), exon 6 (543delT), both frame shift mutations, and in a missense mutation in exon 6 (S49F). Conclusions: A broad range of ERG alterations manifest in aniridia. The photopic system seems to be relatively more functionally disturbed than the scotopic system. MfERG changes reflect abnormal macular development. OPs appear to be the most affected response. This might be due to impaired integrity of inner retinal cells, an abnormal input from photoreceptors or a combination of both. At this stage, to further specify the impact of a particular site of mutation in PAX6 on visual function, more mutations need to be identified.
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