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G. Stifano, L. Montrone, L. Ziccardi, G. Iarossi, P. Piscopo, M. Masciullo, G. Silvestri, B. Falsini, E. Balestrazzi; Impairment of L– and M–Cone–Driven Electroretinographic Responses in Patients With Spinocerebellar Ataxias and No or Minimal Visual Symptoms . Invest. Ophthalmol. Vis. Sci. 2006;47(13):787.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate Long (L)– and Middle (M)–wavelength cone–driven electroretinographic responses in patients with spino–cerebellar ataxias (SCAs) and no or minimal visual symptoms
Focal (central 18°) electroretinograms (F–ERGs) in response to red (R)–green (G) flickering (41 Hz) uniform stimuli, modulated in counterphase with a luminance color ratio (R/R+G) corresponding to the points of L–cone and M–cone silent substitution (L–cone: 0.78; M–cone: 0.46) were recorded in 11 autosomal dominant SCA 2 genotype patients, in nine autosomal recessive AR–SCA of unknown genotype, and in 15 age–matched normal controls. All patients had normal visual acuity and moderate, non–specific color vision defects (error score 4–9) at desaturated Farnsworth D–15 test. The ERG fundamental response component amplitude and phase, isolated by Fourier analysis, were measured
When compared to controls, either SCA 2 or AR–SCA patients showed a loss in L– but not M–cone driven ERGs mean amplitude (by 35%, p < 0.05). ERG M–cone, but not L–cone–driven responses had a phase delay (by 90°, about 6.5 milliseconds, p < 0.01). L–cone driven response losses of individual patients were negatively correlated (p < 0.05) with Farnsworth D–15 error score
The results indicate an abnormality of both L– and M–cone driven retinal responses SCA clinical phenotypes usually not associated with retinal degeneration, suggesting a subclinical impairment of the cone system in the visually asymptomatic disease sub–types
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