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L. Ziccardi, M. Piccardi, G. Iarossi, E. Merendino, A.M. Minnella, C. Manganelli, A. Fadda, B. Falsini; Temporal Frequency Response of the Macular Focal ERG: Effect of Ageing and Age–Related Maculopathy . Invest. Ophthalmol. Vis. Sci. 2004;45(13):798.
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Purpose:To evaluate the influence of ageing and age–related maculopathy (ARM) on the temporal frequency response function (TFR) of macular focal electroretinogram (FERG) Methods:Macular (18°) FERGs, in response to uniform fields (95% modulation depth, 93 cd/m2) sinusoidally flickered at different TFs between 3.7 and 52 Hz, were recorded from 13 young (mean age: 22 yrs, range: 14–29) and 10 old (mean age: 66 yrs, range: 55–80) normal subjects as well as from 18 ARM patients (stage 1–2 of Jackson et al1, mean age: 65 yrs, range: 55–80; visual acuity > 20/30). Amplitude and phase of the Fourier–analyzed response fundamental were measured. Results:In young normals, FERG TFR showed a maximum amplitude at 41 Hz, a secondary peak at 3.7 Hz, a minimum at 8–10 Hz and a high frequency roll–off. TFR of the old differed significantly (p < 0.01) from that of the young normals, showing a broad maximum at 10–14 Hz and secondary peaks at 3.7 and 41 Hz. Amplitude differences between young and old normals were found only at high TFs (32–52 Hz). TFR of ARM patients was similar to that of old normals, but with a uniform scaling in mean amplitude (–0.2 log units). FERG phase did not differ between young and old normals, but was selectively delayed at high TFs in ARM patients. FERG TFR changes in old normals and ARM patients were not mimicked by a reduction in stimulus retinal illuminance. Conclusions:Temporal response properties of macular FERG are significantly affected by normal ageing and ARM. Since FERG TFR is shaped mainly by postreceptoral activity2, the present findings support the hypothesis that a post–synaptic dysfunction, in addition to photoreceptoral losses, underlies both ageing– and ARM–related FERG changes. 1Jackson et al. JOSA 2002; 19: 185–189 2Kondo & Sieving IOVS 2001; 42: 305–312
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