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Benedetto Falsini, Antonello Fadda, Giancarlo Iarossi, Marco Piccardi, Doriana Canu, Angelo Minnella, Sebastiano Serrao, Luigi Scullica; Retinal Sensitivity to Flicker Modulation: Reduced by Early Age-Related Maculopathy. Invest. Ophthalmol. Vis. Sci. 2000;41(6):1498-1506.
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purpose. To evaluate retinal, cone-mediated flicker sensitivity (CFS) in
age-related maculopathy (ARM) by quantifying response gain and
threshold of the focal electroretinogram (FERG) to flicker modulation.
methods. Nineteen patients with ARM (visual acuity ≥20/30) and 11 age-matched
control subjects were examined. Twelve patients had less than 20 soft
drusen in the macular region and no hyper-/hypopigmentation (early
lesion), whereas seven had more than 20 soft drusen and/or focal
hyper-/ hypopigmentation (advanced lesion). Macular (18°) FERGs were
elicited by a sinusoidally flickering (41 Hz) uniform field (on a
light-adapting background) whose modulation depth was varied between
16.5% and 94%. Amplitude and phase of the response’s fundamental
harmonic were measured.
results. In both control subjects and patients with ARM, log FERG amplitude
increased with log stimulus modulation depth with a straight line
(power law) relation. However, the slope (or gain) of the function was,
on average, steeper in control subjects than in patients with either
early or advanced lesions. Mean FERG threshold, estimated from the
value of the log modulation depth that yielded a criterion response,
did not differ between control subjects and patients with early lesions
but was increased (0.35 log units) compared with control subjects in
those with advanced lesions. In both patient groups, but not in control
subjects, mean FERG phase tended to delay with decreasing stimulus
conclusions. Retinal CFS losses can be detected in ARM by evaluating the FERG as a
function of flicker modulation depth. Reduced response gain and phase
delays, with normal thresholds, are associated with early lesions.
Increased response thresholds, in addition to gain and phase
abnormalities, may reflect more advanced lesions. Evaluating CFS by
FERG may directly document different stages of macular dysfunction in
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