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Brad Fortune, Marilyn E. Schneck, Anthony J. Adams; Multifocal Electroretinogram Delays Reveal Local Retinal Dysfunction in Early Diabetic Retinopathy. Invest. Ophthalmol. Vis. Sci. 1999;40(11):2638-2651.
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purpose. To identify local retinal abnormalities in diabetic patients with and
without retinopathy, by using the multifocal electroretinogram (M-ERG).
methods. Electroretinograms were recorded at 103 discrete retinal locations in
each eye of eight persons with nonproliferative diabetic retinopathy
(NPDR) and eight diabetic persons without retinopathy, using VERIS
(EDI, San Mateo, CA). The amplitude and implicit time of each local
(first-order) retinal response were derived and compared with normal
values obtained from 16 age-matched, nondiabetic subjects. Maps of
local response amplitude and implicit time were compared with fundus
photographs taken at the time of testing.
results. In eyes with NPDR, the implicit times of responses from retinal sites
manifesting clinical pathologic fundus lesions (e.g., microaneurysms
and focal edema), were markedly delayed (e.g., up to 7 msec from
normal). Responses from adjacent retinal sites that were more normal in
clinical appearance were also delayed, but to a lesser extent (e.g.,
2–5 msec). Smaller, yet significant local response delays were also
found in eyes without retinopathy. By contrast, local response
amplitudes bore no consistent relationship to fundus abnormalities in
eyes with retinopathy, and amplitudes were typically normal in eyes
conclusions. The M-ERG reveals local retinal dysfunction in diabetic eyes even
before retinopathy. The magnitude of delay of local ERG implicit time
reflects the degree of local clinical abnormality in eyes with
retinopathy. Local response delays found in some eyes without
retinopathy suggest that the M-ERG detects subclinical local retinal
dysfunction in diabetes. Analysis of M-ERG implicit time, independent
of amplitude, improves the sensitivity of detection of local retinal
dysfunction in diabetes.
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