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Yoshiaki Shimada, Masayuki Horiguchi, Atsuhiro Tanikawa, Manami Kuze; A Functional Index Of Diabetic Macular Edema: Disappearance Of The Slow Positive Component (P50) In The First Slice Of The Second Order Kernel Of Multifocal ERG In The Fovea. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6082.
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To establish a functional index of diabetic macular edema (DME) by use of multifocal electroretinogram (mfERG).
mfERGs were recorded with a 75 Hz base rate, 2.67 cds/m2 stimulus intensity, 37 stimulus hexagons, 3 min 38 sec recording time and 10-300 Hz band-pass filter, from 24 eyes with DME (visual acuity, 20/200-20/25), 24 eyes of 24 diabetic patients without retinopathy and 40 healthy volunteers (controls). The difference among individuals was investigated on a case by case basis.
At the centermost element corresponding to the fovea, approximately 2 degrees in diameter, a positive component with a long peak time around 50 (47.5-53.3) ms (P50) was observed in the first slice of the second order kernel (K2.1) in all controls. The P50 was missing in all 24 eyes with DME (24/24) . With diabetic patients without retinopathy, only 5 eyes showed the disappearance of the P50 (5/24).
Healthy foveal K2.1 carries many prolonged wavelets. The prolongation can be attributable to the lengthened cone axons known as fibers of Henle, and the abundance of the slow responses reflects a long adaptive memory in the fovea. P50 is observed with a fast base rate, so resonance effects of overlapping many successive higher order kernels and slices may contribute to the P50. It has been reported that the K2.1 is attenuated in diabetic eyes. However, they were only statistical implications, not helpful to diagnosis on a case by case basis. Disappearance of P50 can be a useful index of the impaired foveal function with DME.
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