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M. T. McFarlane, G. Mirabella, T. Wright, C. A. Westall; Targeting Electrophysiological Markers of Short-Wavelength Visual Pathway Dysfunction in Adolescents With Type 1 Diabetes. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3259.
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To identify electrophysiological markers of short-wavelength loss in adolescents with Type 1 Diabetes (T1D).
Visual evoked potentials (VEPs) were recorded to black-white luminance as well as isoluminant short-and long-medium- vertical, sinusoidal gratings (1cyc/deg) in 50 patients with T1D (15 ± 1.88 years old) and 42 controls (16 ± 3.64 years old). VEP latencies were evaluated in response to pattern onset-offset gratings (2Hz) presented at 40, 20 and 10% contrasts. Short-wavelength electroretinograms (sERGs) were recorded using blue flashes (peak 410nm) against an amber (594 nm) background in 18 of the patients with T1D (15 ± 1.53 years old) and 18 controls (17 ± 3.88 years old). The outcome measures were implicit time of the b-wave and amplitude of the photopic negative response (PhNR) measured from baseline at 100 ms. Ambient blood glucose was maintained between 4-10mmol/L before and during testing. Hemoglobin A1c (HbA1c), a measure of long-term blood glucose control, was 8.90% ± 1.38 in the patient population. Patients with Diabetic Retinopathy were excluded.
VEP latencies to short-wavelength stimuli were delayed in those with T1D compared with controls at all contrasts (repeated measures regression, p=0.004). Responses to long-medium wavelength and achromatic stimuli were not delayed significantly in those with T1D. sERG implicit times were delayed (p=0.0002) and PhNR amplitudes were decreased (p=0.03) in adolescents with T1D compared with controls. Age or HbA1c were not correlated with the ERG measures.
Short-wavelength VEPs show a dysfunction in the retinal-striate short-wavelength pathway in adolescents with T1D. sERG implicit time delays identified dysfunction in the outer/middle retina while PhNR results suggest dysfunction in the inner retina. As HbA1c is a known risk factor for Diabetic Retinopathy, the lack of correlations with sERG implicit time or PhNR suggests that these outcome measures are not good biomarkers for risk of developing retinopathy.
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