Abstract
Purpose: :
To identify electrophysiological markers of short-wavelength loss in adolescents with Type 1 Diabetes (T1D).
Methods: :
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.
Results: :
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.
Conclusions: :
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.
Keywords: diabetic retinopathy • color vision • electrophysiology: clinical