Retinal Neurophysiological Parameters in Young Patients With Type 1 Diabetes

Diabetic retinopathy has prominent microvascular manifestations, but preclinical studies also find neuroglial cell abnormalities. This study aimed to examine retinal electrophysiological characteristics and their relation to diabetes duration and glycemia history in type 1 diabetes (T1D).

This cross-sectional study included 69 patients with T1D aged 6-32 (mean 16) years in equally sized subgroups of T1D duration <5 months, approximately 5 years, 10 years or 15 years. Exclusion criteria were chronic disease other than T1D, and retinal disease other than fundus photographic evidence of diabetic retinopathy. Comparison was made with 54 age-matched healthy subjects aged 8-34 (mean 17) years. Examinations included fundus imaging, electroretinography (ERG), dark adaptometry, and structural and angiographic optical coherence tomography.

In patients with T1D, ERG implicit times of the dark-adapted 85 troland seconds (Td·s) a-wave and light-adapted flicker 85 Td·s wave increased with T1D duration in simple linear regression (P = 0.041 and 0.027, respectively). In patients with >4 years T1D duration, implicit times of flicker 16 Td·s and flicker 32 Td·s in dim ambient lighting increased with higher aggregate HbA1c means (P = 0.018 and 0.036, respectively). For all T1D patients, implicit times of dark-adapted 85 Td·s a-wave and b-wave increased with higher blood glucose (P = 0.041 and 0.023, respectively). Dark adaptation rod intercept and retinal thicknesses were comparable between the groups.

This study of young T1D patients with little or no fundus photographic signs of retinopathy showed that selected ERG implicit times were longer with higher previous HbA1c levels and longer diabetes duration.