Early Retinal Vascular and Neural Changes in Adolescents with Type 1 Diabetes and No Retinopathy

Abstract

Purpose: : To examine whether early retinal vascular and neural changes exist in adolescents with type 1 diabetes and no retinopathy. In addition, to evaluate whether change in blood-glucose (BG) control, measured by HbA1c value, over one year is associated with change in neural function measured by multifocal electroretinogram (mfERG).

Methods: : mfERGs, 50 deg fundus photos, and blood vessel calibers (BVC) were measured in the right eye of 84 adolescents with type 1 diabetes (no retinopathy) and 30 age-matched healthy controls. For the patients, HbA1c values at the exam and the average over the previous year were recorded. The patients’ age range was 13-19 (Mean±SD; 15.2±1.6), and best-corrected VA was 20/20 or better. The mfERG stimulus, a 103-hexagon array scaled for cone density, subtended the central 45 deg. Local mfERG P1 implicit times (IT) and N1-P1 amplitudes were measured using a template scaling method (Hood & Li, 1997). Arteriolar and venular calibers within 0.5-1.0 disc diameter away from the optic nerve head were measured with IVAN software (University of Wisconsin-Madison). T-tests were used to assess differences in BVC between patients and controls. Linear regression was used to evaluate associations between mfERG measures and HbA1c in the patients.

Results: : mfERG IT was positively associated with HbA1c at visit (R=0.31; P=0.004) and mean HbA1c over 1 year (R=0.24; P=0.04). Venular calibers were larger in patients than controls (P<0.001), but arteriolar calibers were similar (P=0.48). In a subgroup of 25 patients who were seen at 1 year follow-up, change in HbA1c over the last year was positively associated with change in mfERG IT (R=0.54; P=0.005). mfERG amplitudes were not associated with blood-glucose measures.

Conclusions: : Early vascular and neural changes exist in adolescents with type 1 diabetes and no retinopathy. The positive association between BG control and mfERG IT, and the association between change in BG control over one year and change in mfERG IT, suggest that better BG control may reduce the risk for retinal neural dysfunction. These and additional patients are being followed to better understand retinal vascular and neural changes in this population.

Keywords: electrophysiology: clinical • diabetes • retina