Changes in Blood Glucose Control and Multifocal Electroretinogram (mfERG) in Adolescents with Type 1 Diabetes and No Retinopathy

Abstract

Purpose: : To evaluate the relationship between change in blood glucose control and local retinal function over one year in adolescents with type 1 diabetes and no retinopathy.

Methods: : mfERG, HbA1c, and 50 deg fundus photos were obtained twice (1 year apart) from the right eyes of 63 adolescents with type 1 diabetes. A retina expert graded fundus photos from both visits and 8 patients were excluded due to retinopathy. Patients’ age range was 13-19 years (Mean±SD; 15.4±1.7), and best-corrected VA was 20/20 or better. The mfERG stimulus was comprised of 103 hexagons, scaled for cone density, that reversed in polarity according to a pseudorandom sequence (m-sequence), and subtended 45 deg. Local first order mfERG P1 implicit times (IT) were calculated using a template scaling method (Hood & Li, 1997). IT Z-scores were also calculated based on data collected from 30 age-matched control subjects. Associations between mfERG IT and HbA1c were evaluated using linear regression analyses.

Results: : For the 55 patients with no retinopathy, change (visit 2 - visit 1) in mean mfERG IT was associated with change in HbA1c (r=0.35; p<0.01). The group mean change in mfERG IT was 0.23 ± 0.44 ms. 14 patients (25%) had worsening retinal function from visit 1 to 2, 39 (71%) had no functional change, and 2 (4%) had functional improvement. 27 patients (49%) had no mfERG IT abnormalities (Z-score ≥2) at both visits. A correlation between change in the number of abnormal locations and change in HbA1c existed in 15 patients with 6 or more abnormal locations at either visit (r=0.59; p=0.02). In a subgroup of these patients who had more abnormal locations in visit 2, the persistence of local IT abnormalities was high with 120 out of 129 (93%) locations remaining abnormal in visit 2.

Conclusions: : In adolescents with type 1 diabetes and no retinopathy, one-year change in blood glucose control, measured as HbA1c change, was associated with change in retinal function. Persistence of local abnormalities was high. These observations show the high sensitivity of the mfERG in evaluating retinal function in this group of patients, and suggest that improving blood glucose control slows the decline in neuroretinal function produced by adolescent type 1 diabetes.

Keywords: diabetes • electroretinography: clinical • diabetic retinopathy