Neuroretinal Function and Retinal Vessel Changes over One Year Are Altered by Long-Term Blood Glucose Change in Adolescent Type 1 Diabetes

Abstract

Purpose: To examine how change in long-term blood glucose concentration and aging affect neuroretinal function and retinal vascular caliber over one year in adolescents with type 1 diabetes and adolescents without diabetes.

Methods: We examined the right eyes of 82 adolescents with type 1 diabetes and no retinopathy (patient group), and 34 healthy adolescents without diabetes (control group). All were examined twice, with the exams separated by 1.1 +/- 0.2 years in each group. All subjects were 13 - 21 years old at exam 1, the patient group was 15.4 +/- 1.7 years old, and the control group was 18.1 +/- 2.7 years old. Digital fundus photographs taken at both exams were graded by a retina expert to verify the absence of retinopathy. At each exam, we measured HbA1c to determine long-term blood glucose levels, and recorded dilated photopic multifocal electroretinogram (mfERG) from the central 45 degrees. Average mfERG implicit time (IT) of each recording was calculated. Arteriole caliber (AC) and venule caliber (VC) were measured from digital optic disc photographs using IVAN software. Change was calculated as (change = exam 2 - exam 1). Linear regression analysis was used to assess associations between factors.

Results: IT change was positively correlated with HbA1c change in the patient group (P=0.030) but not in the control group (P=0.403). (Exam 1 HbA1c was 9.1 +/- 1.6% in the patient group.) We examined whether change in age might be a contributing factor. IT change and age change were not correlated in the patient group (P=0.942), but they were positively correlated in the control group (P<0.004). Next, we examined retinal vessel calibers. IT change was, marginally, negatively correlated with AC change (P=0.044) in the control group but not in the patient group (P=0.299). IT change and VC change were not correlated in either group (both P>0.229).

Conclusions: Change in neuroretinal function is correlated with change in long-term blood glucose concentration over one year in adolescents with type 1 diabetes and no retinopathy. This relationship appears to override the associations between neuroretinal function change and changes in age and arteriole caliber that we observed in healthy adolescents without diabetes.

Keywords: 498 diabetes • 509 electroretinography: clinical • 499 diabetic retinopathy