Relation of retinal nerve fiber layer thickness with blood glycemic parameters in diabetic subjects: a study from Eastern India

Abstract

Background: Diabetes affects the retina in various ways. The microvascular changes may be detected clinically by direct ophthalmoscopy. But the early neurodegenerative retinal changes are not clinically detectable. Optical coherence tomography (OCT) is a quick, reproducible, and noninvasive method of detecting retinal nerve fiber layer thickness (RNFLT). Changes in this thickness correlate with neurodegenerative retinal changes. Objectives: This study aims to generate data on RNFLT in diabetes in an Indian population. It aims to study any correlation of RNFLT with blood glucose parameters. Materials and Methods: This was a cross-sectional study on adult diabetic patients in a tertiary care medical college. RNFLT was measured by OCT in a circular area of diameter 3.6 mm around the optic nerve head. Pearson correlation study was done between the retinal thickness and blood glucose parameters: fasting (FBS) and postprandial glucose (PPBS) levels and glycated hemoglobin (HbA1C). Results: We had a total of 250 patients, which means 500 eyes. Average age of the participants was 51.6 ± 8.1 years. Out of 500 eyes, retinal thickness was low in 10.6% (95% C.I. 7.9%–13.3%). The average HbA1C level in those with low RNFLT was significantly higher than others (p < 0.001). Average RNFLT around optic nerve head was significantly correlated with blood glucose parameters. For FBS, correlation coefficient (r) was −0.5, for PPBS, it was −0.46, and for HbA1C it was −0.58. Conclusion: The RNFLT showed significant negative correlation with blood glucose parameters. Especially for HbA1C, this correlation was high in all quadrants around optic nerve head. Further studies will be needed to elucidate the relation of other blood parameters such as cholesterol with retinal thickness in diabetes.