Comparison of RNFL Thickness and Visual Field Changes Between Diabetic Without Retinopathy and Nondiabetic Controls- A Cross-Sectional Study

Abstract

BACKGROUND Diabetes mellitus is one of the major component of metabolic syndrome and a leading cause of ocular morbidity in modern era and India will be considered to be the diabetes capital of the world. Before the onset of diabetic retinopathy, other structural and functional changes may predict the visual diminution of the individual. MATERIALS AND METHODS In this cross-sectional study in a tertiary care hospital, after inclusion and exclusion, the age-gender matched groups (diagnosed type 2 diabetes patients without diabetic retinopathy and controls without diabetes) were thoroughly examined clinically and by noninvasive and invasive examination (after proper counselling of the patient and informed consent). Then, they are tested for functional loss of retina by Humphrey FDT, GDx VCC. Comparison done between cases and controls as well as poorly-controlled and well-controlled diabetic groups. RESULTS It was found that the average RNFL thickness was significantly reduced in diabetics (mean 53.48, SD 2.69) compared to controls (mean 60.21, SD 1.87) (p<0.05). Also, in patients with uncontrolled diabetes (HbA1c >7%), the RNFL thickness was significantly reduced (mean 52.23, SD 1.31) compared to diabetics with good metabolic control (mean 56.38, SD 2.92) (p<0.05). In retinal functional testing, it was found that the Humphrey FDT mean deviation (FDT MD) and pattern standard deviation (FDT PSD) were significantly worse in diabetics (FDT MD-1.478, SD 0.386), (FDT PSD-3.485, SD 0.403) compared to normal controls (FDT MD-0.442, SD 0.536), (FDT PSD-1.438, SD 0.404). The parameters were also found to be significantly worse in uncontrolled diabetics (p<0.05). CONCLUSION To conclude, without diabetic retinopathy, functional and structural loss in retina in diabetes patients compared to age-sex matched individual and especially in poorly-controlled diabetes should be of concern as there are no detectable vasculopathy. So, early diagnosis and control of diabetes is advocated to control this functional loss.