Study of Retinal Nerve Fibre Layer Thickness in Diabetics - with and without Diabetic Retinopathy

Abstract

BACKGROUND Diabetes mellitus is a heterogeneous group of diseases, characterized by a state of chronic hyperglycemia, resulting from varied aetiologies. Diabetic retinopathy (DR) is the most common ocular complication of diabetes with 5 % of diabetics, progressing to severe visual loss of 5/200 or less. 3 Very few studies have been conducted on optical coherence tomography (OCT) changes in diabetic retinopathy in Indian scenario. We wanted to evaluate the association of retinal nerve fibre layer (RNFL) thickness with diabetic retinopathy and assess the possibility of RNFL thickness changes being a precursor to diabetic retinal changes. METHODS A cross sectional study was conducted at the Department of Ophthalmology, Acharya Vinobha Bhave Rural Hospital. A total of 120 patients were enrolled for the study and divided into four groups of equal population as controls / non-diabetics (NDM), diabetics without retinopathy (NDR), diabetics with non-proliferative diabetic retinopathy (NPDR) and diabetics with proliferative retinopathy (PDR). Patients were evaluated for visual acuity, RNFL thickness, intraocular pressure(IOP), cup disc ratio in each case and data was statistically analysed. RESULTS Mean temporal RNFL thickness in PDR group was 73.72 ± 15.22 and was statistically significant (P = 0.0001) than temporal RNFL thickness in controls (60.41 ± 7.56), NDR (61.06 ± 6.51) and NPDR (59.01 ± 5.51). Mean cup-disc disc ratio was 0.26 ± 0.08 in controls, was 0.28 ± 0.11 in NDR group, 0.32 ± 0.08 in NPDR group and 0.36 ± 0.11 in PDR group and was statistically significant (P = 0.026). However no statistically significant difference was seen in global average RNFL thickness across groups though it was more in NPDR and PDR when compared to NDM group, and was least in NDR group. CONCLUSIONS There was statistically significant increase in temporal RNFL thickness in diabetic group which worsens with the disease. Hence temporal RNFL thickness may be estimated in diabetic patients to predict transformation to diabetic retinopathy and intervene at an early stage. KEY WORDS Diabetes Mellitus, Retinal Nerve Fibre Layer, Proliferative Diabetic Retinopathy, Non Proliferative Diabetic Retinopathy