Macular thickness in healthy controls and diabetics without diabetic macular edema

Aim of the Study: This study aims to evaluate the thickness of the macula in patients with diabetes but without diabetic macular edema (DME) using optical coherence tomography (OCT) and compare these findings with measurements from normal controls which may be useful for early detection of macular thickening. Patients and Methods: Two hundred subjects were included and divided into 4 equal groups: normal controls, diabetics without diabetic retinopathy (DR), diabetics with NPDR and without DME, and diabetics with PDR and without DME. Full ophthalmological evaluation was done and the fast macular OCT scan was done that divides the macula into 9 sectors. The mean ± standard deviation of macular thicknesses by area were analyzed and compared. Results: A central subfield (CS) was statistically significantly thicker in normal controls compared to diabetics with no DR with no significant difference in other sectors. Furthermore, all of the inner sectors (IS, IN, IT, II) and the ON sector were significantly thicker in normal compared to diabetics with nonproliferative DR (NPDR) group with no significant difference in other sectors. Furthermore, between all sectors except IS and IT on comparing normal versus diabetics with PDR, between nasal sectors (IN and ON) but not in other sectors on comparing diabetics with no DR versus diabetics with NPDR, between all sectors except IS on comparing diabetics with no DR versus diabetics with PDR, and between all sectors on comparing diabetics with NPDR versus diabetics with PDR. Conclusion: This study found that the fovea and perifoveal subfields of the ETDRS grid tended to be thinner in diabetics without DR than in healthy controls and still thinner in eyes with DR, but thicker in eyes with PDR than in healthy controls thus confirming that the loss of neural tissue begins in the early stages of diabetes. As diabetes develops, neurodegeneration may be masked by changes in vascular permeability that cause thickening of the retinal layers.