Evaluation of metabolite changes in visual cortex in diabetic retinopathy by MR-spectroscopy

PurposeTo evaluate metabolite changes in the visual cortex of diabetic patients with nonproliferative or proliferative diabetic retinopathy by Magnetic Resonance Spectroscopy (MRS).Materials and Methods15 normal subjects (group 1), 15 patients with diabetes who did not have diabetic retinopathy (group 2), 15 patients with nonproliferative diabetic retinopathy (NPDR) (group 3), and 15 patients with proliferative diabetic retinopathy (PDR) (group 4) were included in the study. Furthermore, diabetic patients were divided into two groups according to HbA1c levels (Group A: 20 patients, HbA1c < 8%; Group B: 20 patients, HbA1c > 8%). In all cases' left visual cortex, amounts of N-acetyl-aspartate (NAA), choline (Cho), and creatine (Cr) were measured by MRS. NAA/Cr, Cho/Cr, and NAA/Cho ratios were calculated. Furthermore, all cases' complete blood count (CBC) and biochemical parameters were evaluated.ResultsThere was no statistically significant difference for NAA/Cr, Cho/Cr, and NAA/Cho ratios between groups 1, 2, 3, and 4 (P > 0.05). However there was a statistically significant difference for NAA/Cr and NAA/Cho ratios between groups A and B (P < 0.05). There was no statistically significant difference for Cho/Cr ratio between groups A and B (P > 0.05).ConclusionAlthough NAA/Cr and NAA/Cho ratios decrease in the visual cortex while diabetic retinopathy progresses, these decreases are not statistically significant. While HbA1c levels increase, the NAA concentration decreases in the visual cortex which indicates neuronal loss. The metabolite changes in the visual cortex are associated with acute events rather than chronic.