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Purpose Diabetic macular ischemia is a vision-threatening complication of diabetes mellitus. Early detection of ischemic changes can preserve the vision. The aim of the study was to detect the early macular ischemic changes in patients with no diabetic retinopathy (NDR), using optical coherence tomography angiography, and to correlate these changes with the best-corrected distance visual acuity (BCDVA). Patients and methods A case–control study was conducted to compare 30 diabetic eyes with NDR with 30 healthy control eyes. The glycemic control was determined by glycosylated hemoglobin level less than 6.5%. The diabetic group was further subdivided into those with normal BCDVA and those with decreased BCDVA. The outcome measures included BCDVA and optical coherence tomography angiography features. Results Compared with controls, the diabetics with decreased BCDVA were found to have significantly thinner central macular thickness (P<0.001), larger foveal avascular zone (FAZ) area (P<0.001) in the superficial and deep capillary plexuses (sFAZ and dFAZ), and lower vascular density (VD) (P<0.05) regarding the central density and the superior, inferior, and temporal quadrants. In addition, they showed significantly larger associated capillary dropout areas in the superficial and deep capillary plexuses and significantly lower foveal and parafoveal VD compared with diabetics with normal BCDVA (P<0.001 and 0.05, respectively). Diabetics with normal BCDVA showed no significant difference from the controls regarding the dFAZ and VD but showed significantly lower sFAZ area (P<0.05). Conclusion Diabetic ischemic microvascular changes including decreased VD and enlarged FAZ areas precede clinically visible retinopathy and might be correlated with decreased visual acuity in patients with NDR.

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