Early functional and microcirculatory changes in patients with type 1 diabetes mellitus and no apparent diabetic retinopathy

BACKGROUND: Diabetic retinopathy (DR) is the leading complication of diabetes mellitus (DM) which is reported to affect more than one-third of the global diabetic population. Optical coherence tomography angiography (OCT-A) can help to reveal early biomarkers of DR to improve current diagnostic approach.

AIMS: To evaluate early visual functions deficiency and OCT-A changes in patients with type 1 DM (T1DM) without clinical signs of DR.

MATERIALS AND METHODS. 74 eyes of 40 T1DM patients with no apparent DR and 49 eyes of 28 healthy volunteers were included in the study. The mean duration of DM was 11,7 ± 6,1 years. All participants underwent standard ophthalmological examination, low-luminance visual acuity (LLVA) assessment, 7-field fundus photography, OCT and OCT-A. We analyzed LLVA deficit as a marker of visual function. For OCT-A scans we evaluated foveal avascular zone (FAZ) area (mm2), acircularity index (AI), vessel density (VD), skeletonized density (SD) and vessel diameter index (VDI) in superficial vascular plexus (SVP), intermediate capillary plexus (ICP) and deep capillary plexus (DCP).

RESULTS: LLVA deficit was significantly higher in T1DM patients (0,16±0,05 vs 0,10±0,04, p<0,0001). We also detected a significant difference in AI level (11,47 ± 0,24 vs 1,31 ± 0,15, p<0,0001). VD was significantly lower in T1DM patients in SVP (25,37 ± 2,24%, vs 26,67 ± 1,81%, p=0,028) and DCP (17,22 ± 3,10 % vs 18,29 ± 1,95%, p=0,015)

CONCLUSIONS: Our results demonstrate early visual functions deficiency and OCT-A changes at the preclinical stage of DR. The prognostic value of these findings will be studied during longitudinal observation.

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