Changes to the deep vascular plexus (DVP) foveal avascular zone (FAZ) and superficial vascular plexus (SVP) vessel density (VD), monitored with optical coherence tomography angiography (OCT-A), can predict visual outcomes and retinal sensitivity for patients with diabetic macular ischemia (DMI), according to findings published in Investigative Ophthalmology & Visual Science.
From September 2017 to September 2018, a prospective study of 56 eyes of patients with type 2 diabetes mellitus sought to evaluate the effects of DMI over a 1-year period. The participants, who had varying levels of diabetic retinopathy (DR), were imaged using OCT-A to detect the ischemia. Clinicians also recorded their best corrected visual acuities (BCVA) and microperimetry results. The researchers then repeated these procedures after 1 year, and compared changes in visual acuity and retinal sensitivity with those in parafoveal VD and FAZ.
Researchers found associations between worse visual outcomes and larger baseline DVP FAZ area on OCT-A. Additionally, the study found that larger increases in SVP VD were consistent with worsened retinal sensitivity.
In the 1-year follow-up period, 16% (9) of eyes in the study had at least 1 line worse BCVA. Another 7% (4 eyes) had at least 5% decrease in retinal sensitivity compared with baseline, the study explains. Diabetic retinopathy progressed in 12.5% of eyes. Mean [SVP] FAZ area increased (0.32 mm2 ± 0.15 mm2 to 0.39 mm2 ± 0.18 mm2, P =.003) and parafoveal VD in [DVP] decreased (49.8% ± 3.7% to 48.8% ± 2.9%, P =.040) at 1 year compared with baseline.
The researchers continue to discuss whether these results signal a higher risk of progressive visual loss for eyes with DMI detected on OCT-A, and whether this deterioration continues. However, they cite other cases that support this hypothesis.
The researchers also note that, although the number of participants was limited for this study, it is among few that exist in the current body of knowledge measuring these outcomes, as the majority of past studies of this nature are cross-sectional. They explain that future longitudinal studies with more participants will have the ability to stratify according to diabetic retinopathy severity, among other possibilities.
“Directions of future studies might want to include widefield OCT-A, to explore correlations between degree of peripheral changes with central vascular changes and its influence on functional changes prospectively,” the study explains.
Tsai ASH, Jordan-Yu JM, Gan ATL, et al. Diabetic macular ischemia: Influence of optical coherence tomography angiography parameters on changes in functional outcomes over one year. Invest Ophthalmol Vis Sci. 2021;62(1):9. doi:10.1167/iovs.62.1.9.