Diabetic Macular Ischemia: Influence of Optical Coherence Tomography Angiography Parameters on Changes in Functional Outcomes Over One Year

Abstract

Purpose: To prospectively evaluate whether diabetic macular ischemia detected with coherence tomography angiography (OCTA) is associated with change in functional outcomes over a period of one year.

Methods: This is a one-year prospective, observational study that included 56 eyes with varying levels of diabetic retinopathy. All participants underwent best corrected visual acuity evaluation, swept-source OCTA and microperimetry at baseline and repeated at one year. Parafoveal vessel densities (VD) and foveal avascular zone (FAZ) areas were generated from OCTA in the superficial and deep vascular plexuses. The influence of baseline and change in OCTA parameters on change in visual acuity and retinal sensitivity over one year was evaluated.

Results: Over the one-year follow-up period, 16% (9) of eyes had at least one line worsening in BCVA and 7% (4) of eyes had at least 5% decrease in retinal sensitivity compared to baseline. Diabetic retinopathy progressed in 12.5%. Mean superficial vascular plexus (SVP) FAZ area increased (0.32 ± 0.15 to 0.39 ± 0.18 mm2, P = 0.003) and parafoveal VD in deep vascular plexus (DVP) decreased (49.8 ± 3.7% to 48.8 ± 2.9%, P = 0.040) at one year compared to baseline. In the multivariate regression analysis, larger baseline DVP FAZ area was associated with worsening of BCVA over one year (β = 0.16 logMAR per mm2, 95% CI 0.02 to 0.31, P = 0.032). In addition, larger decreases in SVP VD (β = -4.18 db per 10% decrease, 95% CI -6.55 to -1.80, P = 0.002) was associated with worsening of retinal sensitivity over one year.

Conclusions: Progression of parafoveal microvasculature changes over one year can be detected using OCTA. Larger baseline DVP FAZ area on OCTA is predictive of worsening in visual outcomes, and larger decreases in SVP VD were associated with worsening of retinal sensitivity over a course of one year in diabetic individuals.

Figure 1.

( A ) OCTA Vessel density grid. (B) Microperimetric protocol. A 13-stimuli microperimetric grid (1500 µm × 1500 µm) superimposed on a 3 mm × 3 mm enface OCTA scan centered on the fovea.

Figure 2.

Representative cases. (A) Patient A is a type 2 diabetic for 23 years, diagnosed with mild NPDR in the right eye. She presented with acceptable parafoveal VD and FAZ areas in both the SVP and DVP at baseline. OCTA metrics was associated with a good vision of 0.1 logMAR at baseline that was maintained at one-year follow-up. (B) Conversely, Patient B, is a type 2 diabetic for 12 years, diagnosed with moderate NPDR in the left eye. He presented with a larger FAZ area in the DVP which was associated with poorer vision of 0.2 logMAR at baseline, which further deteriorated to 0.3 at one-year follow-up despite no progression of DR.