Characterization of the initial stages of diabetic retinal disease using optical coherence tomography (OCT) and OCT Angiography (OCTA)

Abstract

Purpose : Quantitative measurements based on OCT and OCTA distinguish eyes within the same diabetic retinopathy severity level and may have value in managing diabetic retinopathy (DR). This study evaluates the relative contribution of neurodegeneration, edema and microvascular changes in the initial stages of DR in a longitudinal cohort.

Methods : CIRRUS^TM HD-OCT 5000 with AngioPlex (ZEISS, Dublin, CA) was used to acquire structural OCT and OCTA images of eyes of subjects with type 2 diabetes with and without DR. Eyes were examined twice with an interval of one year. Thickness of retinal nerve fiber layer (RNFL) and inner nuclear layer (INL) were measured by segmenting the structural OCT data. Vessel density (VD) in the superficial plexus was measured from the OCTA data. DR severity was determined on both visits using the seven-field Diabetic Retinopathy Severity Scale (DRSS) protocol, and subjects were grouped into a 10-20 group, a 35 group and a 43-47 group. To categorize the eyes according to mechanisms of damage, a VD less than normal by 2 standard deviations (SD) on either visit was considered likely capillary closure. An RNFL thinner than normal by 1 SD was considered possible neurodegeneration. Thickening of INL by more than 2 SD compared to normal was considered likely edema.

Results : A total of 40 eyes from 23 diabetic patients (39% women) aged 53–88 years were imaged. Of 11 eyes in the 10-20 group, 2 eyes improved in DRSS and 2 eyes worsened. Of 20 eyes in the 35 group, 6 improved and 4 worsened. Of 9 eyes in the 43-47 group, 2 eyes improved and 1 worsened. In group 10-20, likely capillary closure was seen in 18% of eyes, compared to 40% in group 35, and 67% in group 43-47. Likely edema was seen in 27% of eyes in group 10-20, 40% in group 35, and 33% in group 43-47. There were no eyes with likely RNFL thinning, but 64% of eyes showed possible thinning in Group 10-20, compared to 35% in Group 35, and 33% in Group 43-47. The categories did not correlate with each other, as seen in the Venn diagrams in Figure 1.

Conclusions : Retinal degeneration, edema and microvascular alterations occur in different degree in eyes with diabetes even when classified with the same retinopathy grade. Only microvascular measurements showed correlation with disease severity.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.

 

Venn diagrams for eyes with possible RNFL loss (blue), likely VD loss (red), and likely edema (green)