COMPARING STAGES OF DIABETIC RETINOPATHY WITH SYSTEMIC VASCULAR STATUS USING FINGER PHOTOPLETHYSMOGRAPHY.

Purpose: To evaluate systemic vascular fitness measured by finger photoplethysmography (PPG) in diabetic retinopathy (DR).

Methods: This was a cross sectional observational study on type-II Diabetes Mellitus patients from October 2020 to May 2021. Data collected include systolic/diastolic blood pressure (BP), visual acuity, HbA1c, and central macular thickness (CMT). DR severity was categorised using the ETDRS classification. PPG signals were acquired using pulse-oximeter modules (OEM-60, Dolphin Medical Inc) measured for 90 seconds at 275Hz sampling rate and 16-bits resolution which records photoplethysmography fitness index (PPGF), vascular-risk prediction index (VRPI) and vascular age (VascA).

Results: One-hundred-and-forty-one patients were equally distributed into six DR categories. Mean age was 58.8±9.9 years, with female-to-male ratio of 1.27. There were significant differences in mean systolic (125.5±10.0mmHg, p=0.007) and diastolic-BP (80.0±8.8mmHg), mean HbA1c (7.6±1.9%, p=0.005), median LogMAR (0.3, IQR:0.2-0.5, p<0.001) and CMT (p=0.003) across DR severity. Significant differences were also seen in PPGF (p=0.001), VRPI (p<0.001) and VascA (p=0.001), with poorer values in severe compared to mild/moderate DR. After adjusting for age, BP and HbA1c, PPGF reduces by 3.3% (regression coefficient, b= -3.27, p<0.001), VascA increases by 2.5 years (b=2.54, p=0.002) and VRPI increases by 3.1 (b= 3.08, p<0.001) with every DR worsening.

Conclusions: More severe DR were associated with poorer PPG vascular markers.