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

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

This was a cross-sectional observational study on patients with Type II diabetes mellitus from October 2020 to May 2021. Data collected include systolic/diastolic blood pressure, visual acuity, glycated hemoglobin, and central macular thickness. Diabetic retinopathy severity was categorized using the Early Treatment Diabetic Retinopathy Study classification. Photoplethysmography signals were acquired using pulse-oximeter modules (OEM-60; Dolphin Medical, Inc) measured for 90 seconds at 275 Hz sampling rate and 16-bit resolution, which records photoplethysmography fitness index, vascular risk prediction index, and vascular age.

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 ± 10.0 mmHg, P = 0.007) and diastolic blood pressure (80.0 ± 8.8 mmHg), mean glycated hemoglobin (7.6 ± 1.9%, P = 0.005), median log unit of minimal angle of resolution (0.3, interquartile range: 0.2-0.5, P < 0.001), and central macular thickness ( P = 0.003) across DR severity. Significant differences were also seen in photoplethysmography fitness index ( P = 0.001), vascular risk prediction index ( P < 0.001), and vascular age ( P = 0.001), with poorer values in severe compared with mild/moderate DR. After adjusting for age, blood pressure, and glycated hemoglobin, photoplethysmography fitness reduces by 3.3% (regression coefficient, b = -3.27, P < 0.001), vascular age increases by 2.5 years ( b = 2.54, P = 0.002), and vascular risk prediction index increases by 3.1 ( b = 3.08, P < 0.001) with every DR worsening.

More severe DR stages were associated with poorer photoplethysmography vascular markers.