Clinical Association between Diabetic Peripheral Neuropathy and Diabetic Retinopathy

Purpose: To quantify the association between diabetic peripheral neuropathy (DPN) and diabetic retinopathy (DR), as expressed in terms of thermal regulation of the plantar foot and vascular abnormalities in the retina.

Background: DPN accounts for around 73,000 lower-limb amputations in diabetics annually in the U.S., partially due to low compliance with periodic screening for DPN. Similarly, annual retinal screening for DR in diabetics is recommended by ADA and others. Identifying and referring individuals at risk for DPN by using biomarkers in retina could improve compliance for DPN screening.

Methods: Subjects (55-75 years) clinically diagnosed with DPN (N=20) and a set of age-matched controls (N=29) were selected. Thermal videos and retinal images were collected for all subjects. Subjects’ feet were imaged with an infrared (thermal) imager to obtain: 1) baseline temperature for 3 min, and 2) thermal recovery temperature for 10 min after a cold-patch provocation. Presence of DPN was determined by clinical examination. Retinal imaging was performed on each eye to obtain macula- and disc-centered images. A certified grader read the retinal images for severity level of DR and other retinal abnormalities. A logistic regression analysis was performed to compare retinal and thermal features, with the clinical diagnosis of DPN.

Results: A logistic regression determined a statistically significant difference (p < 0.05) in DR severity levels between DPN subjects and controls. The association between thermal features and DPN was demonstrated by statistically significant difference in recovery temperatures for both feet obtained in 1 min after cold provocation (p < 0.01), between DPN and controls.

Discussion: This study demonstrates the value of using characteristics of DR screening to identify individuals also at risk for DPN. A thermal imager located at the same screening site as a retinal camera could improve compliance with DPN screening and potentially prevent unnecessary foot complications.