Ocular surface heat flux density as a biomarker related to diabetic retinopathy (pilot study)

Abstract

IntroductionAssessing heat flux (HF) is necessary for a complete understanding of heat transfer in the human body, as temperature measurements alone are insufficient. A comprehensive heat transfer evaluation will expand our knowledge of human physiology and create new diagnostic possibilities, including ocular pathology. PurposeTo evaluate ocular surface HF density in patients with diabetic retinopathy (DR). Material and methodsThis study was pilot, prospective, open-label and non-interventional. Eighty-four DR patients (168 eyes; aged 18–88 years) and 30 healthy volunteers (60 eyes; aged 18–85 years) were under our observation. A bilateral ophthalmic examination including biomicroscopy, ophthalmoscopy, optical coherence tomography, and measurements of the ocular surface temperature (OST) and HF density was performed in all cases. ResultsThe mean OST and mean ocular surface HF density were 34.7 ± 0.7 °С and 7.2 ± 1.3 mW/cm2, respectively. The OST was positively correlated with HF density (r = 0.36; P = 0.005). We found that the ocular HF density was negatively correlated with age in DR patients (r = - 0.5; P = 0.001). There was a positive correlation between the choroidal thickness and the ocular surface HF density (r = 0.6; p = 0.001) compared to the OST (r = 0.3; p = 0.1). The ocular surface HF density in proliferative DR was significantly lower than in non-proliferative DR and healthy individuals. The ROC curve for determining proliferative DR with the ocular surface HF density was calculated (76.67% sensitivity and 85.51% specificity, with an area under the curve of 0.877). Mean ocular surface HF density values in proliferative DR with rubeosis were significantly lower than those without rubeosis. ConclusionWe believe that the ocular surface HF density in DR patients reflects the heat transfer intensity and can serve as a physiologic biomarker of intraocular blood flow insufficiency. Direct measurement of ocular surface HF density may be useful for the early detection of DR patients at high risk of neovascular glaucoma. Further studies are necessary to evaluate changes in ocular HF values in patients with DR following various treatments.