Application of digital infrared thermal imaging in determining inflammatory state and follow-up effect of methylprednisolone pulse therapy in patients with Graves' ophthalmopathy

Background Inflammation can cause a local increase in temperature. Digital infrared thermal imaging (DITI) has been used to monitor the temperature distribution of human skin. Graves' ophthalmopathy (GO) is an autoimmune disease, and patients are treated with immunosuppressive agents if the ophthalmopathy is at an inflammatory state. The aim of the present study was to elucidate the feasibility of DITI in determining inflammatory state and follow-up effect of methylprednisolone pulse therapy in patients with GO. Methods Digital infrared thermal imaging was used to measure local temperatures of lateral orbit (reference point), upper eyelid, caruncle, medial conjunctiva, lateral conjunctiva, lower eyelid, and cornea, and to make thermal density plots in 14 patients (28 eyes) with GO including inflammatory signs (mean clinical activity score 2.5), and 16 normal controls (32 eyes). We also performed methylprednisolone pulse therapy in 11 patients (22 eyes) with active GO, and measured clinical activity score and local temperatures before and after treatment. The focal change in temperature after treatment and the correlation between temperature variation and change in clinical activity score were then analyzed. Thermal density plots were also compared. Results Local temperatures of the caruncle, medial conjunctiva, lateral conjunctiva, and lower eyelid of the patients were significantly higher than those of normal controls. In the 11 GO patients treated with methylprednisolone pulse therapy, the temperatures of the caruncle, medial conjunctiva, and lower eyelid were significantly decreased after treatment. Temperature variation significantly and positively correlated with a change in clinical activity score (correlation coefficient=0.8, n=22, p=0.000). The temperature decreased after treatment in patients who were responsive to methylprednisolone pulse therapy, and the thermal density plot was close to that of normal controls. Conclusions Digital infrared thermal imaging might be helpful in evaluating the inflammatory state of GO and the follow-up effect of methylprednisolone pulse therapy.