Thermal Imaging of the Ocular Surface in Thyroid Eye Disease: A Comparison between Active, Inactive and Healthy Eyes

Thermal mapping the eye: A critical review of advances in infrared imaging for disease detection

Infrared thermography (IRT) has become more accessible due to technological advancements, making thermal cameras more affordable. Infrared thermal cameras capture the infrared rays emitted by objects and convert it into temperature representations. IRT has emerged as a promising and non-invasive approach for examining the human eye. Ocular surface temperature assessment based on IRT is vital for the diagnosis and monitoring of various eye conditions like dry eye, diabetic retinopathy, glaucoma, allergic conjunctivitis, and inflammatory diseases. A collective sum of 192 articles was sourced from various databases, and through adherence to the PRISMA guidelines, 29 articles were ultimately chosen for systematic analysis. This systematic review article seeks to provide readers with a thorough understanding of IRT's applications, advantages, limitations, and recent developments in the context of eye examinations. It covers various aspects of IRT-based eye analysis, including image acquisition, processing techniques, ocular surface temperature measurement, three different approaches to identifying abnormalities, and different evaluation metrics used. Our review also delves into recent advancements, particularly the integration of machine learning and deep learning algorithms into IRT-based eye examinations. Our systematic review not only sheds light on the current state of research but also outlines promising future prospects for the integration of infrared thermography in advancing eye health diagnostics and care.

Predictive markers for anti-inflammatory treatment response in thyroid eye disease

Anti-inflammatory treatment is the primary and vital therapeutic approach for active, moderate-to-severe thyroid eye disease (TED). Accurate pretreatment prediction of treatment response is of paramount importance for the prognosis of patients. However, relying solely on the clinical activity score asa determinant of activity has led to unsatisfactory treatment outcomes. In recent years, significant advancements have been made in identifying predictive markers for anti-inflammatory treatment response in TED, clinical markers, body fluid biomarkers and imaging biomarkers. Several clinical studies have developed prediction models based on these markers. However, there is still a lack of comprehensive elucidation or comparison between the different markers. Therefore, this review aims to provide a detailed analysis of the definition, characteristics, and application of predictive markers for anti-inflammatory treatment response in TED. Through detailed literature search, 26 articles applying anti-inflammatory treatment effect prediction with a total of 1948 TED patients were used for analysis and discussion. By gaining a better understanding of the current research on predictive markers, we can accelerate and guide the exploration of treatment prediction strategies, leading us towards an era of precise therapy for TED.

Applications of Infrared Thermography in Ophthalmology

Body temperature is one of the key vital signs for determining a disease’s severity, as it reflects the thermal energy generated by an individual’s metabolism. Since the first study on the relationship between body temperature and diseases by Carl Reinhold August Wunderlich at the end of the 19th century, various forms of thermometers have been developed to measure body temperature. Traditionally, methods for measuring temperature can be invasive, semi-invasive, and non-invasive. In recent years, great technological advances have reduced the cost of thermographic cameras, which allowed extending their use. Thermal cameras capture the infrared radiation of the electromagnetic spectrum and process the images to represent the temperature of the object under study through a range of colors, where each color and its hue indicate a previously established temperature. Currently, cameras have a sensitivity that allows them to detect changes in temperature as small as 0.01 °C. Along with its use in other areas of medicine, thermography has been used at the ocular level for more than 50 years. In healthy subjects, the literature reports that the average corneal temperature ranges from 32.9 to 36 °C. One of the possible sources of variability in normal values is age, and other possible sources of variation are gender and external temperature. In addition to the evaluation of healthy subjects, thermography has been used to evaluate its usefulness in various eye diseases, such as Graves’ orbitopathy, and tear duct obstruction for orbital diseases. The ocular surface is the most studied area. Ocular surface temperature is influenced by multiple conditions, one of the most studied being dry eye; other diseases studied include allergic conjunctivitis and pterygium as well as systemic diseases such as carotid artery stenosis. Among the corneal diseases studied are keratoconus, infectious keratitis, corneal graft rejection, the use of scleral or soft contact lenses, and the response to refractive or cataract surgery. Other diseases where thermographic features have been reported are glaucoma, diabetic retinopathy, age-related macular degeneration, retinal vascular occlusions, intraocular tumors as well as scleritis, and other inflammatory eye diseases.

The Role of Thermal Camera in the Assessment of Thyroid Eye Disease Activity

Background

Thyroid eye disease (TED; also known as thyroid - associated orbitopathy, Graves ophthalmopathy) is an autoimmune inflammatory disease which presents in typical signs and symptoms such as deep orbital pain, chemosis with or without caruncular edema, unilateral or bilateral proptosis, eyelid retraction, eyelid edema or erythema, restrictive strabismus and compressive optic neuropathy.

Objective

The aim of this study was to investigate the role of thermal camera in the assessment of thyroid eye disease (TED) activity compared to the Clinical Activity Score (CAS) scale, exophthalmometry values, and thyroid hormone and antibody levels.

Methods

A total of 50 patients participated in this cross-sectional study of whom 29 were in the active phase of TED according to the sum on CAS scale and 21 patients in the inactive phase. The Flir E8® thermal camera was used to measure the temperature of the orbital area and the values were compared with the CAS scale, exophthalmometry values and thyroid hormone and antibody levels.

Results

Higher values of temperature (p>0.0001), CAS score (p>0.0001), exophthalmometry (p=0.022), FT4 (p=0.0176) and TRAb (p=0.0091) were found in patients in the active phase of TED. Temperature of orbital area showed statistically significant positive correlation with CAS scale (p=0.0001), exophthalmometry values (p=0.0022) and anti-TPO levels (p=0.019).

Conclusion

Thermal camera showed higher values of the temperature of the orbital area in patients in the active phase of the disease and positively correlated with the CAS scale, exophthalmometry findings and anti-TPO levels.