Infrared thermographic investigation on the ocular surface temperature of normal subjects

It is known that the ability to measure ocular temperature accurately will increase the understanding of ocular physiology and should be a decisional support the classical diagnostic procedures. The use of ocular thermography offers great opportunities for monitoring the temperature of the anterior eye and analyzing the effects of some pathology on ocular surface temperature (OST). The aim of present work is to measure the OST of 220 healthy normal subjects, stratified according to gender and age, in order to obtain a normal temperature distribution to be used as referee values when comparing healthy versus pathological conditions. The OST is measured from five regions, located on the whole area of the anterior eye, which correspond to particular anatomic structures, through a semi-automated procedure to post-process the infrared images. The relationship between OST and independent variables (forehead skin temperature, age, gender, level of physical activity, cardiovascular risk factors including sedentary subjects, smoke, laboratory temperature, and laboratory humidity) was investigated trough linear regression models. OSTs measured from the five different ocular regions are statistically different (p-value < 0.001), even when dividing our subjects into males and females, with nasal cantus being the hottest region and the central cornea the coolest; when considering also the age effect, stratifying our subject in young, middle-age and elderly, the OST decreases when age increases significantly. The statistical analysis based on linear regression models pointed out that age, forehead skin temperature, and lab temperature are the main factors to be taken into account when exploring the OST. As OST evaluation can be important in detecting different ocular pathologies, having precise details of the variation in temperature across the ocular surface and therefore a more detailed map of the OST adjusted according to subject characteristics and environment conditions, could enhance the early diagnosis and thus the therapy effects.