THE INSTITUTO FERNÁNDEZ-VEGA CONTRIBUTES TO DECIPHER THE KEYS OF EYE DRYNESS

A group of scientists involving members of the Fundación de Investigación Oftalmológica –based in the Instituto Oftalmológico Fernández-Vega in Oviedo- has discovered the relevant role of cold thermal receptors in regulating the basal production of tears. The results have just been published in the distinguished journal «Nature Medicine».

Amongst the authors there are also researchers from the Institute of Neurosciences of the High Council for Scientific Research (CSIC) and from the Universidad Miguel Hernández de Elche. Carlos Belmonte, professor of Human Physiology at Universidad Miguel Hernández and member of the Instituto Oftalmológico Fernández-Vega has directed the study. The humidity of the eye surface, as well as that of many other mucous membranes exposed to the environment, is maintained thanks to a continuous secretion of aqueous fluid by the exocrine glands. The alteration of this process may lead to eye, mouth or vaginal dryness. These syndromes are especially common in the elderly population. In the eye, the lacrimal flow is continuous and is adjusted to the conditions of the environment (temperature, humidity) and to the frequency of blinking. Up to this moment, the process by which this basal tear secretion is maintained and regulated was unknown. According to a communiqué released by the Instituto Oftalmológico Fernández-Vega, «the study describes for the first time the neural structures responsible for feeling eye dryness and the molecular mechanism through which this regulation takes place». Cold thermal receptors are activated by moderate reductions in temperature, giving place to a feeling of coldness. «They are present in the whole body surface – as well as in the eye surface – but its function in the eye was a mystery up to now as they didn’t seem to significantly contribute to the conscious assessment of the temperature as thermoreceptors in the skin do», states the release. The study has been carried out in mice. Subsequently, the results were corroborated in humans. Researchers have demonstrated that the evaporation of the tear film, which in the interval of two blinks produces a gradual decrease in temperature in the eye surface of 1-2ºC, stimulates in the mouse the nerve endings of the corneas that are sensitive to temperature, and which function as «humidity detectors». The authors of this discovery expect it to contribute to the search of treatments against the dry eye syndrome, an alteration that «affects approximately 15% of the world population, mainly the elderly, whose secretion of tears is insufficient». This disease, amongst other symptoms, causes irritation, pain and burning sensation in the eye, and entails a loss of visual acuity. It is usually associated to vaginal and mouth dryness, which have similar symptoms, this discovery «will, therefore, also help fight the alteration in these areas of the body». As well as Carlos Belmonte, the authors of this study are Andrés Parra, Rodolfo Madrid, Diego Echevarría, Susana del Olmo, Cruz Morenilla-Palao, M. Carmen Acosta, Juana Gallar, Ajay Dhaka and Félix Viana. The Fundación de Investigación Oftalmológica – Research Foundation – includes amongst its sponsors the Fundación María Cristina Masaveu and the Obra Social de Cajastur.

Source: La Nueva España