Light and ocular immunityHajrasouliha, Amir Reza; Kaplan, Henry J.Current Opinion in Allergy and Clinical Immunology: October 2012 - Volume 12 - Issue 5 - p 504–509 doi: 10.1097/ACI.0b013e328357d3a4 EYE ALLERGY: Edited by Leonard Bielory and Stefano Bonini Abstract Author Information Purpose of review Current scientific evidence suggests that the systemic immune response is affected by exposure to light. During the past century man has been exposed for the first time in evolution to light at night, as well as increasing ultraviolet radiation through depletion of the ozone layer in our atmosphere. These ecological changes have enhanced the impact of light on our systemic immune response. We will review the effect of light on the systemic immune response with particular emphasis on ocular immunity. Recent findings Visible light is now recognized to be important in the maintenance of immune privilege within the eye; however, little is known about the mechanism through which this effect occurs. Recent studies suggest that the generation of regulatory T cells involved in immune privilege within the eye is dependent on retinoic acid formation by retinal pigment epithelial cells. Light is also important in modulation of multiple pathways including adjustment of circadian rhythm and production of vitamin D. Summary Light regulates our biologic systems in many different ways. Its effect on the systemic immune response suggests that it is important in maintaining health, as well as in the induction of disease. A better understanding of the interaction of light with our biologic systems may allow new preventive measures to avoid disease and novel forms of treatment. Department of Ophthalmology and Visual Sciences, Kentucky Lions Eye Center, University of Louisville, Louisville, Kentucky, USA Correspondence to Henry J. Kaplan, Kentucky Lions Eye Center, Department of Ophthalmology and Vision Sciences, University of Louisville, 301 E. Muhammad Ali Blvd., Louisville, KY 40202, USA. Tel: +1 502 852 3716; fax: +1 502 852 4595; e-mail: email@example.com Copyright © 2012 Wolters Kluwer Health, Inc. All rights reserved.