Rom J Morphol Embryol 2014, 55(2):257–261 ISSN (print) 1220–0522 ISSN (on-line) 2066–8279 REVIEW Ocular cells and light: harmony or conflict? SANDA JURJA 1) , MIHAELA HÎNCU 2) , MIHAELA AMELIA DOBRESCU 3) , ANDREEA ELENA GOLU 4) , ANDREI THEODOR BĂLĂŞOIU 4) , MĂLINA COMAN 5) 1) Department of Ophthalmology, Faculty of Medicine, “Ovidius” University, Constanta, Romania 2) Department of Histology, Faculty of Medicine, “Ovidius” University, Constanta, Romania 3) Department of Biology, University of Medicine and Pharmacy of Craiova, Romania 4) Research Center for Microscopic Morphology and Immunology, University of Medicine and Pharmacy of Craiova, Romania 5) Department of Histology, Faculty of Medicine, “Lower Danube” University, Galati, Romania Abstract Vision is based on the sensitivity of the eye to visible rays of the solar spectrum, which allows the recording and transfer of visual information by photoelectric reaction. Any electromagnetic radiation, if sufficiently intense, may cause damages in living tissues. In a changing environment, the aim of this paper is to point out the impact of light radiation on ocular cells, with its phototoxicity potential on eye tissues. In fact, faced with light and oxygen, the eye behaves like an ephemeral aggregate of unstable molecules, like a temporary crystallization threatened with entropia. Keywords: ocular tissues, light, phototoxicity, electromagnetic radiations, ultraviolet radiation.  Introduction The mechanism of sight is because the eye tissues are sensitive to the visible rays of the solar spectrum, which extends from 380 to 700 nm and allows, by photo- electric reaction, the recording and transfer of information conveyed by the spectrum [1]. The eye has several protective mechanisms against light damage, including miotic constriction of the pupils, light absorption by melanin in the retinal pigment epithelium (RPE), and macular antioxidants, such as lutein and zeaxanthin [2]. Lutein and zeaxanthin are members of the carotenoid family (like beta-carotene) and are the only two carotenoids in the macula [3]. Their concentration is higher in the macula than anywhere else in the body; the retinal tissue levels of these compounds depend on intake and are thus variable. They may protect against light damage because they are efficient absorbers of blue light [4–6]. All electromagnetic radiation is liable to damage the various structures of the eye if its intensity is strong enough [7–10]. However, it is mainly the visible spectrum, which is responsible for retinal injury [11, 12]. The most energetic form of radiation is ultraviolet radiation (UV). Electromagnetic radiations can cause mechanical, thermal or chemical reactions in the ocular tissues, as results of the absorption of radiation of specific wavelength; photochemical damage is produced in the ocular tissues and is defined by an unstable absorbent molecule known as chromophore. Absorption of energy results in the creation of an unstable molecular state with the formation of free radicals [13, 14]. Accumulated energy is restored in various ways resulting in numerous modifications to tissues due to interaction with the surrounding molecules. Ocular tissues defend themselves naturally using various mechanisms: filtration, molecular protection (using enzymes and anti-oxidant agents) or biological renewal (either partially or totally by means of reformation of the injured cell population). When capacities for renewal weaken or become overwhelmed, photo-induced pathologies occur [15]. The article aims to point out the damaging potential on ocular tissues of ambiental UV radiation and visible light, in a changing environment.  Effects on the cornea The cornea plays an essential role in the transmission and filtration of electromagnetic radiation, which provides vision. Its transparency is necessary for the transfer of all physical frequency elements reflected by the object or the eye’s image and focused on the retina by the visible spectrum. The cornea acts as a filter, particularly for certain ultraviolet radiation, some A and B ultraviolet rays. Radiation has a traumatic effect on the cornea, producing painful, disabling keratitis, the most spectacular of which is snow blindness. In some regions, chronic cases of keratitis are observed, that may lead to blindness. Prolonged sun exposure causes changes to the posterior tissue of the cornea, liable to lead, in old age, to edema- type problems. Chronic solar toxicity, caused by prolonged exposure to ultraviolet radiation, may lead to pterygium, climatic droplet keratopathy, squamous metaplasia or squamous carcinoma [16]. We consider that, from all the eye structures, the most damaged one is the cornea. It acts as a protection screen for the deep structures of the ocular globe, especially for the crystalline and retina. Prolonged or repeated exposure to UV radiation determines important alterations in all the microscopic structures of the cornea. R J M E Romanian Journal of Morphology & Embryology http://www.rjme.ro/