Ocular Phototoxicity. J Photochem Photobiol B 2001 Nov 15;64(2-3):136-43
"We have known for some time that exposure to intense artificial light and sunlight either causes or exacerbates age-related ocular diseases. We now know many of the reasons for these effects"
"Because the eye is constantly subjected to ambient radiation, each portion of the eye contains very efficient defense systems. ... Unfortunately, most of these protective enzymes decrease beginning at 40 years of age.
"The leading cause of irreversible blindness in the increasingly aged population is macular degeneration ...Visible and/or blue light are particularly damaging to the aging retina because it has lost its anti-oxidant protection... At the same time these protective agents are becoming depleted, the aging retina also accumulates fluorescent phototoxic chromophores. Visible light activates these chromophores and produces reactive oxygen species (ROS). The production of ROS in aged RPE (retinal pigment epithelium) cells leads to apoptosis and cell death. One of the functions of the RPE is to transport nutrients to the photoreceptor cells. With the death of the RPE cells the photoreceptor cells are no longer nourished and they die off. The result is as loss of vision." Abstract
Apoptosis in the Retina: The Silent Death of Vision
News in Physiological Sciences 2000; 15(3):120-124
Charlotte E. Remé, Christian Grimm, Farhad Hafezi, Andreas Wenzel and Theodore P. Williams
"The photoreceptors of the retina present a puzzling phenomenon: they can be injured or even destroyed by light, the very element they are designed to detect."
"An intriguing question is whether certain wavelengths of the visible spectrum may preferentially induce apoptosis in the retina. Linked to this is the inquiry about the chromophore(s) and the death pathways mediating light-induced apoptosis. We obtained a striking all-or-none response when albino rats were exposed to either monochromatic blue light of 403 nm (3.1 mW/cm2) or monochromatic green light of 550 nm (8.7 mW/cm2)... No apoptosis and no other light-induced lesions could be found in green light-exposed eyes, whereas massive apoptotic cell death occurred after illumination with blue light". Full Article
Retinal Photodamage. J Photochem Photobiol B 2001 Nov 15;64(2-3):144-61
Boulton M, Rozanowska M, Rozanowski B.
"The retina represents a paradox, in that, while light and oxygen are essential for vision, these conditions also favour the formation of reactive oxygen species leading to photochemical damage to the retina. Such light damage seems to be multi-factorial and is dependent on the photoreactivity of a variety of chromophores endogenous to the retina."
"Light is essential for vision but the trade off is the generation of potentially damaging reactive oxygen species within the eye."
"It is tempting to suggest that the inter-individual variability in the onset and severity of disease dependent on both light exposure and the concentration of retinal chromophores." Abstract
Solar Radiation and Age Related Macular Degeneration.
Survey of Ophthalmology 1988; 32(4): 252-269
"The high-energy segment of the visible region (400-500 nm) is enormously more hazardous than the low energy portion (from 500-700 nm). Because the transition occurs at the border between the perceived colors of green and blue, the phenomenon is known as blue light hazard." Abstract
Ocular Injury Due to Light Toxicity.
International Ophthalmology Clinics 1988;28(3):246-250
"Blue-light injury can result from viewing either extremely bright light for a short time or less bright light for a longer time."
"Excessive light exposure in the elderly may be particularly risky, since the biological repair processes at the cellular level are generally considered to be less effective as one ages." Abstract
Prevention of Photoreceptor Apoptosis by Activation of the Glucocorticoid Receptor.
Invest Ophthalmol Vis Sci 2001 Jun;42(7):1653-9
Wenzel A, Grimm C, Seeliger MW, Jaissle G, Hafezi F, Kretschmer R, Zrenner E, Reme CE.
"Evidence has accumulated that excessive light exposure may promote age-related and inherited retinal degeneration, in which photoreceptor death by apoptosis leads to loss of vision." Abstract
Evidence for a Circadian Rhythm of Susceptibility to Retinal Light Damage.
Photochem Photobiol 2002;75(5): 547-53
Vaughan DK, Nemke JL, Fliesler SJ, Darrow RM, Organisciak DT
"In all animals, retinal light damage was the most severe when intense light exposure began during the dark period. However, this severe damage was significantly reduced by pretreatment with the antioxidant.... Our data support the notion of a circadian rhythm of light damage susceptibility that peaks in the dark period and yet can be modulated by the exogenous administration of an antioxidant." Abstract
Observation of Ultrastructural Changes in Cultured Retinal Pigment Epithelium following
exposure to Blue Light.Graefes Archives for Clinical and Experimental Ophthalmology 1998; 236(9):696-701
Pang J, Seko Y, Tokoro T, Ichinose S, Yamamoto H
"The retina can be damaged by light even when levels of energy are well below the threshold for thermal damage, and the experimental damage of the retinal pigment epithelium (RPE) may be induced more easily by blue light than by longer wavelengths of visible light." Abstract
Recent Studies on Photodamage to the Eye with Special Reference to Clinical and
Therapeutic Procedures. Photodermatology Photoimmunology and Photomedicine 1990; 7:98-105
U.P. Andley, and L.T. Chylack Jr.
"The effectiveness of light in inducing photodamage to the retina increases with decreasing wavelength from 500 to 400 nm."
"It is now well established that photoretinopathy is a cumulative process, and chronic light damage may be one of the factors contributing to the development ofage-related macular degeneration (AMRD)." Abstract
Note: more recent references on the risk of eye damage from light therapy can be found in the section marked - For Therapists