PART II - Information on Light Exposure and AMD

Age-Related Macular Degeneration (AMD) is the leading cause of blindness in North America.  Repeated exposure to high levels of light combined with the deterioration of anti-oxidative protective mechanisms that occurs with age contribute to the development of oxidative debris within the retina and in the region immediately adjacent to it.  AMD results from the accumulation of this oxidative debris which is itself phototoxic. Some investigators link the development of AMD with the levels of visible light exposure for at least the twenty year period before symptoms emerge. More recently, evidence indicates that increasing daily exposure to blue visible light of young adults may advance the onset of AMD by 10 years.

Exposure to bright light can overpower the protective anti-oxidative mechanisms in the retina.  Excessive light exposure induces the formation of lipofuscin, the oxidative debris that develops within retinal cells, and drusen, the oxidative debris that forms in the extra-cellular space between the monolayer of cells in the retinal pigment epithelium (RPE) and Bruch’s membrane. Bruch’s membrane is a membrane barrier adjacent to the RPE that separates the retina from the blood vessels that service the retina.

Drusen is a photo-oxidative by-product that accumulates between the retinal pigment epithelium and Bruch's membrane. Drusen formation is an early indication of AMD.  Drusen and lipofuscin contain phototoxic chromophores that generate radical oxygen species (ROS) when they absorb the blue wavelengths in visible light. These ROS induce additional damage by destroying photoreceptor and RPE cells, and attacking the integrity of the Bruch’s membrane. This "blue light hazard" is compounded in the aged eye because in humans the anti-oxidative protective mechanisms start to deteriorate at about age 40. 

Photoreceptor cells and cells of the RPE are not replicated after birth. It is therefore inevitable that there is a build up of oxidative debris within these cells which are exposed to high levels of light energy and high concentrations of oxygen, have high concentrations of polyunsaturated fatty acids which are extremely susceptible to peroxidation, and contain a number of potential photosensitizers. 

While "Bright Light" therapy has only been widely used for about ten years and its connection to AMD remains unproven, the accumulation of phototoxic debris from oxidative damage combined with the diminishing capability of anti-oxidative mechanisms that occurs with age is instrumental in the initiation of the damage to retinal tissues that leads to photoreceptor cell death and AMD. Recently, the molecular pathways by which light-induced oxidative damage produces the drusen which leads to AMD has been described. This establishes the connection between the repetitious insults to the retina from damaging levels of visible light exposure and the development of AMD.

The comfortable glow from a Sunnex Lo-LIGHT lamp makes light therapy safe for anyone who can tolerate normal indoor lighting.

FOR THERAPISTS AND EYE SAFETY EXPERTS: A MORE TECHNICAL AND COMPLETE DISCUSSION OF THE ROLE OF LIGHT IN THE PATHOGENESIS OF AMD please click Blue Light and AMD)