The products of these reactions impair the cells' ability to respond to light and in extreme cases can destroy them. Depending on the severity of the damage, an affected observer experiences either a temporary or permanent loss of visual funnction. This photochemical injury occurs mainly when the retina is exposed to blue and green light. When longer wavelengths of visible light and near-infrared radiation pass into the eye, they are absorbed by the dark pigment epithelium below the retina. The energy is converted into heat that can literally cook the exposed tissue.
Photocoagulation destroys the rods and cones, leaving a permanently blind area in the retina.
This thermal damage also occurs during extended exposure to blue and green light. Both photochemical and thermal retinal injuries occur without the victim's knowledge, as there are no pain receptors in the retina and the visual effects do not occur for at least several hours after the damage is done. Jerusalem - Palestine.