Radiation burns are caused by light and ocular radiation burns from ultraviolet rays, infrared rays, x-rays, microwaves, laser beams, and gamma rays.
Burns caused by ultraviolet rays include snow blindness, welders’ flash, and sun-lamp injuries. Ultraviolet waves do not penetrate the globe and, therefore, can deliver a burn to the cornea. Symptoms of these burns are usually delayed two to nine hours and include extreme pain, a sensation of sand in the eyes, and severe light sensitivity. The burns heal themselves within two or three days, but antibiotic or steroid drops may be prescribed. Ultraviolet burns can be prevented by wearing protective eyeglasses or goggles.
Eclipse blindness is an ultraviolet burn caused by watching the sun during an eclipse. Although the ultraviolet rays of the sun do not enter the globe of the eye, the heat generated within the eye during prolonged exposure produces a burn to the macula. The damage to the macula from an eclipse burn is irreversible and causes loss of central vision. An eclipse cannot be safely viewed directly or with the use of sunglasses, photographic film, or film negatives. An eclipse can be safely viewed indirectly by observing the image of the sun projected onto a flat surface through a small hole in a piece of paper.
Infrared rays can penetrate the eye and may cause cataracts. In the past, ocular infrared burns were found among steel workers and glass blowers. The adoption of safety goggles and eyeshields has virtually eliminated the problem.
X-rays may produce cataracts in threshold doses of approximately 1,000 rad, but may vary with exposure times. Simple dental or diagnostic x-rays will not endanger the eyes. X-rays used therapeutically to treat lesions near the eyes should be given only when the eyes are appropriately shielded.
Microwaves may cause cataracts but only when the eye is in the direct line of the beam. According to current knowledge, microwave ovens constitute no threat to vision.
Lasers are intense beams of light that can enter the globe of the eye. They are used therapeutically in ophthalmology to heal hemorrhages in the retina. The beam is focused directly onto the point of therapy that is exposed to the light for a specific amount of time. Industrial lasers can produce retinal burns when viewed directly or by reflection off other objects.
Gamma rays can produce cataracts and loss of vision. The rays released by atomic bomb explosions resulted in mass amounts of cataract cases following the bombings of Hiroshima and Nagasaki during World War II.