National Geographic : 2016 Sep
Cornea Lens Ciliary body Zonules Iris Macula Retina Atrophic photoreceptors Accumulated deposit of debris Deteriorating cells Optic nerve Normal vision VITREOUS CAVITY Anterior chamber Choroid MANUEL CANALES, NGM STAFF; PATRICIA HEALY. PHOTO: DESIGN PICS INC, NATIONAL GEOGRAPHIC CREATIVE; MANIPULATIONS BY NGM STAFF SOURCES: VISION LOSS EXPERT GROUP; SILVIO PAOLO MARIOTTI, WORLD HEALTH ORGANIZATION; UNITED NATIONS DEVELOPMENT PROGRAMME Eyes Under Threat Multiple diseases can afflict the same eye. Three common and treatable diseases occur in the front of the eye. There currently is no cure for age-related macular degeneration, which occurs in the back of the eye near the retina. GLAUCOMA Glaucoma is caused by fluid buildup in the eye, resulting in pressure that can damage the optic nerve. If it’s caught early enough, surgery and medication may slow its advance. CATARACTS The world’s leading cause of blindness, cataracts are caused when proteins in the lens clump together, blocking and distorting light to the retina. Surgery can restore sight. REFRACTIVE ERRORS Nearsightedness, farsighted- ness, and astigmatism are types of refractive errors, flaws that keep the eye from focus- ing light sharply on the retina. Absent lenses or surgery, they’re the most common causes of impairment. AGE-RELATED MACULAR DEGENERATION Caused by an alteration of the underlying layers of the retina’s macular area, AMD affects photo- receptors that process images. There is no cure. The most common form of age-related macular degeneration, called atrophic or dry AMD, is caused by deposits of deteriorat- ing cells that cause the retina to atrophy.