The Reasons Why People Have Bad Eyesight

Many reasons exist for bad vision. In adults and children, development of cataracts causes a large amount of vision loss. However, other diseases not specifically about the eye still contribute to bad eyesight, such as multiple sclerosis or diabetes. In general, most people do not have 20/20 vision, which is perfect, but they have nearsightedness, the ability to see closer, or farsightedness, the ability to see far away. Vision loss also results from hereditary history of eye conditions, so if your parents wear glasses, then more than likely, you went shopping for glasses at a young age. More serious diseases severely manipulate the eye's ability to interpret images.

Glaucoma

• Diseases of the eye tend to create vision loss over time, either very slowly or rapidly. Persons over 60 tend to experience glaucoma, a gradual loss of eyesight that occurs as cells in the optic nerve grow weaker. In many cases, glaucoma results from a failure of the eye to drain fluids properly, which causes a pressure to build up. Risk factors for glaucoma increase for individuals who are older, of African or Hispanic descent, and long-term smokers or steroid users. Genetics also plays a part in the likelihood of contracting glaucoma.

Age-Related Macular Degeneration

• The macula is responsible for central field of vision. If you notice a distortion of images, decreased color association or a darkened area in the center of images, then you experience the symptoms of age-related macular degeneration or AMD. As the macula is responsible for photosensitive cells and the majority of your eyesight, AMD is the leading cause of blindness, according to John Shoemaker of Prevent Blindness America. The disease comes in two forms, called either "wet" or "dry" AMD. In dry AMD, small yellow fat deposits develop under the macula. Wet AMD comes from blood vessel growth that leak into the macula, which causes vision distortion and scare tissue formation.

Optic Nerve Atrophy

• Tissue damage in the optic nerve creates either partial or almost full vision loss for the sufferer. Optic nerve atrophy (ONA) associates to various diseases, including ischemic optic neuropathy, which impacts older persons. Another type of ONA is arteric optic neuropathy, a result from poor blood flow to the optic nerve. Diseases related to the cause of ONA include multiple sclerosis, brain tumor and stroke, according to MedlinePlus. Gradually, ONA continues to worsen until the pupil stops reacting to light.

Cataracts

• Older adults experience cataracts, a clouding of the eye lens. As light enters the eye, the visual image blurs as the light diffuses inside the eye. Later, the eye lens becomes tinted brown and green, creating further problems for light to pass through the eye. Symptoms for cataracts are light sensitivity, double vision, fading or yellowing of colors and blurred vision. Night vision is the ability most affected to those suffering from cataracts, as the amount of light decreases to the eye. Though most cataracts result from older age, secondary cataracts form as a result of glaucoma or diabetes. Congenital cataracts cause blindness in children. Others experience cataracts from use of corticosteroids, excessive consumption of alcohol, smoking and long-term exposure to sunlight.

Other Bad Eyesight Factors

• If your parents wear glasses, then, most likely, you developed the same eye condition. However, sitting too close to the television or crossing your eyes are myths of vision loss, since no evidence supports the theory that either causes bad eyesight. Staring at the computer screen or video game also does not cause vision loss, but the eye tends to dry out from a loss of blinking, which causes fatigue and eyestrain.