What Is Low Vision?
Low vision is a class of visual disabilities, which result in progressive loss of visual acuity and functionality and cannot be cured by medication, surgery or corrective lenses.
Low vision disorders include age-related macular degeneration (AMD), diabetic retinopathy, retinitis pigmentosa, glaucoma, and certain types of stroke-related vision disabilities.
Low vision is a growing problem. It strikes seniors more than any other age group.
As the U.S. population ages, we see more and more people affected by macular degeneration.
It now strikes someone new every three minutes in the U.S.
Low vision is the third leading cause of disability among seniors – ranking only behind heart disease and arthritis.
It is a major cause of falls leading to fractures, head injuries and hospitalizations.
It is also a significant cause of depression as it robs seniors of the opportunity to lead safe, independent and fulfilling lives.
It leads to enormous health care costs for the elderly.
The World Health Organization defines impaired vision in five categories:
- Low vision 1 is a best corrected visual acuity of 20/70.
- Low vision 2 starts at 20/200.
- Blindness 3 is below 20/400.
- Blindness 4 is worse than 5/300
- Blindness 5 is no light perception at all.
- A visual field between 5° and 10° (compared with a normal visual field of about 120°) goes into
category 3; less than 5° into category 4, even if the tiny spot of central vision is perfect.
Symptoms of low vision include difficulty recognizing objects at a distance, differentiating colors
(particularly in the green-blue-violet range), and seeing well up close (such as reading or cooking).
Those afflicted with low vision often cite difficulty recognizing faces of friends and relatives,
doing things around the house because lights seem dimmer, and matching colors of clothes.
Age-related macular degeneration affects 26% of those over 75 and, as mentioned, strikes one American
every three minutes.
The Effects of Low Vision
Most low vision diseases affect the macula, which is the part of the eye where central, or detail, vision
originates. Light reaches the macula where it is concentrated and passed via the optic nerve to the brain,
so images can be formed.
At the center of the macula is an area called the FOVEA. This is where the greatest number of cells are
concentrated. The fovea is the true focal point of detail vision.
Whenever light strikes the fovea, a waste product called drusen is formed. The healthy macula simply disposes of this waste naturally.
When macula degeneration strikes, this waste removal process is affected. Drusen builds up and begins to interfere with detail vision.
Moreover, this buildup begins to contaminate adjoining cells, so that the destruction of central vision progressively worsens.
Other than some recently developed, injectible drugs that reduce the bleeding associated with wet macular degeneration,
there is no cure for the macular damage caused by AMD.
There is, however, something that can be done about it. SightlineSM.
