Guide Dogs for the Blind serves any person who is blind or visually impaired living in the United States or Canada desiring enhanced mobility, independence, community, and inclusion.
Blindness is a spectrum, and many of our clients have varying degrees of functional vision. According to the American Foundation for the Blind, it's estimated that only 18% of people who are visually impaired are totally blind. More often, it’s loss of central or peripheral vision, or spotted/blurred vision as the result of disease, injury to the eye, or an inherited or congenital condition. Even people who can’t see anything at all may have the ability to perceive some light.
Below are some examples of common types of vision loss and how they might affect someone's field of vision.
Central Vision Loss
This type of vision loss is caused by damage to the macula. According to the Macular Society:
"The macula is part of the retina at the back of the eye. It is only about 5mm across but is responsible for our central vision, most of our color vision, and the fine detail of what we see. A healthy macula is about 250 microns (one-quarter of a millimeter) thick. The macula has a very high concentration of photoreceptor cells – the cells that detect light. They send signals to the brain, which interprets them as images. The rest of the retina processes our peripheral, or side vision.
"Age-related macular degeneration is the most common condition, generally affecting people over the age of 55. A group of rare inherited conditions called macular dystrophies can affect much younger people. Some of these rare conditions can appear in childhood, although some are not diagnosed until later in life."
Peripheral Vision Loss (Tunnel Vision)
Diseases or injuries affecting other parts of the retina will obstruct the peripheral field of vision, sometimes constricting it so much that it is like viewing the world through a pinhole. Glaucoma and retinitis pigmentosa are two common eye diseases that can result in tunnel vision.
Glaucoma is a group of eye conditions that damage the optic nerve. The optic nerve sends visual information from your eye to your brain and is vital for good vision. Damage to the optic nerve is often related to high pressure in your eye. But glaucoma can happen even with normal eye pressure. Glaucoma can occur at any age but is more common in older adults. It is one of the leading causes of blindness for people over the age of 60. (Source: Mayo Clinic)
Retinitis pigmentosa (RP) is a group of rare eye diseases that affect the retina (the light-sensitive layer of tissue in the back of the eye). RP makes cells in the retina break down slowly over time, causing vision loss. RP is a genetic disease that people are born with. Symptoms usually start in childhood, and most people eventually lose most of their sight. (Source: National Eye Institute)
Various circumstances can affect the entire field of vision, producing symptoms that result in spotted, distorted, blurred or double vision. Diabetic retinopathy, retinopathy of prematurity, and injuries to the eye can cause such symptoms. These conditions may result in a random loss of a part of the visual field or in a loss of all of it, resulting in total blindness.
If you or someone you know is interested in learning more about GDB's free programs and services for people who are blind or visually impaired, please visit our Client Programs page today or contact our Support Center at 800.295.4050.