Millions of people have significant visual impairments that can make daily life challenging. Although many vision problems are readily treated with corrective lenses, treating low vision may not be so simple.
"Low vision" is a term used to describe the inability to see clearly. Even after correcting for vision with glasses or contact lenses, many people still cannot see well and test at lower than 20/40 vision. The American Academy of Opthalmology defines low vision as what happens if ordinary eyeglasses, contact lenses or intraocular lens implants do not provide a person with clear vision.
Anyone with reduced vision that is not corrected by some method of lenses or surgery is considered to have low vision or be visually impaired. Low vision may cause slight vision loss or even blindness.
Causes of low vision
There are many factors that contribute to the onset of low vision, including disease, aging, injury, and heredity. The following are some of the more common causes of low vision.
* Age-related macular degeneration (AMD): This is a common eye condition among people age 50 and older. In fact, it is the leading cause of vision loss in older adults, says the National Eye Institute. When a person has AMD, the macula, which is the most sensitive part of the retina responsible for fine-tuning images received by the eye, deteriorates and does not work properly. Though there might be some vision, images won't be clear. The most common form of age-related macular degeneration is known as nonexudative, or "dry" form. This generally causes vision loss that develops gradually. More rapid and severe vision loss comes from exudative, or the "wet" form, of macular degeneration. This occurs when abnormal blood vessels develop under the macula and leak fluid and blood.
* Cataracts: Cataracts are a clouding of the lens of the eye that usually develops with aging. It may be present at birth or be the result of an injury to the eye. Depending on the severity of the cloudiness of the lens, vision can be impacted greatly. Cataracts may form as a result of long-term exposure to ultraviolet light, exposure to ionizing radiation, secondary effects of diseases such as diabetes, hypertension and advanced age, or trauma.
* Glaucoma: When a person has glaucoma, eye damage occurs to his or her eye when there is a buildup of fluid pressure within the eye, also known as intraocular pressure. This pressure can damage the optic nerve and cause visual field loss, which over time might escalate to blindness. Glaucoma is often dubbed "the silent thief of sight," because in most cases it progresses slowly and vision loss is not immediately apparent.
* Diabetic retinopathy: Vision can fluctuate daily as a result of diabetes. Diabetic retinopathy can cause blood vessels in the retina to develop abnormal off-shoots that leak blood and interfere with vision, eventually causing severe damage to the retina.
* Retinal detachment: This occurs when the retina separates from its underlying layer. The portion that detaches may be rendered useless and cause total impairment of vision. Some retinas can be surgically reattached, and vision may be restored partially if surgery occurs promptly.
* Aniridia: Aniridia occurs when the iris, which is responsible for controlling the diameter and size of the pupils and regulating the amount of light reaching the retina, fails to develop normally. If the iris is not functioning properly, extreme sensitivity to light and an inability to see clearly may result.
Treatment for low vision
Treatment cannot begin until your vision is assessed by a professional. An optometrist may conduct various vision acuity tests to determine what might be the cause of vision loss. Each type of low vision problem requires a different approach to treatment, so it's important to correctly diagnose the problem before beginning treatment.
Some treatment options for low vision may include specialized optical systems, video magnification, therapeutic filters, or special prescription glasses. There also may be the need to perform eye exercises that help maximize existing visual function. Individuals may have to use a combination of devices to find the ones that help the best.
Only a doctor can determine the culprit behind vision loss. Routine visual exams are recommended at least every year and may need to be more frequent if a person is suffering from deteriorating vision. If caught early, many eye conditions can be managed to help prevent further loss of vision.