What Is Vision Impairment?
Vision impairment and blindness can occur in varying degrees and affect an individual's ability to see light and form. Vision loss can be caused by the natural process of aging, genetic disorders, eye trauma, or disease.
A legally blind individual has visual impairment significant enough to make it unsafe to operate a motor vehicle. A legally blind individual has visual acuity of 20/200 or less even with the help of corrective lenses, while healthy vision is considered 20/20.
What is '20/20 vision'?
A person with 20/20 vision clearly sees an object from 20 feet away. A person with 20/40 (or higher) vision can see an object clearly at 20 feet what a normal person would see at 40 feet.
Conditions Impacting Vision:
Refractive Errors occur when the focusing of light by the eye reduces visual acuity. This type of vision impairment is caused by problems with the eye's physical optical ability (myopia or hyperopia) and/or altered eyeball shape (astigmatism).
Cataracts that cloud the lens of the eye are usually related to aging and more than half of Americans will experience a cataract or cataract surgery by 80 years of age. In some cases cataracts can form due to complications from diabetes, steroid use, trauma to the eye, or exposure to some types of radiation.
Cataracts can result in cloudy or blurry vision, glare from lights, faded appearance of colors, double vision, and poor night vision.
Macular Degeneration is usually age-related and the leading cause of vision loss in America, after age 60. The most common form is dry macular degeneration in which the cells in the macula (the part of the eye that sees fine detail) start to break down or die. This is not a condition that causes pain. The vision can abruptly worsen or can deteriorate so slowly that the individual does not notice the changes in vision. While it does not cause total blindness, macular degeneration can impact vision to the point of legal blindness.
Wet macular degeneration is an eye disease characterized by swelling of the blood vessels that causes leaking and is also associated with aging.
Diabetic Retinopathy is a complication of diabetes. There are two types:
- Nonproliferative, where blood vessels may swell or become blocked.
- Proliferative, when new blood vessels begin to grow in the retina.
Symptoms include gradual loss of vision, blurriness, missing areas of vision, and loss of night vision.
Glaucoma is caused by aqueous humor (the liquid in the eye) build up, resulting in pressure that damages the nerves in the eye. There are four types:
- Open angle (chronic) - the cause is unknown, but it tends to run in families, with people of African American descent at higher risk. This is the most common type, and occurs painlessly and slowly. Symptoms: loss of peripheral vision
- Angle closure (acute) - this type of glaucoma is an emergency condition. It is caused by a sudden blockage of the aqueous humor in the eye. Certain medicines and dilating eye drops may trigger this type of glaucoma, and once you have had this type of glaucoma in one eye, you are at risk of having it in the other eye.
Symptoms: sudden pain in the eye, cloudy or lessened vision, halos around lights, red eye, nausea and/or vomiting, redness of the eye
- Congenital glaucoma - this results from abnormal development of fluid channels in the eye, and is present at birth. Symptoms: enlargement of the eye, redness, tears, sensitivity to light, cloudy eye. Symptoms are usually noticed within a few months of birth.
- Secondary glaucoma is caused by certain classes of drugs and certain types of diseases, both systemic and eye diseases.
Retinitis Pigmentosa is an uncommon condition that involves damage to the retina (the tissue at the back of the inner eye). It can run in families or be caused by several genetic defects. Symptoms include decreased night vision, loss of peripheral vision, and, in advanced stages, loss of central vision.
Color Blindness can be genetic, due to physical trauma such as brain or retinal damage, or a side effect of macular degeneration. An individual who is color blind may have partial color blindness (the inability to see either red-green or blue-yellow) or total color blindness, in which all color looks gray. Color blindness is usually not considered to be a serious health concern.
A number of systemic diseases can cause vision impairment or blindness as a side effect.
Diagnosis of Vision Problems:
It is important to get regular eye exams from a qualified ophthalmologist, optometrist, or orthoptist. A general practitioner will sometimes perform the preliminary exam before providing a referral to an eye specialist.
Eye exams can consist of the following:
- Medical history
- Physical exam of the eye including eye muscle test and visual assessment of the eye tissues
- Visual acuity measurement (reading line of letters that are various sizes)
- Refraction assessment to assess how light flows through the eye
- Testing of peripheral vision
- Color vision test
- Slit-lamp exam
- Retinal exam (involving dilation of the pupils)
- Glaucoma test to measure pressure in the eye
Treatments for Vision Loss:
According to WHO, 80% of vision impairments can be treated or cured. Treatments can involve the following
- Corrective lenses
- Cataract surgery, which removes the clouded lens and replaces it with an intraocular lens
- Surgery to implant a telescopic lens in the eye (macular degeneration)
- Laser surgery/therapy
- Medication injected into the eye (macular degeneration)
- Photodynamic therapy in conjunction with medication (macular degeneration)
- Anti-oxidant vitamins and zinc can help prevent and slow the progression of macular degeneration
- Eye drops or oral medications (glaucoma)
- Drainage implants (glaucoma)
- Filtering surgery (glaucoma)
Research is still being conducted on the use of gene therapy but so far trials have shown promising results.
Aids for the Visually Impaired:
Whether the vision problem is treatable or not, there are many options to aid those with impaired eyesight in their normal daily life.
For those who are not suffering from total blindness, a Low Vision Specialist can be consulted to learn more about treatment and environmental adaptations for home and work.
- Physical enhancements to printed objects, such as large print, varying sizes for currency, or Braille
- Magnification tools
- Devices with audio notification
- Specialty pens with textured ink for labeling
- Specialty lighting
- Corrective lenses
- Guide animals
- Walking cane
Additional Resources for Blindness:
American Foundation for the Blind is a non-profit organization dedicated to broadening opportunities and services for the blind, as well as advocating for the visually impaired in public policy.
National Federation of the Blind is an advocacy and educational membership group for the blind with affiliates in all 50 of the United States.
Helping the Blind and Visually Impaired - Resources and information for vision impairment.
Living Blind provides a network of resources and information.
DeafBlind.com offers information for and about those dealing with blindness and hearing loss.
Stroke.org provides information about vision loss after a stroke.
Full Circle of Care has information on how to obtain financial assistance for the visually impaired.
The AMD Alliance is an international education and advocacy group for age-related macular degeneration. The site has extensive information to assist those who are adjusting to life after vision loss.