What is Low Vision?
Low vision is the term used to refer to a visual impairment that is not correctable through surgery, pharmaceuticals, glasses or contact lenses. It is often characterized by partial sight, such as blurred vision, blind spots or tunnel vision, but also includes legal blindness.
What causes Low Vision?
Some of the most common visual impairments that can cause low vision include the following:
Age-Related Macular Degeneration (AMD/ARMD): AMD is a leading cause of vision loss among Americans over age 60. It accounts for nearly half of all low vision cases. It is caused when the part of the eye responsible for sharp, straight-on vision – the macula – breaks down and causes a loss of central vision. There are two types of AMD, wet and dry. Wet AMD is caused by the growth of abnormal blood vessels under the macula. Central vision loss occurs rapidly with wet AMD. In dry AMD, light-sensitive cells in the macula slowly break down, leading to a gradual loss of central vision.
Diabetic Retinopathy: According to the National Eye Institute, more than 30 percent of Americans diagnosed with diabetes have some form of diabetic retinopathy. It is a major cause of blindness and is directly related to high blood sugar, which damages blood vessels. That damage affects the retina and can even lead to its detachment.
Glaucoma: Glaucoma is the second leading cause of blindness. With glaucoma, portions of vision are lost over time, usually with no warning signs or symptoms prior to vision deterioration. For many, a decrease in peripheral vision is the first sign of glaucoma.
Cataracts: Over 20 million people in the US alone have cataracts according to Prevent Blindness America. It appears as a clouding of the lens of the eye.
Retinitis Pigmentosa: This is a group of inherited diseases affecting the retina resulting in progressive vision loss. This type of vision impairment often begins in childhood with poor night vision and progresses over time.
There are also many additional causes of low vision, including strokes, TBI (traumatic brain injury) and other diseases common among a wider age range such as Stargardt’s maculopathy, albinism, ROP (retinopathy of prematurity), among others.
What is the difference between Low Vision and Legal Blindness?
Legal blindness" is a definition used by the United States government to determine eligibility for vocational training, rehabilitation,
schooling, disability benefits, low vision devices, and tax exemption programs. It's not a functional low vision definition and doesn't tell us very much at all about what a person can and cannot see.
Part 1 of the U.S. definition of legal blindness states this about visual acuity:
A visual acuity of 20/200 or less in the better-seeing eye with best conventional correction (meaning with regular glasses or contact lenses).
This is a 20/200 visual acuity measurement, correlated with the Snellen Eye Chart (pictured above):
If you can only read line 1 (the big "E") from 20 feet away while wearing your regular glasses or contact lenses, the doctor records your vision (or visual acuity) as 20/200 with best correction.
Update: In 2007, the Social Security Administration updated the criteria for measuring legal blindness when using newer low vision test charts with lines that can measure visual acuity between 20/100 and 20/200. Under the new criteria, if a person's visual acuity is measured with one of the newer charts, and they cannot read any of the letters on the 20/100 line, they will qualify as legally blind, based on a visual acuity of 20/200 or less.
Part 2 of the U.S. definition of legal blindness states this about visual field:
OR a visual field (the total area an individual can see without moving the eyes from side to side) of 20 degrees or less (also called tunnel vision) in the better-seeing eye.
What is Low Vision Care?
Some doctors of optometry specialize in low-vision rehabilitation. They examine, treat and manage the care of patients with visual impairments that can't be fully treated by medical, surgical or conventional eyewear or contact lenses.
Each type of low-vision problem requires a different therapeutic approach. After the optometrist conducts a thorough examination, which will also include tests to determine the patient's current vision status, the optometrist develops a treatment plan.
Treatment plans aim to maximize visual functioning so the patient can comfortably conduct his or her daily activities. The treatment plan may include prescription of glasses, specialized optical systems, therapeutic filters, non-optical options, video magnification or rehabilitation therapy. The optometrist may also prescribe therapy to enhance remaining visual skills and may refer the patient to other vision rehabilitation professionals, as necessary.
What are Low Vision Devices?
Low vision optical devices include a variety of devices, such as stand and hand-held magnifiers, strong magnifying reading glasses, loupes, and small telescopes. Because these devices can provide greatly increased magnification powers and prescription strengths, along with higher-quality optics (i.e., the way the lens bends or refracts light), they are different from regular glasses and commercially available magnifiers.
Low vision optical devices are task-specific. You can think of them as being similar to "tools" that are used to build a house—different tools for different tasks. Therefore, your eye doctor may prescribe several different low vision optical devices for various tasks: One or two devices for reading, another for watching television and seeing faces, another for seeing the computer screen, and yet another for sewing. Your doctor may also recommend sunglasses to reduce glare, protect your eyes from ultraviolet (UV) and blue light, and enhance your ability to see more clearly in different lighting conditions.
If you have low vision, your standard prescription eyeglasses are usually no longer sufficient to help with distance and near tasks. In addition, you may need several different optical devices to help with a variety of everyday tasks you want to do.
You may find that using low vision optical devices effectively is different from what you have been used to in the past, when a single pair of glasses did everything—helping you to see at distance, intermediate, and up close. Many persons with low vision can have 4-5 different devices to help with a range of everyday tasks.
Will Telescopic glasses allow me to drive?
It must be understood, that driving is a privilege and not a right and each state has specific laws which outline the legal requirements for driving. In California, the current Motor vehicle code VC 12805b states: The department shall not issue a driver's license to, or renew a driver's license of, any person:
(a) Who is not of legal age to receive a driver's license.
(b) Whose best corrected visual acuity is 20/200 or worse in that person's better eye, as verified by an optometrist or ophthalmologist. No person may use a bioptic telescopic or similar lens to meet the 20/200 visual acuity standards.
The screening criteria performed at the local DMV office is set at a 20/40 level. Thus anyone tested whose vision is poorer than 20/40, but better than 20/200 in the better eye, would fail the screening test, BUT, may still be legal to drive according to law in certain cases. Please ask about your specific needs.
The bioptic telescopic lens does not make one legal. It is not required to be fit for a low vision driver. The telescopic lens or bioptic is not used continuously while driving and you may be testing in your proficiency to drive with the bioptic if you elect to be fitted with the specialized low vision device. Please feel free to discuss your individual needs with us.
Will “Stronger Glasses” Help Me?
Maybe, however one must understand that conventional glasses are used to correct what is termed a “refractive problems – nearsightedness, farsightedness, and astigmatism. When an individual wears conventional glasses, objects appear clearly focused and in their natural size. Magnifiers however make objects larger and therefore easier to see. Magnification comes with its benefits but is often achieved with trade-offs. Magnification produced by stronger lenses only means holding things closer to see, and a problem with the extent of how much is seen at one time (seeing the bark on the tree without knowing you are in a forest!). Only enough magnification to accomplish a specific visual task is what is recommended. This is the goal of the low vision exam to select a right device for a specific visual task.