Nearly 12 million Americans have vision loss preventing them from seeing properly. Even the most accurate eyeglasses or contact lenses don't help enough. Although the loss of vision is a very significant problem, there is often help available. Many people with a visual impairment are able to resume many of their daily activities, drive, and maintain their independence as a result of low vision care.
What is Low Vision?
Low vision is an optometric specialty dealing with the examination and optical treatment of patients with significant vision loss. Many patients with vision loss cannot achieve their full potential with ordinary eyeglasses. In low vision telescopes, microscopic lenses, magnifiers, electro-optical systems and other sophisticated optical devices are used to enhance sight by magnifying the image on the retina of patients with partial sight. The right device can help people see better.
Generally the loss of vision happens slowly. Your eyeglasses or contact lenses don't seem strong enough. You find yourself straining to see things. A stronger prescription doesn't help. Loss of vision effects an estimated 3 million Americans each year. If you notice these behaviors a comprehensive low vision examination is necessary. There are many causes of vision loss including genetic, accidents, disease, and deterioration. Each of these can damage the eyes or other parts of the visual system.
What is Involved in Low Vision Care?
The process begins with a comprehensive eye examination by Dr. Politzer. This gathers information about your eye health, visual status, and the need for low vision care. If you are a candidate for low vision care, a low vision evaluation will then be scheduled.
In the low vision evaluation, your specific needs and goals are reviewed in depth. A variety of optical devices will be evaluated to assist in obtaining your needs and goals. High power reading glasses (microscopes), distance magnification systems (telescopes), hybrid devices (telemicroscopes), magnifiers, special filters, and electro-optical systems will be evaluated.
Your key to success is not only having the right optical devices, but also, and just as important, is training in the use of your prescribed low vision devices. The greater your needs, such as driving, the greater the training required.
Low Vision Exams
During a low-vision exam, we will you for a complete personal and family-general health and eye history. In addition, we will concentrate on your visual difficulties, asking about how the visual impairment is affecting your daily activities, computer use, reading, traveling, ability to recognize faces, functioning in the kitchen, driving, working, television viewing, attending school and participating in hobbies. We will perform specialized refraction and thoroughly examine each eye. In addition, we will measure your visual acuity using special low-vision test charts. These charts include a larger range of letters or numbers to more accurately determine the level of vision impairment. We will also evaluate your visual fields, investigate glare, contrast sensitivity and reading ability. At the conclusion of the evaluation, we will create a comprehensive, individual rehabilitation plan based on your visual abilities and goals. The vision rehabilitation will often happen over several visits to the clinic.
Causes of Low Vision
Low vision care helps people who have suffered a partial loss of sight. It is often a loss of visual acuity (clarity of sight), but may also be a loss of peripheral or extreme difficulty with light or glare. A visual impairment exists when functional vision cannot be adequately corrected with eyeglasses, contact lenses, medications, or surgery. Low vision services do not cure the cause of vision loss, but can help maximize the remaining vision to its fullest potential. Low vision care does not replace the need for other treatments such as surgery or medical care.
Common causes of low vision include:
Vision loss from stroke, head injury, or tumor
Histoplasmosis and Toxoplasmosis
Low Vision Devices
Telescopes are used to help distance vision. They may be mounted to a spectacle prescription so the patient can alternate vision from the telescope to the carrier (regular portion) of the lens. Telescopes provide magnification for improved detailed vision, but reduce peripheral field of vision. They are used as spotting devices and are not intended for full time continuous vision.
Microscopes are used to help near vision. They provide good magnification and a relatively large field of view. They are worn like glasses and do not rely on hand/arm strength or dexterity. They require a very close working distance to the object of regard, sometimes just a couple of inches.
Magnifiers are used to help mid-range and near vision. They may be stand mounted, hand held, or a combination. They come in a variety of sizes, shapes, and weights. Some are available with lighting built in. They give less magnification and have a smaller field of view than microscopes, but have longer (near normal) working distance.
Electro-optical systems are used to help reading. They are stand or tabletop mounted. Reading material is placed on a slide, which goes under a scanner that magnifies the image onto a monitor. They provide excellent magnification, contrast and working distance, but are fixed (non-mobile) and have a relatively small field of image view.
Macular degeneration is a disruption of the center spot of the retina, called the macula. The macula, smaller than a capital A, contains a concentrated layer of light sensitive cells called cones. It is the only area in the eye capable of 20/20 vision. It allows us to see faces, and to read and perform other fine vision tasks. Macular degeneration is the single largest cause of legal blindness in patients over 55 years of age. Juvenile forms of macular degeneration or dystrophies include Stargardt's Disease and Best's Disease. Most patients suffer from age related macular degeneration. Nearly 6% of people between age 65 and 74 may have macular degeneration and between age 75 and 84 about 20% have macular degeneration. There are two types of age related macular degeneration. They are often referred to as wet (neovascular) or dry (atrophic) macular degeneration. Wet macular degeneration may result in more severe loss of vision but in progression may be slowed with laser treatments if detected early. Dry degeneration is more common accounting for nearly 90% of age related macular degeneration. There is no proven cure of dry macular degeneration. Nutritional therapies, electro-stimulation, medications, surgeries to relocate the macula, and implantation of electronic chips are all under study at this time. None are yet proven but many hold hope for future treatment of this disease. Macular degeneration may result in a constellation of visual problems.