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VISION

What Is Low Vision?

Low vision is a loss of eyesight that makes everyday tasks a challenge. A person with low vision may find it difficult or impossible to accomplish activities such as reading, writing, watching television, recognizing a face or driving a car. When vision cannot be improved with regular eyeglasses, medicine or surgery, people with low vision need help to learn how to make the most of their remaining sight and keep their independence.

Vision Patterns and Vision Loss

  • Central vision

This is the detailed vision we use when we look directly at something. Macular degeneration (AMD) affects central vision. Diabetic retinopathy can affect central or peripheral vision.

  • Peripheral vision

This is the less detailed vision we use to see everything around the edges. Glaucoma affects peripheral vision first. Strokes can affect one side of the peripheral vision.

  • Contrast sensitivity

This is the ability to distinguish between objects of similar tones like milk in a white cup or to distinguish facial features. All eye problems can decrease contrast sensitivity.

  • Depth perception

This is the ability to judge the position of objects. New vision loss in one eye can affect depth perception, such as the height of a step.

  • Visual processing

The lens in our eye focuses light rays onto our retina. The retina converts these light rays into signals that are sent through the optic nerve to our brain, where they are interpreted as the images we see. A problem with any of these processes affects our vision in various ways.

Many other medical conditions can effect your vision.

For more Low Vision resources visit

IALVS.com

California DMV Bioptic Requirements

Bioptics are allowed for driving.

The California rules are vague, but California has licensed biotic drivers for many years.

  • Visual Acuity: A driving license will not be issued to a driver 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 telescope or similar lenses to meet the 20/200 visual acuity standards. 

 

A new pilot program in Northern California provides additional assessment tools. This includes any observation of physical limitations that could affect safe driving, and a cognitive exercise that will require you to recall in writing your social security number or your zip code if you have never been issued a SSN. If you fail to perform well on the standard tests or new assessments tools, contrast sensitivity and a Perceptual Response test will be performed.

Last Reviewed July 2009

Causes of Vision Loss

Some of the major causes of vision loss are age related macular degeneration, diabetic retinopathy, inoperable cataracts, and open angle glaucoma.

  • Macular Degeneration

Age related macular degeneration is the leading cause of vision loss in those over 65. By definition, macular degeneration affects only the macular portion of the retina. The retina, like film in a camera, is the photosensitive layer of the eye. It is “wall-papered” to the back of the eye and is extremely thin. The macular portion of the retina, a very small area, is the part we use for sharp, clear central detail vision. The rest of the retina, the peripheral or side vision retina, is used for mobility and detecting motion.

When the macula degenerates, whether it’s wet or dry, only the central vision is reduced. The side vision always remains. Always.

  • Diabetic Retinopathy

Diabetic retinopathy is a leading cause of blindness in American adults. It is caused by changes in the blood vessels of the retina. In people with diabetes for many years, blood vessels may swell and leak fluid or abnormal new blood vessels grow on the surface of the retina. If you have diabetic retinopathy, at first you may not notice changes to your vision. But over time, diabetic retinopathy can get worse and cause vision loss. Diabetic retinopathy usually affects both eyes.

  • Cataracts

A cataract is a clouding of the normal crystalline lens located in the eye. Most cataracts are related to aging and are very common in older people. By age 80, more than half of all Americans either have a cataract or have had cataract surgery. A cataract can occur in either or both eyes, but cannot spread from one eye to the other.

Treatment is by surgical extraction of the lens with replacement of a plastic implant. For the most part, cataract surgery is extremely successful and results in virtually normal vision. However, there are times when cataract extraction can exacerbate macular degeneration or cause macular edema resulting in increased vision loss.

  • Glaucoma

Glaucoma is actually a group of diseases that can damage the eye’s optic nerve resulting in vision loss and even blindness. Glaucoma occurs when the normal fluid pressure inside the eyes slowly rises. Usually there are no symptoms, which is why glaucoma is called the silent thief of sight. However, with early treatment, you can often protect your eyes against serious vision loss.

There are many types of glaucoma including open angle, closed angle, congenital, and secondary. The most common type, open angle, has no symptoms. There is no pain, redness, swelling, tearing or other signal to tell you of the problem. The vision loss is so gradual, beginning in the periphery or in the normal blind spot that people do not notice until significant loss occurs.

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