Formula Medical Group
Apple Valley, CA

James Krider, MD

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Blind spots

What are blind spots?

A blind spot is a distortion or absence of sight in a small portion of the visual field. Blind spots that completely eradicate vision are called negative scotomas, while spots that look like steady or flashing lights are called positive scotomas. These spots often go unnoticed unless they interfere significantly with vision.

What causes blind spots?

A wide range of medical problems can lead to the development of blind spots.

Among the most common causes are glaucoma, in which abnormally high fluid pressure builds up inside the eye, and diabetic retinopathy, in which blood vessels in the retina overgrow and burst after a long history of diabetes. Macular degeneration, a deterioration of part of the retina, causes blind spots in the central part of the field of vision; distortion of straight lines is an early sign of the disorder. Atherosclerosis (the buildup of fatty deposits inside arteries) in the artery that feeds the retina can cause a blind spot as well. Strokes, also caused by atherosclerosis, sometimes manifest themselves as blind spots, but other stroke symptoms almost always accompany the visual disturbance. Migraine headaches cause temporary blind spots. Alcohol abuse, multiple sclerosis, and pituitary tumors may also result in blind spots.

How are blind spots diagnosed and treated?

Diagnosis is based on an eye examination and other tests. If an eye hemorrhage is the cause of a blind spot, the doctor will be able to see it using an ophthalmoscope — a hand-

ophthalmoscope — a hand-held magnifying instrument with

Diabetes often produces eye complications such as bursting of blood vessels.

held magnifying instrument with a lighted tip. Blind spots resulting from nerve defects may require careful vision testing aimed at locating exactly where the blind spot is situated in the field of vision. By thus locating a blind spot, the doctor will obtain clues about the cause.

Treatment varies widely depending upon the cause. Blind spots themselves are not treated, but when the disease that is responsible for their development is under control, they will usually disappear or stop progressing. Eye drops or oral medications can control glaucoma, for instance, and diabetic retinopathy can often be kept in check with laser treatments to stop the bleeding.

What can I do myself?
Self-treatment of blind spots is not effective.

Atherosclerosis can cause fatty deposits and tiny hemorrhages in the eye.

When should I see my doctor?
If blind spots or other visual disturbances develop, a doctor or eye-care professional should be seen promptly This is especially important for persons with diabetes or glaucoma.

What will the doctor do?
The doctor will take a complete medical history, with special attention to any underlying conditions that might be causing blind spots. The patient may be referred to an ophthalmologist (a physician who specializes in treating eye diseases) for a thorough eye examination. A procedure called tonometry (in which a puff of air is blown into the eyeball) can determine whether glaucoma is present. More sophisticated tests may be necessary to rule out other causes such as a pituitary tumor.

The course of blind spots

Blind spots may disappear on their own. Scotomas due to migraine headaches go away when the headache dissipates. If blind spots are due to other diseases, they may persist and be accompanied by other symptoms.

Are blind spots dangerous?
They may make it unsafe to drive or use machinery, and they can indicate the presence of a more serious medical problem.

What can I do to avoid blind spots?

  • Have your eyes checked regularly.
  • Anyone who has diabetes should learn how to keep the disease under control.
  • To prevent atherosclerosis, eat a low-fat diet, exercise regularly, and have blood cholesterol levels checked routinely. The same measures, along with control of high blood pressure, will reduce the risk of stroke.
  • At the first sign of a migraine headache, take a pain reliever such as aspirin, apply a cold cloth to the head, and lie down for several hours.
  • Avoid excessive alcohol.
  • Among the symptoms of an impending stroke are a sudden, temporary weakness or numbness on one side of the body, temporary loss of speech, or trouble understanding speech. Associated visual disturbances may include blind spots and temporary dimness or loss of vision. This is a medical emergency; anyone with these symptoms should get to the nearest hospital emergency room at once.
  • Blind spots due to a migraine headache may be accompanied by double vision, a headache that radiates to the eye, nausea, vomiting, dizziness, and sensitivity to light.
  • If glaucoma is present, rainbows may appear around lights, vision may be blurred, the forehead or brow may ache, and the pupils may be dilated.
  • In diabetic retinopathy, tiny red dots may appear on the retina due to bleeding (pinpoint hemorrhages). Larger hemorrhages may follow, leading to loss of vision.
  • In atherosclerosis, deposits of fat and cholesterol build up on the walls of the arteries, slowing the blood flow and setting the stage for a heart attack or stroke. Usually there are no symptoms, but regular cholesterol tests will reveal any problem.
This article was last reviewed November 21, 2005 by Dr. James Krider.
Reproduced in part with permission of Home Health Handbook.
Macular degeneration

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