Blindness

Night blindness is poor vision at night or in dim light.

Nyctanopia; Nyctalopia; Night blindness

Night blindness may cause problems with driving in the evening or at night. People with night blindness often have trouble seeing the stars on a clear night.

• Birth defects
• Cataracts
• Retinitis pigmentosa
• Use of certain drugs
• Vitamin A deficiency

In some cases, the eyes may simply have trouble adapting to darkness. The problem may not be due to another medical condition. However, it is often linked to myopia(nearsightedness).

Take safety measures to prevent accidents in the areas of low light. Avoid driving a car at night.

Vitamin A supplements may be helpful.

It is important to have a complete eye exam to determine the cause, which may be treatable. Call your eye doctor if symptoms of night blindness persist or significantly affect your life.

Your health care provider will examine you and your eyes. The goal of the medical exam is to determine if the problem can be corrected (for example, with new glasses or cataract removal), or if the problem is due to something more serious.

The doctor may ask you questions, including:

• When did the night blindness begin?
• Did it occur suddenly or gradually?
• Does it happen all the time or just sometimes?
• How severe is the night blindness?
• Are you nearsighted?
• Do you have other vision changes?
• What other symptoms do you have?
• Do you have unusual stress, anxiety, or a fear of the dark?
• Does use of corrective lenses improve night vision?
• What medications do you use?
• How is your diet?
• Have you recently injured your eyes or head?
• Do you have a family history of diabetes?

A slit lamp examination may be done.

Blindness is a lack of vision. It may also refer to a loss of vision that cannot be corrected with glasses or contact lenses.

• Partial blindness means you have very limited vision.
• Complete blindness means you cannot see anything and do not see light. (Most people who use the term "blindness" mean complete blindness.)

People with vision worse than 20/200 are considered legally blind in most states in the United States.

Vision loss refers to the partial or complete loss of vision. This vision loss may happen suddenly or over a period of time.

Some types of vision loss never lead to complete blindness.

Loss of vision; No light perception (NLP); Low vision; Vision loss and blindness

Blindness has many causes. In the United States, the leading causes are:

• Accidents or injuries to the surface of the eye (such as chemical burns or sports injuries)
• Diabetes
• Glaucoma
• Macular degeneration

The type of partial vision loss may differ, depending on the cause:

• With cataracts, vision may be cloudy or fuzzy, and there may be problems seeing shapes
• With diabetes, vision may be blurred, there may be shadows or missing areas of vision, and difficulty seeing at night
• With glaucoma, there may be tunnel vision and blurry vision
• With macular degeneration, the side vision is normal but the central vision is slowly lost

Other causes include:

• Blocked blood vessels
• Complications of premature birth (retrolental fibroplasia)
• Complications of eye surgery
• Lazy eye
• Optic neuritis
• Stroke
• Retinitis pigmentosa
• Tumors such as retinoblastoma and optic glioma

The kind of home assistance you need will depend on your type of vision loss. It is important for a blind person to be able to dress, eat, function independently, and stay safe.

Many services are available that provide the training and support blind people need to function independently.

Ideas to keep things organized at home:

• Always keep certain items in the same drawer, cabinet, table, or counter space.
• Learn to recognize the shape of certain items, such as egg containers or cereal boxes.
• Use plastic rings to hold pairs of socks together, whether you are washing, drying, or storing them.
• Use small Braille labels, including a simple form of Braille called uncontracted Braille.
• Use small raised dots, rubber bands, Velcro, or colored tape to label items that are hard to read.
• Use caulking, raised rubber, or plastic dots to mark the "on," "bake," and certain temperature settings on the furnace thermostat and dials on stoves, toasters, the washer, and dryer.
• Use a phone with large numbers and memorize the keypad.
• Fold different types of paper money in a different way. For example, you can fold a $10 bill in half or double fold a $20 bill.
• Use Braille or large-print checks.

Tips to help you get around and stay safe at home:

• If possible, learn to use a long white cane to help you get around on your own.
• When walking with someone else's help, grasp their arm just above the elbow. Walk slightly behind them to follow their motions.
• Remove lose wires or cords from the floor.
• Remove loose throw rugs.
• Do not keep small pets in your home.
• Fix any uneven flooring in doorways.
• Have good lighting.
• Put hand rails in the bathtub or shower and next to the toilet.
• Place a slip-proof mat in the bathtub or shower.

A number of different low-vision aids can help:

• Magnifiers
• Technology aids to make it easier to use cell phones and computers
• Watches made for people with low vision, or talking watches and clocks

Sudden vision loss is always an emergency, even if you have not completely lost all vision. You should never ignore loss of vision, thinking it will get better.

Contact an ophthalmologist or go to the emergency room immediately. Most serious forms of vision loss are painless, and the absence of pain in no way diminishes the urgent need to get medical care. Many forms of vision loss only give you a short amount of time to be successfully treated.

A complete and thorough eye examination will be performed. The treatment will depend on the cause of the vision loss.

For long-term vision loss, see a low-vision specialist, who can help you learn to care for yourself and live a full life.

Kraut JA. Vision rehabilitation. In: Tasman W, Jaeger Ea, eds. Duane's Ophthalmology. 15th ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2009:chap 46.

Olitsky SE, Hug D, Smith LP. Disorders of Vision. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 18th ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 620.

Sterns GK, McCormick GJ. Ophthalmologic disorders. In: Duthie EH, Katz PR, Malone ML, eds. Practice of Geriatrics. 4th ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 24.

Review Date: 07/28/2010

Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington School of Medicine; and Franklin W. Lusby, MD, Ophthalmologist, Lusby Vision Institute, La Jolla, California. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

According to Horseman Magazine, some horse owners may opt for surgery. This however is not always a practical solution. If the condition is still in its early stages, your horse may do well with medication. Some medicines that may be prescribed include antibiotics, banamine, steroids, bute and aspirin. Administering steroids however when there are eye ulcers may lead to blindness. Treatment option should be tailored according to the particular condition of the affected horse.

It is important to remember that moon blindness is a recurrent condition. Even if a horse's eye is back to normal, another future episode of moon blindness could happen. Succeeding episodes are more serious and more difficult to treat.

The Horse Protection Society of North Carolina (HPS) has experimented and found that horses treated for recurrent uveitis need 75,000 units beta carotene morning and evening for the rest of their lives. If you stop treatment, the recurrent uveitis may very well return.

Lutein is also of benefit to horse's eyes when given one gel cap in their feed. The gel caps are just dropped into the horse's feed morning and evening.

Some people swear by the Guardian Mask which is a revolutionary product specifically designed to help horses live normal productive lives with conditions such as uveitis, (moonblindness), headshaking, glaucoma, eye cancer, cataracts and eye injuries. With its unique patented design and UV-protective "eyes," it has proven to be the number one aid in treatment of these conditions and diseases, and, in numerous cases, without the additional use of medications or surgeries.