Blindness

What is blindness?

Blindness is the loss of vision, not correctable with lenses. Blindness may be partial, with loss of only part of the vision. It may also be complete, in which case there is no perception of light. People with vision worse than 20/200 (a person with 20/200 eyesight can clearly distinguish an object at 20 feet that a person with normal vision can clearly distinguish at 200 feet) or a field of vision of less than 20 degrees in the better eye are considered legally blind.

What are the causes?

Blindness has many causes. Worldwide, the leading causes of blindness are cataracts, trachoma, leprosy, and vitamin A deficiency. The other causes are diabetes, glaucoma, macular degeneration, and accidents (such as chemical burns or injuries from cords, fishing hooks, fireworks, racket balls, and similar objects).

Other causes include:

• blocked blood vessels
• complications of premature birth (retinopathy of prematurity)
• complications of eye surgery
• lazy eye
• optic neuritis
• stroke
• Tay-Sachs disease
• retinitis pigmentosa
• retinoblastoma
• lead poisoning
• optic glioma

How is the diagnosis made?

A complete and thorough eye examination is performed. The treatment plan depends on the cause. The medical history is obtained and a physical examination performed.

Medical history questions documenting blindness in detail may include:

• Time pattern
  -When did this begin?
  -Did it occur suddenly or gradually?
  -Does it occur only occasionally? How often?
  -How long does it last?
  -When does it occur, in the evening, morning, or all the time?
  
• Quality
  -Is the blindness complete?
  -Is there any residual vision - for example, can light and dark be distinguished?
  -Are both eyes affected?
  
• Other symptoms
  -What other symptoms are also present?
  -Is there eye pain?
  -Is there a headache?
  
• Additional information
  -What medications are being taken?
  -Is there a family history of eye problems or blindness?
  -Have one had an injury to the eye or head?

What is the treatment?

A routine eye examination is performed. The ophthalmologist checks visual acuity, eye movements, pupils, inside of the eye (ophthalmoscopy), and eye pressure (tonometry) when indicated. An overall medical evaluation is done if indicated. Loss of vision should never be ignored, thinking it will get better, one should 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 have a short amount of time where they can be successfully treated.