Blindness

  • Medical Author:
    Andrew A. Dahl, MD, FACS

    Andrew A. Dahl, MD, is a board-certified ophthalmologist. Dr. Dahl's educational background includes a BA with Honors and Distinction from Wesleyan University, Middletown, CT, and an MD from Cornell University, where he was selected for Alpha Omega Alpha, the national medical honor society. He had an internal medical internship at the New York Hospital/Cornell Medical Center.

  • Medical Editor: William C. Shiel Jr., MD, FACP, FACR
    William C. Shiel Jr., MD, FACP, FACR

    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

Blindness Causes

The causes of loss of vision are extremely varied and range from conditions affecting the eyes to conditions affecting the visual processing centers in the brain.

Quick GuideCommon Eye Problems and Infections

Common Eye Problems and Infections

Blindness facts

  • Blindness is strictly defined as the state of being totally sightless in both eyes. A completely blind individual is unable to see at all. The word blindness, however, is commonly used as a relative term to signify visual impairment, or low vision, meaning that even with eyeglasses, contact lenses, medicine or surgery, a person does not see well. Vision impairment can range from mild to severe.
  • Worldwide, between 300 million and 400 million people are visually impaired due to various causes. Of this group, approximately 50 million people are totally blind, unable to see light in either eye. Eighty percent of blindness occurs in people over 50 years old.
  • Common causes of blindness include diabetes, macular degeneration, traumatic injuries, infections of the cornea or retina, glaucoma, and inability to obtain any glasses.
  • Less common causes of blindness include vitamin A deficiency, retinopathy of prematurity, vascular disease involving the retina or optic nerve including stroke, ocular inflammatory disease, retinitis pigmentosa, primary or secondary malignancies of the eye, congenital abnormalities, hereditary diseases of the eye, and chemical poisoning from toxic agents such as methanol.
  • Temporary blindness differs in causes from permanent blindness.
  • The diagnosis of blindness is made by examination of all parts of the eye by an ophthalmologist.
  • The universal symptom of blindness or visual impairment is difficulty with seeing. People who lose their vision suddenly, rather than over a period of years, are more symptomatic regarding their visual loss.
  • The treatment of blindness depends on the cause of blindness.
  • The prognosis for blindness is dependent on its cause.
  • Legal blindness is defined by lawmakers in nations or states in order to either limit allowable activities, such as driving, of individuals who are "legally blind" or to provide preferential governmental benefits to those people in the form of special educational services, assistance with daily functions or monetary assistance. It is estimated that approximately 700,000 people in the United States meet the legal definition of blindness.
  • In most states in the United States, "legal blindness" is defined as the inability to see at least 20/200 in either eye with best optical correction.
  • Between 80%-90% of the blindness in the world is preventable through a combination of education, access to good medical care, and provision of glasses.
  • Patients who have untreatable blindness require reorganization of their habits and re-education to allow them to do everyday tasks in different ways. In the United States and most other developed nations, financial assistance through various agencies can pay for the training and support necessary to allow a blind person to function.
  • There are countless individuals with blindness, who, despite significant visual handicaps, have had full lives and enriched the lives of those who have had contact with them.
Medically Reviewed by a Doctor on 8/18/2016

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