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.
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.
- What is blindness?
- What are the different types of blindness?
- What causes blindness?
- What are symptoms and signs of blindness?
- How is blindness diagnosed?
- What are treatments for blindness?
- What is the prognosis for blindness?
- When is someone considered legally blind?
- Is blindness preventable?
- Find a local Eye Doctor in your town
What is blindness?
Blindness is defined as the state of being sightless. A blind individual is unable to see. In a strict sense the word blindness denotes the condition of total blackness of vision with the inability of a person to distinguish darkness from bright light in either eye. The terms blind and blindness have been modified in our society to include a wide range of visual impairment. Blindness is frequently used today to describe severe visual decline in one or both eyes with maintenance of some residual vision.
Vision impairment, or low vision, means that even with eyeglasses, contact lenses, medicine or surgery, you don't 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. Approximately 80% of blindness occurs in people over 50 years old
What are the different types of blindness?
Color blindness is the inability to perceive differences between some of the colors that others can distinguish. It is most often inherited (genetic) and affects about 8 % of males and under 1% of women. People who are color blind usually have normal vision otherwise and can function well visually. This is actually not true blindness.
Night blindness is a difficulty in seeing under situations of decreased illumination. It can be genetic or acquired. The majority of people who have night vision difficulties function well under normal lighting conditions. This is not a state of sightlessness.
Snow blindness is loss of vision after exposure of the eyes to large amounts of ultraviolet light. Snow blindness is usually temporary and is due to swelling of cells of the corneal surface. Even in the most severe of cases of snow blindness, the individual is still able to see shapes and movement.
People often say, "I am 'blind as a bat' without my glasses." All bat species have eyes, and most have excellent vision. More importantly, the term blindness means the inability to see despite wearing glasses. Anyone who has access to glasses and sees well with the glasses cannot be termed blind.
Next: What causes blindness?
Viewers share their comments
Get breaking medical news.