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.

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

Loss of vision

Blindness has many causes. In the United States, the leading causes are diabetes, glaucoma, macular degeneration, and accidents (such as chemical burns or sports injuries).

Worldwide, the leading causes of blindness are cataracts, onchocerciasis (river blindness), trachoma, leprosy, and vitamin A deficiency.

Other causes include:

• Blocked blood vessels
• Complications of premature birth (retrolental fibroplasia)
• Complications of eye surgery
• Lazy eye
• Optic neuritis
• Stroke
• Tay-Sachs disease
• Retinitis pigmentosa
• Retinoblastoma
• Lead poisoning
• Optic glioma