Definition: Eye disorder refers to any number of diseases that affect the eye's structure or function. Eye disorders can be caused by infections, genes, or injury. Examples of eye disorders include conjunctivitis (pinkeye), cataracts, glaucoma, and macular degeneration. Some eye diseases are easily treatable, while others may be cause more serious issues like vision loss. Eye diseases may occur on their own or as part of an underlying condition. An eye care professional can help evaluate the cause and possibly treat the eye disorder.