An eye patch is something a person wears to cover one eye while leaving the other exposed. The patch may be either a piece of cloth attached to a band of elastic to fit around the head or a bandage. In most cases, an eye patch is worn for medical reasons. These patches might be used to cover up eyes that are missing or disfigured or to help correct vision in people with various eye ailments.
Historically, pirates and sailors may have worn eye patches to help their vision quickly adjust to light and dark. Going back and forth from the brightness of the upper ship deck to the pitch darkness below deck frequently resulted in their eyes having to constantly readjust themselves. Wearing an eye patch meant that a pirate already had one eye adjusted to darkness and the other adjusted to the light. This probably saved valuable time, allowing pirates to go quickly from one level to the next without being temporarily blinded until their eyes adjusted.
Eye patches, most often in the form of adhesive patches, are used as vision therapy in the correction of lazy eye, also called amblyopia. This form of treatment is typically used on children because dealing with the problem early often results in complete vision correction. When amblyopia is left untreated beyond childhood, the outcome could be blindness in the affected eye or severe problems with depth perception. The use of an eye patch on the unaffected eye forces the affected eye to focus, which frequently leads to complete vision correction.
Some people wear eye patches to treat diplopia. This condition causes double vision and is diagnosed as either monocular or binocular diplopia. A person with binocular diplopia can see normally when one eye is closed. With monocular diplopia, vision is affected no matter what. People with binocular diplopia benefit more from an eye patch than people with the monocular form of the condition because they can see normally when one eye is covered.
The traditional black eye patch was much more common before the invention of prosthetic eyes. It used to be the only way to cover up a disfiguring eye injury or missing eye. Some people still wear them for medical purposes, and others wear them in an attempt to make a fashion statement. Famous entertainers such as David Bowie and rapper Slick Rick used eye patches for medical reasons, and fans followed suit in an attempt to imitate their idols.