Disorders of vision are very common; most people have a visual problem at some time in their lives. The most common disorders of vision are shortsightedness (myopia), longsightedness, (hypermetropia), and astigmatism, which are types of refractive (focusing) errors. Most refractive errors can be corrected by aids, such as glasses or contact lenses, or cured by surgical techniques.
The opening articles in this section discuss refractive errors and show how variations in the size and shape of the eye may lead to distortions of vision. Tests and treatments for refractive errors are also described. However, special tests for children’s vision are covered separately (see Vision tests in children). Presbyopia, the deterioration of vision that occurs with aging, is covered next.
The following articles describe colour blindness, a condition that is more common in men, and serious visual problems, including double vision and partial or total blindness.
Disorders that affect the structure of the eye, including glaucoma, are covered elsewhere (see Eye disorders), as are blindness at birth (see Congenital blindness) and two disorders that mainly affect children: crossed eyes (see Strabismus) and abnormal vision in an eye that is otherwise structurally normal (see Amblyopia).
For further information on the structure and function of the eye, see Eyes and Vision.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.