What are refractive disorders

The eye normally creates a clear image because the cornea and lens bend (refract) incoming light rays to focus them on the retina. The shape of the cornea is fixed, but the lens changes shape to focus on objects at various distances from the eye. By becoming thicker, the lens allows near objects to be focused; by becoming flatter, the lens allows objects farther away to be focused. A refractive error occurs when the cornea and lens cannot focus the image of an object sharply on the retina.

What are the symptoms

A person who has a refractive error may notice that vision is blurred. For example, a child who becomes nearsighted may have difficulty with schoolwork.

What causes refractive disorders

The lens and cornea may not bend light correctly for several reasons. The eyeball may be too large for the optical power of the focusing system. Because of this, light is focused in front of (rather than directly on) the retina, and the person has trouble clearly seeing distant objects. This is called nearsightedness or myopia. In some people, the eyeball is too small for the optical power of the focusing system, so light is focused behind the retina. This is called farsightedness or hyperopia. People who are farsighted have trouble clearly seeing anything close. Some people have an imperfectly shaped cornea, which may cause objects to appear blurred from any distance. This condition is called astigmatism .

As people reach their early 40s, the lens becomes increasingly stiff; it does not change shape easily, so it cannot focus on nearby objects, a condition called presbyopia. If a person has had a lens removed to treat cataracts but has not had a lens implant, objects look blurred from any distance. The absence of a lens (as a result of birth defect, eye injury, or eye surgery for cataract) is called aphakia.

How are refractive disorders diagnosed

>A Snellen eye chart is used to determine visual acuity. Visual acuity (sharpness of vision) is measured in relation to what a person with normal vision sees. For example, a person with 20/60 vision sees at 20 feet what a person with normal vision sees at 60 feet. Although refractive errors usually occur in otherwise healthy eyes, testing generally also includes assessments unrelated to refractive error, such as a test of the visual fields and eye movements. The eyes are tested together and individually.

How can refractive disorders be treated

To read more on how refractive disorders can be treated and how Eyerobics can help please select the appropriate disorder: