Amblyopia and astigmatism are two different eye conditions that can occur separately or concurrently, with astigmatism leading to amblyopia. Astigmatism describes a condition in which the cornea, the clear dome-shaped covering over the front of the eye, curves unevenly. Astigmatism can lead to vision disturbances. A severe disturbance in vision can lead to amblyopia, or "lazy eye," in which one eye drifts inward or outward and may "stop seeing," MayoClinic.com reports. Amblyopia occurs because the brain "turns off" the eye, not because the eye lacks the structural ability to see.
Relationship
Astigmatism leads to amblyopia in some cases, Erin Harvey reports in the June 2009 issue of "Optometry and Vision Science." However, astigmatism can occur without amblyopia, and amblyopia can occur for other reasons besides astigmatism. Amblyopia affects around 2 to 3 percent of children, the National Eye Institute says.
Causes
Astigmatism is most often inherited, but may also occur from injury to the cornea or from eye surgery, All About Vision says. Amblyopia is the brain's attempt to see more clearly by using only the better eye to see. When vision blurs or becomes distorted if both eyes are used, the brain turns off the vision to the worse eye. Over time, the eye may lose the ability to see and become structurally and functionally blind.
Symptoms
Astigmatism often causes blurred vision because of the irregular shape of the cornea. Light entering the cornea normally focuses equally on all planes of the retina when the cornea curves equally in all directions. The irregular shape distorts vision, like looking in a fun house mirror. Headaches or eye strain may occur in people with astigmatism, which can occur in either nearsighted or farsighted people, All About Vision says. Amblyopia may cause the eyes to appear crossed or unfocused.
Treatment
Treatment for astigmatism can consist of eyeglasses, hard or soft contact lenses, or corneal re-shaping with LASIK or other refractive surgery. Amblyopia is often treated by patching the normal eye for several weeks or months, the National Eye Institute explains, so that the brain is forced to use the dysfunctional eye.
Complications
If amblyopia occurs due to astigmatism, irreversible functional blindness may occur if the amblyopia isn't corrected. Amblyopia is the main cause of vision impairment in one eye in young and middle-age adults, according to the National Eye Institute.
