Science Fair Project Encyclopedia
Strabismus (sometimes called crossed or wandering eye) is a disorder of the eyes involving a lack of coordination between the muscles of the eyes. Essentially, the eyes do not point in the same direction. This prevents bringing the gaze of each to the same point in space, preventing proper binocular vision, which may adversely affect depth perception.
When strabismus is congenital or develops in infancy, it can cause amblyopia, in which the brain ignores input from the deviated eye although it is capable of normal sight. Since strabismus can cause amblyopia, which is sometimes referred to as lazy eye, it is sometimes itself inaccurately referred to as lazy eye.
In addition to the visual problem, strabismus can be considered a cosmetic problem owing to the appearance of the deviated eye. One study reported that 85% of adult strabismus patients "reported that they had problems with work, school and sports because of their strabismus". The same study also reported that 70% said strabismus "had a negative effect on their self-image" .
Strabismus may be concomitant or incomitant. Concomitant strabismus means that the strabismus is equal regardless of which direction the gaze is targeted. This indicates that the individual extraocular muscles function individually, but that they may simply not be aimed at the same target. Concomitant strabismus in a child under the age of 6 rarely indicates serious neurologic disorder . Blindness in one eye usually causes concomitant strabismus, with the eye of a child turning inward, and that of an adult turning outward.
Incomitant strabismus occurs when the degree of misalignment varies with the direction of gaze. This indicates that one or more of the extraocular muscles may not be functioning normally. Types of strabismus include:
- esotropia, or one eye turning inward;
- exotropia , or one eye turning outward;
- hypertropia , or one eye turning upward.
- hypotropia , or one eye turning downward.
Strabismus testing consists of general inspection, corneal light reflex testing, and cover testing. During cover testing, each eye is covered to detect whether or not it is the strabismic eye. If the eye being tested is the strabismic eye, then it will fixate on the object after the "good" eye is covered. If it is the "good" eye, there will be no change in fixation, as it is already fixated. Depending on the direction that the strabismic eye deviates, the type of tropia or phoria may be assessed.
Strabismus can be treated with surgery, eyeglasses or prisms, depending on the underlying reason for the misalignment. Surgery is used to effectively shorten, lengthen or change the position of one or more of the eye muscles, allowing the eyes to align properly. Glasses affect the position by changing the person's reaction to focusing. Prisms change the way light, and therefore images, strike the eye, simulating a change in the eye position.
Early treatment of strabismus in infancy can reduce the chance of developing amblyopia and depth perception problems. Eyes that remain misaligned can still develop visual problems. Prism lenses can also be used to provide some comfort for sufferers and to prevent double vision from occurring. However, it does not cure the condition.
The contents of this article is licensed from www.wikipedia.org under the GNU Free Documentation License. Click here to see the transparent copy and copyright details