However, he or she may close one eye to compensate for the problem. In children, the reason for not seeing double is that the brain may ignore the image it receives from the squinting eye. This shutting down is known as Suppression. Generally, exotropia progresses in frequency and duration. As the disorder progresses, the eyes start to turn out when looking at close objects as well as those in the distance. If left untreated, the eye may turn out continually, causing a loss of binocular vision or stereopsis. In young children with any form of strabismus, the brain may learn to ignore the misaligned eyes image and see only the image from the best-seeing eye. This is called amblyopia, or lazy eye, and results in a loss of binocular vision, impairing depth perception. In adults who develop strabismus, double vision sometimes occurs because the brain has already been trained to receive images from both eyes and cannot ignore the image from the turned eye. Additionally in adults who have had exotropia since childhood, the brain may adapt to using a "blind-spot", whereby it receives images from both eyes, but no full image from the deviating eye, thus avoiding double vision, and in fact, increasing peripheral vision on the side of the deviating eye. According to a study published in the American Journal of Ophthalmology, over 90 percent of children with intermittent exotropia become nearsighted by the time they’re 20. Causes
The causes of exotropia are not fully understood.
There was insufficient evidence related to the benefits conferred by surgical interventions.The surgical procedure for the correction of exotropia involves making a small incision in the tissue covering the eye to reach the eye muscles. The appropriate muscles are then repositioned to allow the eye to move properly. The procedure is usually done under general anaesthesia. Recovery time is rapid, and most people are able to resume normal activities within a few days. Following surgery, corrective eyeglasses may be needed, and in many cases, further surgery is required later to keep the eyes straight. When a child requires surgery, the procedure is usually performed before the child attains school age. This is easier for the child and gives the eyes a better chance to work together. As with all surgery, some risks occur. However, strabismus surgery is usually a safe and effective treatment. References
External links

eMedicine on congenital exotropia