Strabismus is a visual disorder in which the eyes are misaligned and point in different directions. This misalignment may be constant or intermittent.
When the eyes are misaligned, typically one eye will fixate on objects of interest while the other eye turns in (esotropia), out (exotropia), down (hypotropia), or up (hypertropia).
Often times the eye that is fixing on objects switches; that is, the misaligned eye will fixate and the previously fixing eye will become the misaligned eye. This alternation of the deviating eye is often a good sign suggesting that the vision in each eye is equal.
On the other hand, if the eyes do not switch fixation (one eye is constantly the fixating eye and the other eye is constantly the misaligned eye), then the fixating eye is favored and almost always has better vision.
Esotropia and exotropia are common conditions among children. Eye misalignment typically results in double vision in adults, but the developing brain in a child deals with double vision by suppressing one of the images. Therefore, abnormal eye alignment in childhood blocks normal binocular vision development (as the brain learns to rely on only one image from the fixing eye).
Although the avoidance of double vision is beneficial in some regard, this adaptation by the developing brain is also detrimental because the ignored eye loses the ability to see perfect “20/20” vision – a condition called amblyopia.
Amblyopia is decreased vision in a perfectly healthy and well-formed eye which occurs because of a loss of the connection between an eye and the brain during a critical period of vision development from birth to 8 or 9 years of age. Young patients with eye misalignment also typically have poor stereo or 3D vision and depth perception.
Strabismus in adults often results in double vision because the brain has been trained to receive images from both eyes. Adults with strabismus are not at risk of developing amblyopia because the connections between the eye and the brain are already formed and cannot be suppressed.
In infants, it is often difficult to determine the difference between true strabismus (misaligned eyes) and eyes that appear to be crossed. Young children often have a wide, flat nasal bridge and a fold of skin at the inner eyelid (epicanthal fold) that tends to hide the white sclera of the eye when looking in side gaze, thus causing the eyes to appear crossed.
An ophthalmologist like Dr. Baribeau can readily distinguish true strabismus from the optical illusion called pseudo-strabismus which resolves spontaneously with growth during childhood development. Children should undergo vision screening by a family doctor, pediatrician, or ophthalmologist at birth, six months of age, three years of age, and preschool to detect potential eye problems early while they can still be treated.