Strabismus is any misalignment of the eyes in which the eyes are not pointing in the same direction. The eyes are disassociated, thereby not working together to maintain binocular vision. In the normal state, the brain and eye muscles work together to remain aligned. A normal newborn infant may have eyes which cross or drift outwards, as the young brain and eyes are trying to figure things out. This process can be normal until age 3-4 months in fullterm newborns, and up to 4-6 months in premature infants born at 34 weeks gestational age and younger. But after this period, the eyes should look straight on a consistent basis.
If the eyes of an infant or young child remain misaligned for long, the critical time frame for developing binocular vision may be lost. Also, one or both eyes may become permanently weak in their visual acuity (amblyopia), further complicating the problem.
Types of strabismus:
Pseudostrabismus: occurs when the eyes are actually aligned normally, but the shape of the eyelid skin or nasal bridge creates an optical illusion of crossed or misaligned eyes. This still warrants a medical eye exam since many times it is difficult to differentiate pseudostrabismus from true strabismus.
Esotropia: occurs when one eye crosses in towards the nose in relation to the other. There are numerous subtypes of esotropia including congenital esotropia, accommodative esotropia, mixed mechanism esotropia, paralytic esotropia, and Duane’s type esotropia.
Exotropia: occurs when one eye drifts outward, towards the temple, in relation to the other eye. The subtypes of exotropia include congenital exotropia, intermittent exotropia, paralytic exotropia, and Duane’s type exotropia.
Hypertropia/hypotropia: occurs when one eye deviates up or down in relation to the other eye.
Strabismus can occur because of high or unequal refractive errors, amblyopia, hereditary factors, prematurity, spontaneous causes, illness, trauma, brain abnormalities including tumors, or thyroid issues. When strabismus is suspected, a comprehensive medical eye exam with a pediatric eye specialist is very important.
Treatment for strabismus may include the use of glasses full-time, bifocals, patching the straight eye for hours a day, instilling a dilating drop in the straight eye a few times per week, surgery of the eye muscles, Botox injection of the eye muscles, or a combination of the above. A child with strabismus is followed closely every 2-6 months until about the age of 9, depending on the severity of the condition.