Esotropia can be divided into various categories each requiring a different treatment plan; each having a different prognosis.
- Congenital Esotropia
- Infantile Esotropia
- Esotropia with Amblyopia
- Accommodative Esotropia
- Partially Accommodative Esotropia
“Congenital” means from birth and, using this strict definition, most infants are born with eyes that are not aligned at birth. Only 23% of infants are born with straight eyes. In the majority of cases, one eye or the other actually turns outward during the neonatal period. Within the first three months the eyes gradually come into more consistent alignment as coordination of the two eyes together as a team develops.
It is common for infants to appear as if they have esotropia, or inward turn of the eyes, because the bridge of the nose is not fully developed. This false or simulated appearance of an inward turning is known as epicanthus. As the infant grows, and the bridge narrows so that more of the white of the eyes (sclera) is visible on the inner side, the eyes will appear more normal.
True congenital esotropia is an inward turn of a large amount, and is present in very few children, but the infant will not grow out of this turn. True infantile esotropia usually appears between the ages of 2 and 4 months.
The baby with infantile esotropia usually cross fixates, which means that he or she uses either eye to look in the opposite direction. The right eye is used to look toward the left side, and the left eye is used to look toward the right side. By definition, they alternate which eye they are looking with. It is more difficult to help this type of strabismus with non-surgical methods, such as Vision Therapy and/or glasses. Sometimes, clear tape applied to the inner third of each lens (occlusion) can reduce the tendency to turn inward. Prisms may aid alignment if the turn is not too large.
Some children who develop strabismus, in which coordination between the two eyes is poor, also have atypical gross motor development patterns. They typically skip the crawling stage with bilateral movements, and go right from creeping to standing. The interplay between gross motor, particularly balance systems (cerebellar and vestibular) and binocular systems (motor control of the two eyes) is also evident in the large number of young children with cerebral palsy who have strabismus.
If the inward turn of the eye is constant, and of a large amount, surgery may be recommended by some health care professionals but many times multiple procedures are needed to obtain perfect alignment of the two eyes for the patient. Furthermore, even multiple surgeries or “revisions” may end up yielding cosmetic benefits only. That is, the two eyes might look normal or “straight” to outside observers, but normal two-eyed vision has not been achieved.
Improvement might only be cosmetic as surgery does not necessarily enable the brain to utilize information from both eyes simultaneously (binocular vision), so eye teaming, eye tracking, stereoptic vision and/or 3D depth perception is often poor following surgical treatment. If surgery is undertaken, the best chance for visual success occurs when the surgeon works with a developmental optometrist who is comfortable in prescribing glasses and Optometric Vision Therapy to encourage perfect alignment of the two eyes with proper fusion and eye teaming. Such a model of cooperative care would be similar to the complementary relationship between an orthopedic surgeon and a physical therapist.
If Amblyopia is present, therapy including binasal medial occlusion, correct eyeglass prescription, prisms, and/or optometric vision therapy is often required so that the turned “lazy” eye develops the capacity to see as well as the preferred eye. This promotes binocular vision (using both eyes together) and provides the greatest outcome.
If excessive inward turning of an eye is first noted around 2 years of age, it may be due to difficulty integrating the focusing (accommodative) system with the eye alignment (binocular) system. Normally when we look across the room or beyond, our eyes are parallel, or straight. However, when we look at things up close, two things happen. We need to converge more (aim both eyes inward at the same time) and we have to input more focus, or accommodate to keep things clear. Children have large amounts of focusing power, and sometimes in getting things clear, inward turning or esotropia results. If the inward turning only occurs up close, as when playing with small objects, making eye contact, coloring, looking at picture books and so forth, the child may just need glasses for near activities to reduce or eliminate the esotropia.
However, if a child is significantly farsighted (hyperopia), an inward turn of the eye may even occur when focusing to look further away, such as television. If the amount of turn is greater at near than far, your optometrist may prescribe a multifocal lens. For children this could be a traditional bifocal with a line, or a form of no-line bifocal or progressive lens. Your optometrist will review with you which is the best option for your child. In addition, Vision Therapy may be of benefit. Accommodative Esotropia should never be treated with surgery.
When the eyes are aligned by corrective lenses sometimes the eyes spontaneously begin to work together. Other times, they need help. Remember, the habit of suppressing or turning off one eye or the other was probably developed over a number of years. The eyes have to be trained to work together again and suppression must be eliminated in order to restore normal eye teaming, depth perception, and stereopsis. The eye doctor might have to patch an eye that was suppressed or turned off and/or employ Vision Therapy.
Intermittent turns usually do not require long term treatment. Vision Therapy may be necessary to improve the muscle coordination and eventually eliminate the bifocal.
Patients with Accommodative Esotropia should never have eye muscle surgery to eliminate the need for glasses. If they do, they will have significant focusing problems when they get older.
In some instances, part of the inward turn is due to basic esotropia, and an additional amount due to the effect of accommodation. Glasses may reduce the amount of eye turn, but it is not totally compensated. Initially, the eye doctor may prescribe prism to compensate for the amount of turn. Office-based Vision Therapy is usually needed. Because vision is a learned process, therapy is often helpful in learning new binocular vision patterns, or restoring normal pathways that have been lost or underutilized. Binocular vision occurs in the visual centers of the brain, not in the eye muscles.