Esotropia – “crosslooking” – is very common today; one eye looks to the nose (or both alternately). It occurs predominantly in the first 2-3 years of life and is usually associated with farsightedness. This sort of strabismus is often accompanied by visual impairment (50%). Esotropia is a sort of strabismus. There are two other sorts: extropia and hypertropia. After our articles about pars plana vitrectomy, epiretinal membrane, macular hole and myodesopsia, we have decideed to write about strabismus. Esotropia (convergent strabismus) is the most common form of childhood strabismus. Howeverm, there are three esotropias:
- Accommodative Esotropia
- Congenital (Infantile) Esotropia
- Intermittent Esotropia
What is Accommodative Esotropia?
Accommodative esotropia is often seen in patients with moderate hyperopia (foresight). A hyperop, in an attempt to achieve accommodating or focuses eye converges, since the convergence is associated with the activation of reflex of the accommodation. Enhanced convergence associated with additional accommodations necessary to compensate hyperopic refractive errors may precipitate if the loss of binocular control occurs and lead to the development of esotropia.
Development of esotropia in these cases depends on the degree of hyperopia presence. In cases where the error rate is small, the child will be able to maintain control because the need for increased compensation to achieve clear images is also small. When it comes to high level hyperopia, it is questionable how clear picture a child can achieve regardless of the applied additional accommodation. Therefore, there is no stimulus that can trigger additional compensation and convergence which thus leads to the development of esotropia. There are also cases when errors are so small that additional compensation allows creating clean image, but it is large enough to affect the binocular control. This case will result in esotropia.
When the sole cause of esotropia is uncorrected hyperopic refractive error, a child should always wear glasses with the appropriate correction, and thus often lead this deviation under control. Such “fully accommodative esotropia” is observed only when the child removes glasses. Many adults which suffer from esotropia from childhood control their strabismus with contact lenses.
There is also another type of accommodative esotropia, known as “excessive converged esotropia.” Children with this condition show an increased accommodative convergence, depending on the required accommodation. In these cases, even when all the presented hyperopic refractive errors are corrected, the child will demonstrate strabismus when viewing small objects or reading small letters. Although these actions require normal accommodative or “focusing” effort, the level of convergence among them is enhanced and leads to esotropia. In these patients, doctors prescribe bifocal lenses as additional hyperopic correction. Lenses reduce the required level of accommodation, and therefore convergence. Many children will eventually learn to control accommodative esotropia, sometimes with the help of orthoptic exercises. However, others will eventually need extraocular muscle surgery to solve the problem.
What is Congenital (Infantile) Esotropia?
Congenital or infantile esotropia is a special sub-section of primary concomitant esotropia. It is a permanent high level esotropia that appears until the 6th month. It is not associated with hyperopia and accommodative effort will not significantly affect the angle of deviation. It is associated, however, with other ocular dysfunction including tinted action of oblique muscle, dissociated vertical deviation, latent nystagmus and defective abduction that occurs as a consequence esotrop tendency to “cross” fixation (perhaps crosslooking). In “cross” fixation people are using the left eye to look to the right, and the right to look to the left. The pathogenesis is unknown, and the early appearance of congenital esotropia is reducing the possibility that an individual will ever develop binocular vision. Opinions about the therapeutic approach divided. Some ophthalmologists advocate surgical solution as the method of choice for the biggest chance for the establishment of binocular vision, while others are not convinced that the potentially good results justify the complexity and high risk of surgery of the patients younger than one year.
What is Intermittent Esotropia?
Intermittent esotropia is a state in which the size of esotropia varies by directing of the view. Intermittent esotropia can occur in childhood or adult age, and occurs due to neurological, mechanical or muscular problem. These problems can directly affect the external eye muscles, but can also affect the innervation and blood supply to the muscles themselves or the surrounding bony structures of the orbit. Examples of conditions in which there is this sort of esotropia include paralysis of 6th vagal nerve, Duane syndrome or orbit injury.
Esotropia Surgery and Therapy
Forecast for each esotrop will depend on the origin and classification of their condition. However, these steps are common in their treatment:
- Identification and treatment of systemic conditions
- Prescribing glasses required to patient and giving them time to get used to them
- Use of occlusion as therapy for any amblyopia present and encourage the alteration
- Where possible, use orthoptic exercises to restore binocular vision
- Where possible, use prismatic correction, temporary or permanent to reducte symptoms of diplopia
- In specific cases in adult patients Botulinum toxin can be used as a permanent therapeutic agent or as a way of preoperatively preventing muscle contractures
- If necessary, do the surgery on the external muscles of the eye for cosmetic reasons, and in rare cases, restoration of binocular vision
Surgical intervention is often an integral part of the treatment, but it cannot possibly solve the problem of strabismus. The eyes are in fact not anatomically parallel. Surgery comes in the cases with larger angle squinting, in particular the so-called phase – “conservative treatment”. Esotropia surgery usually happens from 4th to 6th age at esotropia, (rarely earlier, and only rarely before 2 years). Strabismus is often operated in stages 2 and even 3 times. One should keep in mind all the possible circumstances of development.