Esotropia is a strabismus condition where the eye turns inward (toward the nose). This condition may be evident intermittently (not all the time) or constantly. The deviation, or eye turn, may occur while fixating (looking at) distance objects, near objects, or both. Esotropia is also often called cross-eyed.
Much more common than infantile exotropia, infantile esotropia is evident shortly after birth and often before 6 months of age. Infants don't have great eye movement control in the first few weeks of life, but by 6 months the child should have full control of eye movements. Infantile tropia (exo- or esotropia) can be very debilitating to the development of normal binocular vision, as the child starts life unable to develop normal visual skills, such as stereopsis (depth perception). Infantile esotropia is categorized as beginning at birth or during the first year of life.
Intermittent esotropia is a subset of esotropia that is present only once and a while. The patient often can control eye positioning most of the day, but an eye may turn inward with a stressful condition or extended near work.
This is technically a subset of intermittent esotropia. Unlike patients that are near-sighted (myopia), patients with a high far-sighted (hyperopia) correction can focus the eye naturally to make images clearer. Naturally focusing an image (called accommodation) is often paired with a slight inward turn of the eyes. High hyperopia patients over-focus to the point that an eye starts to turn inwards abnormally. This is usually corrected with glasses and sometimes bifocals (yes even on kids!). Accommodative esotropia is one of the most common forms of esotropia
Alternating esotropia refers to how a patient fixates. A patient with a constant esotropia fixates with one eye, all the time. This would be called a unilateral (right or left) esotropia. Patients with an alternating fixation pattern switch fixation between each eye.
Mechanical esotropia is often due to fibrosis (or scar tissue) that prevents the eye from moving inward. Some conditions, such as overactive thyroid, can leave deposits in muscles and cause an abnormal tightness for an eye muscle to move. Damage from broken bones around the eye (the area called the orbit) may also limit eye movement.
This often occurs in patients younger than 5 years of age that have severely lost vision in one eye. The brain is unable to fuse the images from the normal eye and the eye that has lost vision, so the eye drifts inwards.
Microtropias are small deviations of the eye that can be quite tricky to see. Inward microtropia (microesotropia) is much more common than microexotropia.
The distinguishing sign of esotropia is one or either eye wandering inward. Symptoms may be mild or severe. If suppression of the deviating eye occurs, the patient can have diminished binocular vision and diminished stereopsis. Patients may also experience diplopia (double-vision). Asthenopia (eye fatigue) can also occur with reading.
Causes of esotropia are mostly unknown. Children with a family history of the disorder are more likely to get them. They are also common in children who have other systemic (chromosomal or neurologic) disorders.
New-onset esotropia is called an acquired esotropia. If the condition occurs rapidly, it's termed acute, acquired esotropia. Most often acute esotropia cases are more concerning because the underlying cause is often damage to the 6th cranial nerve. There is only one cranial nerve the controls the lateral rectus muscle on the ear-side of each eye. This nerve (called the abducens nerve) has a long patch from its origin to the muscle, and can be easily damaged. Head trauma, increased intracranial pressure, diabetes and other vascular disorders, migraines and multiple other conditions could cause a new esotropia.
Management of esotropia is based on a number of factors. The overriding principles are: