Esotropia is a form of strabismus, which is the medical name for a squint and is characterised by the eyes looking in different directions. Esotropia is the main type of strabismus and occurs when one eye looks forward and the other eye looks inwards.
Other types of squint include:
- Exotropia: when the eye looks outwards.
- Hypertropia: when the eye looks upwards.
- Hypotropia: when the eye looks downwards.
In most cases squints affect young children, but they can also affect older people. Squints are very common, affecting around 1 in 20 children born in the UK.
Esotropia is sometimes referred to as being cross-eyed. A squint can affect vision as it affects the ability to produce a coherent 3D image. If the eyes are not pointing in the same direction, two images will be sent to the brain via the optic nerve and this can create a lack of depth perception.
A strabismus can be constant or intermittent, which means the eye can turn all the time (constant) or only sometimes (intermittent). In some cases an intermittent strabismus can be triggered by tiredness, illness or stress.
Types of esotropia
There are different types of esotropia, which include:
This form of esotropia is present at the time of birth. Many children do not have straight eyes when they are born, but in most cases one or both eyes turn outwards over the course of the first two months. Babies can also seem to have cross-eyes because the bridge of the nose is not fully developed. True congenital esotropia is rare and is characterised by the eyes being obviously turned inwards.
Infantile esotropia usually becomes obvious at the age of 2-4 months. Most babies with esotropia look in the opposite direction to gaze at objects or people, which means they use their right eye to look to the left and their left eye to look to the right. In most cases non-surgical treatments can improve the condition. Esotropia can cause poor coordination and different patterns of motor development. Some children skip the crawling stage, for example, and go from sitting and pulling themselves up to standing and walking. Surgery may be required if the strabismus is constant and severe
Accommodative esotropia usually develops after the age of 2 and is caused by poor integration between the accommodative system (used to focus) and the binocular system (used to align the eyes). If esotropia only occurs when a child looks at objects up-close, this can usually be corrected with glasses; however, if esotropia occurs when a child is looking at things in the far distance this usually requires surgery.
What causes esotropia?
Squints are caused when the muscles in the eyes do not work in tandem, meaning the eyes do not move together. Six muscles control the movement of each eye and each muscle pulls the eye in a different direction:
- Lateral rectus muscle: pulls the eye outwards.
- Medial rectus muscle: pulls the eye inwards.
- Superior rectus muscle: pulls the eye upwards.
- Inferior rectus muscle: pulls the eye downwards.
- Superior and inferior oblique muscles: help to stabilise the inward, outward, upward and downward movements.
Esotropia can be congenital, which is when a baby is born with the strabismus. Other possible causes include refractive errors, more commonly known as short-sightedness (myopia), long-sightedness (hypermetropia) and astigmatism. Some underlying health conditions and syndromes can also increase the risk of a child developing esotropia, including Down’s syndrome, Noonan’s syndrome, brain tumours, brain injury and cerebral palsy.
Symptoms of esotropia
Symptoms of esotropia include:
- Blurred vision.
- Double vision.
- One or both eyes pointing inwards (misalignment of the eyes).
- Reduced vision.
- Tilting the head to the side.
- A child rubbing their eyes.
- Problems with the perception of depth.
- Covering or closing one eye to see better.
Complications of esotropia
If left untreated esotropia can contribute to a condition called amblyopia, which is commonly known as lazy eye. Amblyopia can cause serious loss of vision and should be treated as early as possible. It cannot be corrected with glasses, but can usually be improved by prohibiting the child from using their ‘good’ eye by placing a patch over it, which means that the affected eye has to start working. If this method is used in early childhood sight usually improves significantly.
Treatment for esotropia
Treatment depends on the individual and the severity of their condition. In some cases wearing glasses may be sufficient to correct esotropia and improve vision. If a baby is born with esotropia (congenital esotropia) it is likely that surgery will be required.
Surgery for esotropia involves making an incision in the eye and either adjusting the muscles in the inner eye or removing some of the muscle tissue. Surgery is usually carried out under general anaesthetic and recovery time is usually very short.
All newborn babies born with a squint should be monitored closely. If the child has a constant squint, the squint does not improve after two months or it is still present at the age of four months, the child will be referred to a specialist called an orthoptist (a professional trained to assess squints). The child may then be referred to an ophthalmologist (an eye specialist).
All children who receive treatment for esotropia will be advised to see their doctor on a regular basis and have regular eye tests to enable doctors to monitor their progress.