What is an Accommodative Esotropia?
Accommodative esotropia in children is one type of esotropia. This is one of the few squints which are corrected by the child wearing glasses or high plus powered lenses (hyperopic correction) and not by strabismus surgery. Esotropia is a type of squint (disturbed ocular alignment) where the eye turns inwards or towards the nose.
Following are the forms of esotropia
- Infantile esotropia - Age of onset of this squint is at birth or within the first 6 months. Here the squint is a large angle squint and is a constant esotropia. The amount of squint does not usually change. This is treated by strabismus surgery. This is also known as non-accommodative esotropia.
- Accomodative esotropia - Onset of esotropia is usually at 3-5 years of age and here the amount of squint is changing. It may be an intermittent esotropia and there may be times when the parents may not see the squint at all. This is treated with glasses or refractive correction.
- Partially accomodative esotropia - Here refractive correction or glasses will correct part of the squint and strabismus surgery will correct the residual esotropia.
When does Accommodative Esotropia occur in Children?
Accommodative esotropia occurs after the first few years of life usually at 3-5 years of age though sometimes we do see this squint in younger children. Parents often complain of the child’s eyes squinting inwards but only sometimes, not all the time. They may also add that the squinting is more when the child is looking at near objects.
Why does Accommodative Esotropia occur?
Children with accommodative esotropia are born with a high hyperopic error, which is a type of refractive error, or a high plus power. When someone has a high plus power they have to accommodate to see clearly. Let's say accommodate means to focus. So if someone with a high plus power focusses then they can see clearly inspite of not wearing glasses.
However, there is a direct link between accommodation and convergence or how much both the eyes move inwards. Thus every time we focus the eyes turn a little inwards. The more we focus the more they turn inward. This is known as accommodative convergence.
Since these children have a high plus power (refractive error) they have to accommodate a lot and thus their eyes turn inwards. One will notice the squint only when the child accommodates or focuses or attempts to see things clearly. If the child is daydreaming and not focussing on things then one may not notice the squint at all. Thus accomodative esotropia is also known as refractive esotropia.
The child may present with the following
- Esotropia - eyes squinting inwards
- The squinting occurs in one eye at one time. It could always be in one eye, the right or the left or parents may notice sometimes the right and sometimes the left.
- Intermmittent esotropia or a constant esotropia
- Double vision or diplopia - Not all patients with strabismus may have diplopia
- Moderate to poor stereopsis or quality of binocular vision
- Normal or decreased visual acuity or vision
- Amblyopia or a lazy eye
Examination of a child who comes with an esotropia
Here are the steps of examination
- Detailed history is taken
- Vision checking
- Eye power check up
- Detailed squint examination for both far and near - A squint is measured with prisms and is written as prism diopters and angle of deviation is measured. This is done while showing the child an accommodative target, which means the child should be using least amount of focussing for seeing far objects and maximum focussing for seeing near objects.
- After this the child is dilated with two drops. Tropicamide eye drops and Cyclopentolate eye drops. Sometimes, instead of these drops another eye drops by the name of atropine eye drops are used to dilate the pupils.
- An eye power check up is done again. When we examine children we need to put these drops to get accurate readings of eye power.
- Usually we find a high plus power or hyperopia.
- Child is prescribed glasses.
- Child is seen every 2 months till child achieves ocular alignment
What is the treatment of Accommodative Esotropia?
Accommodative esotropia occurs because of the child focussing to see clearly. Thus while the goal of treatment is to achieve ocular alignment, we have to focus on treating the eye power
Thus the initial treatment can be one of the two
- Glasses with a hyperopic correction or a plus power.
- Contact lenses - not usually preferred because the children are young
Lasik eye surgery can correct hyperopia upto a certain level. If when the child is 19 years old and chooses to get a lasik then the eye power will be treated and so will the squint.
Problems faced by children with the glasses
The child is used to focussing to see clearly. We, as your eye doctors, have given him a hyperopic correction so that now the child does not have to focus. However, the child does not know that. The child's eyes as a reflex continue to focus. This can cause the child to have blurry vision with the glasses in the intiial few weeks. Its important that the parents encourage their child to wear glasses even when the vision is blurred.
Gradually as the child's eyes stop focussing or accomodating, the vision becomes clear and also the squint reduces. As the child starts noticing this improvement in vision, she becomes less reluctant to wear glasses.
Possible outcomes after giving glasses
There are two possible outcomes once the child with accommodative convergent esotropia starts wearing glasses
- Gradually the squint reduces and the childs vision improves in one or both eyes. Over the next few months or a year the child does not have a squint with the glasses on and has 6/6 vision or 100% vision.
- The squint reduces but does not go away completely. THere is a residual deviation. When this happens we wait for a 2-3 visits, each being 2 months apart before calling it a partially accomodative esotropia. As mentioned earlier partially accomodative esotropia will need glasses with a hyperopic correction as well as strabismus surgery to correct the squint.
- The childs squint reduces when the child looks at a far away object but the convergent deviation is visible when the child looks at anything near. This is known as an accomodative squint with a high AC/A ratio. AC stands for accomodative convergence and A stands for accomodation. Usually, the rule is that for every diopter of focussing that one does to see clearly the eyes move inwards or converge by 3-4 prism diopters. In this situation the child converges by greater than 3-4 prism diopters and thus has a squint for near.
- When we see a child who is wearing the correct hyperopic correction and does not have a squint for far but for near, we have to prescribe bifocal glasses to the child. Bifocals are glasses that have two powers in them, one for near and one for far. Over the years the bifocal segment is usually weaned off.
- The child's vision may not improve to the last line. Most likely the squint led to development of Amblyopia or a lazy eye. Treatment for Amblyopia is done with patching the better eye. Recently, eye exercises have shown to have a very beneficial role in treating amblyopia. Amblyopia is however, more common in infantile esotropia because this is a contstant squint.
At Eye Solutions we have two amblyopia treatments that are effective even in adults.
Will the glasses or squint ever go away
The eye power may reduce as the child grows older however very rarely would the glasses go away completely. So is the case with the squint. Parents always mention that the squint is not seen with the glasses on but it comes back when the glasses are taken off.
We expect that to happen and are not really surprised because as soon as the glasses are taken off the child has to focus again and the eyes turn inwards.
Can accommodative esotropia be treated with surgery ?
As mentioned earlier Infantile esotropia or congenital esotropia is always treated with surgery. On the other hand accommodative esotropia is treated with glasses.
Partially accommodative convergent esotropia may be treated by surgery. Even children with high AC/A ration can be operated upon to treat or correct the need to wear bifocal glasses.