Fully Accommodative Esotropia Flashcards
What is it?
Accommodative esotropia is an inward turning of one or both eyes that occurs with activation of the accommodative reflex. Accommodation is a dynamic process in which the curvature of the eye’s natural lens is temporarily adjusted to improve focus at near or in eyes that are hyperopic (far-sighted). Accommodative convergence described the normal convergence of the eyes in response to accommodation of the lens. The amount of accommodative convergence relative to the degree of accommodation is called the AC/A ratio
There’s two types
) Refractive (normal AC/A ratio) accommodative esotropia caused by uncorrected or under-corrected hyperopia and
2) Non-refractive (high AC/A ratio) accommodative esotropia caused by excessive convergence of the eyes in response to accommodation for near focus, regardless of refractive error. A patient may have a high AC/A ratio in addition to having refractive accommodative esotropia.
When will this happen?
This condition may present anytime from infancy to late childhood, but most often between two and four years of age. Typically, the eyes are straight during infancy and the esotropia will develop as they learn to accommodate for clearer vision. The esotropia is usually initially intermittent, manifesting when the child is tired or focusing at near, but can quickly become constant. Some children may complain of double vision; however, young children will frequently suppress the image from the deviated eye, which can lead to amblyopia. Decompensation of an initially well-controlled deviation can occur in some cases, necessitating a change in refractive correction or surgical intervention.
Aetiology
The aetiology of fully accommodative esotropia is moderate hypermetropia , it is refractive in nature so the cause is purely the patient has moderate hypermetropia. There can be a family history so there can be a hereditary element to fully accomodative esotropia but the child will always have hypermetropia or moderate hypermetropia. When a young child is hypermetropicanf their hypermetropia is uncorrected, they will have retinal blur, and they do one or two things. They can either accommodate through the hypermetropia to see clearly or they can make no effort to accommodate to see clearly. The children that make no effort are generally those that have high amounts of hypermetropia for example +6.00D hypermetropia then its very difficult for that child to accommodate through 6 diopters of hypermetropia to see clearly so they make no effort ans they just stay blurred. This means that they wont develop the esotropia because they are not doing any excessive amounts of accomodation but it does mean they will develop bilateral ametropic amblyopia because the brain is not receiving clear images to develop appropriately.
Aetiology part 2
f the child does accommodate, through the hypermetropia will generally have moderate amounts of hypermetropia like +3.00D , +4.00D and they can push through their hypermetropia to see clearly. They will be doing excessive amounts of accommodation because at a third of a meter they should be doing 3 diopters of accomodation as an example but if they have three 3 diopters of hypermetropia as well, they’ll be doing 6 dioptres potentially at that distance. So with that excess amounts of accomodation comes an excessive amount of accomodative convergence and for some patients this will lead to having an esotropia whilst others may not develop an esotropia and generally will have an esophoria.
Aetiology part 3
The patient who develops esotropia is one is one that generally has insufficient fusional divergence so they have poor binocular function, and this leads to a refractive accomodative esotropia or a fully accomodative esotropia. This individual will have a normal AC/A ratio and if they have a high AC/A ratio and its likely that they’ll be classified differently they wont be exactly a fully accomodative aetiology. If they have a high AC/A ratio they will tend to have convergence excess pattern.
Aetiology part 4
If on the other hand the patient has sufficient fusional divergence so they binocular functions are strong, then they will be able to overcome the fact that they are undertaking excessive amounts of accmodation and thereby accommodate convergence and what they’ll have is an esophoria. The other thing that may help , is if the patient has a low AC/A ratio which means for every diopter of accomodation their not doing as much accomodative convergence as someone with a normal ac/a ratio or high ac/a ratio and this generally will lead to an esophoria or perhaps an orthophoria
Aetiology part 5
Individuals with a fully accomodative esotropia are develop this manifesting this strabismis becsuse of the refractive error that’s present. It’s moderate in size and thereby, they can induce excessive amounts of accommodation to see clearly but that has consequences and for them it has consequences in that they develop an esotropia
Onset
Onset is about 18 months to about 4 years of age, that may vary but that’s generally about when the deviation develops and there is some thinking that it develops more readily around the 2-3 year age range when children are starting to do a little more close work such as colouring in and they’re using their accommodation more than they are used to when they were younger.
Clinical charesticis
In terms of the clinical characteristics, we expect hypermetropia in these patients , when we do a cover test, what you will find is that without glasses, they will have esotropia , and with glasses once you’ve corrected the refractive error so there is no need additional or excessive amounts of accomodation the patient will be straight. We can confirm this as if a cover test with glasses on will show either a esophoria or they will orthophoria. The angle is basic because we have a normal AC/A ratio and there is no impact on the AC/A ratio on this deviation so it tends to be similar near and far.
Cover test
The cover test must be performed with an accomodative target and you need to get the patient to look at the lowest line possible when you’re assessing the patient with an accomodative esotropia. This is extremely important because depending on the level of accomodation that the patient is doing the deviation size will vary.
Management - optical correction
it is important to correct the hypermetropia and this is important as if you leave the patient undercorrected , you run the risk of the strabismis being manifest or remaining manifest with the glasses on. We want to give the patient as much plus you find on retinoscope so that the the patient has the potential of being straight with the glasses on.
Occlusion
is another treatment , as these children often have mild amblyopia. Firstly prescribe glasses as its making the patient bifoveal, this would improve the visual acuity. Also when occlusion is started , once you’ve achieved equal vision ,these children hold their VA and aren’t at risk of losing their vision again or becoming amblyopic again
