EXOTROPIA


Exotropia is a condition in which one or both eyes turn outwards. This deviation can occur intermittentlyor can be a permanent fixture. It can affect every age group, but we will only focus on paediatric causes and treatment within this article.



THE MAIN PROBLEMS THAT CHILDREN WITH EXOTROPIA WILL BATTLE WITH:
If a child’s eyes do not look in the same direction at the same time, the information sent to the brain does not describe the “whole” picture. In fact, each eye is sending a different image.

This results in a child’s brain being unable to form three-dimensional images and to perceive how close or far away an object is.

The ability to visualize objects in three-dimension is termed stereopsis.

It helps with performance of skills such as:
  • Catching
  • Grasping
  • Throwing
  • To walk over and around obstacles at greater speed and with more assurance
  • It helps to keep a child safe and to interact with the world more efficiently

Without these visual modalities, a child can be limited by what career they can follow when they become an adult.

You will agree that it is therefore vital to catch this condition early so that the child concerned has the best possible chance of developing these important visual skills.

THE DIFFERENT TYPES OF EXOTROPIA AND HOW TO NOTICE THEM:
As mentioned previously, the eye can either deviate outwards periodically or constantly. Apart from these two types, there is another type of exotropia known as convergence insufficiency.
CONSTANT DEVIATION
The constant form can present as early as 2 to 6 months of age and is called “early-onset” or “Infantile” exotropia. It is rarely seen at birth (congenital exotropia).

This formcan be associated with neurological disorders, skull or facial irregularities or disease of the eye itself. This child will require a peadiatric as well as an ophthalmological review.

INTERMITTENT DEVIATION
The variable or intermittent type of exotropia tends to make itself known between the ages of 2 and 5 years of age and is the most common type of exotropia. Here, the eye or eyes turn outward when they are “put under strain”. This can happen when looking at a distant object or at a near one.
CONVERGENCE INSUFFICIENCY
In this condition, the eyes do not work well as a team. This is clearly evident when the eyes need to look at an object nearby, like the writing on a page. Instead of the eyes working together, one turns outward. Usually, Orthoptists are of great help in such cases. They assess the child and then teach him/her, through specific eye exercises, to realign their eyes. This therapy enables the eyes to work as a team.
SOMETIMES, THE APPEARANCE OF EXOTROPIA MAY BE DECEIVING
In some cases of exotropia, there is an underlying issue that makes the eyes appear to turn outwards, when in fact they are perfectly aligned. An example of this, is a large distance between the two eyes. This gives the illusion that the child has an exotropia, when, their eyes actually are straight.
HOW TO NOTICE EXOTROPIA IN A CHILD
The following signs or symptoms occur early in the condition:
  • One eye or both eyesturn outwards, especially when the child is looking at an object in the distance or if the child is tired, daydreaming or has a fever
  • If you make the child aware that their eyes are turning outwards, they can usually correct this deviation, usually by blinking
  • As soon as a child looks at an object that is close to them, after looking at an object in the distance, the turned outward eye/s straighten up
  • You may notice the child closing one eye to help them see clearly
  • A child may complain of “tired eyes” and of headaches, and may even complain of seeing double
If no medical advice is sought and the exotropia progresses, the outward deviation of the eye can become more fixed or “constant”.

At this point, the child who complained about seeing double, may stop doing so. The brain has become so confused at receiving messages from two eyes that see different images, that it can “turn off” one of the eyes (amblyopia).




You may ask the question whether it is absolutely necessary to see an eye specialist if you suspect that your child may suffer from exotropia. The simple answer is, yes, it is vital for an infant or child to be examined by an experienced ophthalmologist.

Firstly, the doctor (ophthalmologist) will need to exclude any serious underlying problems that require assessment by other specialties, such as genetic or craniofacial disorders that may be life-threatening.

Secondly, with the correct diagnosis and treatment, the ophthalmologist can tailor a treatment plan specific for the child.

When booking an appointment to see an ophthalmologist, ensure that it is a time of day that your child usually concentrates well and that he or she has recently eaten.
THE OPHTHALMOLOGIST WILL EXAMINE THE FOLLOWING:
  • How the eyes move
  • Whether the child needs glasses or not
  • The inner structures of the eye to ensure that there is no pathology there that could cause the eye (s) to turn outwards
ONCE A DIAGNOSIS IS MADE, THE DOCTOR WILL DECIDE WHAT THE BEST COURSE OF TREATMENT IS, WHICH MAY REQUIRE:
  • Wearing the correct glasses or
  • Seeing an orthoptist to teach the child how to train their eyes to work together or
  • To have surgery
In the case of surgery, it is done under general anaesthesia. The eye can move using 6 different muscles that operate between the eyeball and the bony eye socket. By shifting the various muscles, the eye is realigned to its correct position.After a careful assessment, the ophthalmologist will know which of these muscles need to be moved and they will be able to calculate down to the millimeter how far the muscle should be moved! These surgeries are often highly successful.

Did you know the following facts?
  1. Did you know that the normal pressure in the eye is 12 - 20 mmHg? This means that even a small change to the pressure can have an effect. To give you a comparison, the pressure in a new tennis ball is roughly 1520 mmHg.
  2. Near-sightedness can cause exotropia.
  3. Orthoptistsare vital members of the ophthalmology team. They are experts in eye misalignment assessment and management.
References:
  • “Clinical Ophthalmology” Seventh Edition by Jack Kanski. Pages 770 – 772
  • “Oxford Handbook of Ophthalmology” Second Edition by A. K. O. Denniston and P. I. Murray. Page 657 and pages 660 - 661
  • “Ophthalmology Review Manual” by Kenneth Churn and Michael Zegans. Pages 505-506
  • “Ophthalmology Secrets in Colour” Third Edition, by J. F. Vander abd J. A, Gault. Pages 243-244
  • Royal Free London NHS Foundation Trust


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