What is strabismus?
Strabismus is an imbalance of eye movement which means that both eyes don’t look in the same direction. Due to a loss in coordination of the ocular axis, binocular vision is affected meaning that instead of seeing with both eyes, the child is only able to see with one.
Strabismus can be classified as horizontal (one eye deviates outwards or inwards) or vertical (one eye is higher or lower than the other) according to the direction of misalignment.
What is the cause of strabismus?
The majority of cases in infancy are caused by changes in the eye muscles or the coordination of these muscles.
Another common cause in children is a lack of visual sharpness in one of the eyes. When one eye cannot see, or sight is worse compared to the other eye, a lazy eye develops. Lazy eyes tend not to focus properly and suffer from strabismus. The most frequent cause of a lazy eye is a difference in prescription between the eyes meaning that the eye with the stronger prescription sees worse and becomes lazy. As well as problems with the eye’s prescription, there are also other rarer but more serious causes of lazy eye such as congenital cataracts, cornea damage, drooping upper eyelids, intraocular tumours, and retinal diseases. Therefore, any child suffering from strabismus must see an ophthalmologist for a thorough eye examination.
Cases of strabismus in family history, particularly in the immediate family, increase the likelihood of a child suffering from the condition.
What problems can strabismus cause?
Strabismus can cause several problems:
Amblyopia or lazy eye. As mentioned, amblyopia or lazy eye can be the cause of strabismus since when one eye cannot see, or sight is inferior, it tends to become misaligned. Conversely, the lazy eye could also be the consequence of strabismus given that when one eye is misaligned, sight is inferior and the eye becomes lazy. Amblyopia is the main complication for strabismus since if it’s not treated in time, the condition becomes irreversible.
Loss of binocular vision. Both eyes must be aligned and have good vision for binocular vision to occur. Under normal circumstances we see through both eyes at the same time and this binocular vision is essential for depth perception (seeing in three dimensions).
Wry neck or torticollis. Patients tend to turn their head to see from a position where the eyes are least misaligned. If this unnatural head position is maintained for a long time, the patient can develop permanent contracture of the neck.
Undesired appearance of the patient.
How can strabismus be corrected?
Strabismus can be treated in several ways:
- The first and simplest option is to use glasses. This treatment is particularly useful for convergence insufficiency (when the eye deviates inwards) and its associated farsightedness.
- Patients for whom glasses are unsuitable or insufficient, can undergo surgery that strengthens or weakens some of the eye muscles in order to correct the existing misalignment.