What is strabismus?
Strabismus is a condition in which the eyes point in different directions. Other terms used to describe strabismus are “squint”, “wandering eye”, “cross eyed”, or a “lazy eye”. When an eye is turned inwards this is known as a convergent squint or an esotropia.
When an eye is turned outwards this is known as a divergent squint or an exotropia.
When an eye is deviated upwards this is known as a vertical squint or hypertropia.
What causes strabismus in adults?
Approximately 4% of adults have misaligned eyes. Strabismus in adults can develop for many reasons;
- The most common type of adult strabismus involves patients with misaligned eyes from childhood. This problem starts at a time when the patient can suppress (that is, ‘turn off’) one eye and thus avoid double vision. These patients may have undergone surgery to realign their eyes in childhood but the eyes have subsequently drifted inwards or outwards again.
- Weakness of one or more eye muscles caused by damage to the nerves which stimulate the muscles. This usually results in the sudden onset of double vision caused by the eyes becoming misaligned. Circulatory problems are the most common cause of this type of strabismus, such as diabetes and high blood pressure. Inflammation of these nerves, head injuries (often caused by road traffic accidents or falls), or rarely direct pressure on the nerves by a tumour, can also cause this type of strabismus
- Poor vision in one eye for whatever reason may eventually cause that eye to drift outwards or inwards.
- Inflammation of the eye muscles can cause these muscles to become stiff and this may lead to strabismus and double vision. Thyroid eye disease is and example of such a condition
What are the problems associated with strabismus in adults?
Adults who previous had well aligned eyes and who suddenly develop strabismus, will almost certainly suffer from double vision. The double vision may only be present when they look in a particular direction or it may occur irrespective of where they are looking. This double vision can be very trouble-some as it may interfere with everyday tasks and could disqualify the them from driving.
In patients who are struggling to overcome strabismus and keep their eyes together, symptoms such as headaches, “eye strain” and intermittent double vision are common. These patients may have to tilt or turn their head in a certain direction to help control their strabismus. This compensatory head posture may cause neck and muscular problems.
Strabismus may be a sign of an underlying medical condition and any adult who suddenly develops strabismus should be seen by an Ophthalmologist who will be able to determine the cause of their strabismus.
In addition to affecting eye function, misaligned eyes can get in the way of normal eye-to-eye contact, communication skills and social interaction. This can lead to reduced self-confidence and many patients will often look down or away from the person to whom they are speaking to avoid eye contact. The person being spoken to may be uncertain which eye the patient is using and may be distracted from what the patient is trying to communicate. Such impairment of communication skills can lead to limited job (or job advancement) opportunities.
How is strabismus detected?
Strabismus may be noted by the patient themselves (especially if it is causing double vision) or by family and friends. Strabismus is often detected by an Optometrist during a routine eye examination or by a patient’s General Practitioner.
All patients with strabismus should be referred to an Ophthalmologist who will carry out a comprehensive eye examination in order to determine the exact nature of the strabismus and what the treatment options are.
What are the treatment options?
Strabismus can be treated in various ways. Depending on the individual case, treatment options include:
- Glasses in some case prescribing glasses can enable the patient to realign their eyes
- Prisms plastic prisms of the appropriate strength can be stuck on to the spectacle lenses to correct the misalignment of the eyes. These are particularly helpful in cases where the angle of the strabismus is small, if the strabismus is likely to resolve spontaneously (this is the case in many cases caused by circulatory problems) or if surgery is not possible. It may be possible to eventually incorporate this prismatic correction into the spectacle lenses themselves.