What is strabismus (squint)?
Strabismus (also known as squint) is a common eye problem in children and adults. It refers to a misalignment of the two eyes. Some people may also call it a “lazy eye” or an “eye turn”.
The prevalence in the community of any type of squint is about 3%, i.e. 3 in 100 people.
Strabismus has a significant functional and psychosocial impact on people, and it can be treated. Dr Parth Shah has experience in treating all types of strabismus, including performing eye muscle surgery. He developed this specialised expertise and surgical skill by working with world-renowned specialists at centers in Australia, the UK, and the USA. https://www.drparthshah.com.au/parth-shah/
Dr Parth Shah performs eye muscle surgery for children and adults.
Types of strabismus: Esotropia, Exotropia, Hypertropia, Hypotropia
Strabismus can be intermittent or constant. The terminology used to describe the strabismus is based on the direction of the misaligned eye.
- A convergent misalignment (inward turn) is an esotropia.
- A divergent misalignment (outward turn) is an exotropia.
- When the eye is higher than the other, it is a hypertropia.
- When the eye is lower than the other, it is a hypotropia.
Most forms of intermittent strabismus can become more apparent can occur in certain situations, e.g. fatigue, illness or intoxication.
Signs and Symptoms of Strabismus
When the eyes are misaligned and looking in different directions, double vision can result. Infants and children with strabismus can ignore (“suppress”) the double image because the brain is able to adapt to the misalignment. However, these children will not develop normal “binocular” or “3-D” vision, as their brain did not learn to use both eyes together. Gross and fine motor development can be reduced. Children with strabismus can start to favour one eye over the other (amblyopia), which needs to be monitored and treated.
Adults with new strabismus can suffer debilitating symptoms:
- Double vision
- Visual confusion
- Eye “strain” and headache
- Reduced field of vision
- Neck pain from turning or tilting the head to avoid double vision
There are many negative psychosocial impacts of strabismus on daily interaction. Studies have demonstrated that patients with strabismus have a reduced quality of life. Children can be bullied at school due to the appearance. Adults with strabismus can experience reduced self-esteem, and difficulties with social interactions both socially and professionally. This is because it can seem like they are not maintaining eye contact when one eye drifts in or out.
Myth & Facts about Strabismus (squint)
Myth 1: Squint in small children can go away on its own
Fact 1: A newborn and young infant until six months of age can have an intermittent squint. After this age, it is uncommon for a squint to disappear on its own. This is a popular belief harboured by many parents and re-enforced by some doctors too. In older children, a delay in diagnosis and treatment could potentially lead to reduced vision in the child. Any constant strabismus should be evaluated by a paediatric ophthalmologist.
Myth 2: Squint is just a cosmetic problem
Fact 2: In addition to strabismus being a cosmetic problem, it is often also a significant functional problem. This is because a squint can lead to reduced vision (amblyopia) and reduced field of vision. Early treatment of squint may be recommended to prevent deterioration of vision and binocularity – not only to straighten the eyes for reconstructive reasons.
Myth 3: There is no good treatment for squint
Fact 3: Depending on the type of squint, there are many treatment options like glasses, prisms and eye muscle surgery. Any one or a combination of these treatment modalities may have to be used depending upon the case. Treatment of squint may be long term and generally associated with successful results. Squint can be treated at any age, even in adults.
Myth 4: Squint surgery will cause damage to the eye
Fact 4: Eye muscle surgery is generally very safe. It is an extraocular procedure, i.e. it does not involve opening or entering the eye like in cataract surgery. The extraocular muscles on the white of the eye (sclera) and weakened, strengthened or moved to a different location. A surgeon will discuss the specific risks and benefits for each individual patient.
Myth 5: Squint will recur after surgery
Fact 5: This is a common fear in patient’s and parents’ minds, and prevents them from going in for the surgery in the first place. With proper pre-operative evaluation and operative technique, the chances of recurrence in childhood squint are low. If eye muscle surgery is recommended, the risks of recurrence is outweighed by the benefits to the patient. Recurrence may occur many years after surgery, and there may be non-surgical and surgical options to treat this.
Causes of Strabismus
There are many possible causes of strabismus. It may be a problem with one of the six muscles responsible for eye movement, one of the three nerves that control those muscles, or an issue with the brain
In childhood, strabismus can occur in healthy children with normal eyes. The eyes are misaligned due to an abnormality in the central coordination of eye movements. The exact mechanism is poorly understood. Examples include infantile esotropia and intermittent exotropia syndrome.
Another common cause of esotropia in infants is accommodative esotropia. This is when the child is has a focusing issue, namely long-sightedness. This means that the child needs to use their eye’s focusing system to see clearly, which leads to an esotropia. Prescribing glasses to relax the long-sightedness can partially or completely resolve the strabismus. However, when the child does not wear glasses, the eyes will be turned.
Poor vision in one or both eyes can lead to strabismus in children and adults. Poor vision may be due to a focusing problem, cataract or retinal problem. This leads to the brain not being able to “fuse” the images from the two eyes, and the poorer seeing eye can drift in or out.
Adults can have strabismus either from an issue that started in childhood, or one that arises in later life.
Paralysis of any of the three delicate nerves that control eye movement will cause an imbalance in the eye position. This can occur, for example, due to impaired blood supply (stroke), or something pressing on the nerve (aneurysm, tumour).
Patients with a problem affecting the eye socket can have strabismus due to eye muscle imbalance. Examples of this include a fracture of one of the walls of the eye socket and thyroid orbitopathy (Graves disease).
Diagnosis and Treatment of Strabismus
An assessment and diagnosis of strabismus is important to guide management decision making and can be performed in specialised ophthalmology strabismus clinics where Dr Parth Shah works. This includes assessment of vision, checking for refractive error (glasses) and examining for cataract and retinal pathology. The type and size of the strabismus is measured accurately using prisms and instruments for checking binocular (“3-D”) vision.
There are several treatment options for strabismus with good success rates.
The best treatment option will depend on a number of factors including patient symptoms, age, underlying diagnosis and previous treatment.
Any reversible disease process needs to be managed appropriately, e.g. cataract surgery or treatment of thyroid overactivity (Graves disease).
In children, focusing error and amblyopia need to be managed simultaneously with the strabismus. Glasses and patching may be necessary.
Incorporation of prism into glasses may be suitable in some types of small angle strabismus in adults experiencing double vision.
Botulinum toxin can be injected directly into an extraocular muscle to induce temporary paralysis. It is used in the treatment of strabismus where surgery is contraindicated, or in situations where future improvement is predicted
Eye muscle surgery can be performed for functional or reconstructive purposes. The muscles are permanently weakened, strengthen or moved to a different position. Surgery is not a final or last resort treatment option for strabismus, and in many cases, it may be the best or only suitable option.