Strabismus can be congenital, but can generally occur at any age. Often there is no recognizable cause, but sometimes the squint is due to a serious underlying disease. The treatment of strabismus and its consequences vary depending on the age of the patient and the type of strabismus. Strabismus always needs to be clarified so that the correct diagnosis can be made and appropriate treatment can be given. No child is too young for an orthoptic and ophthalmologic examination.
Strabismus: Different forms
It is important to distinguish between the different types of squint. This diagnosis is carried out by the orthoptist.
Hetereophoria (latent or hidden strabismus)
Heterophoria is relatively common: an estimated 70-80% of people are affected, mostly schoolchildren or adults. They usually don’t notice anything, because the brain can compensate for small misalignments itself. Sometimes, however, this causes discomfort, especially if you are tired or stressed or work very long hours on your PC/laptop without interruption:
- Headache, often in the forehead area, increasing during the day
- Blurred vision
- Rapid fatigue when reading
- Occasional double images, blurring of images
For adults with heterophoria, optimal spectacle prescription is a prerequisite for any treatment. Depending on the size of the squint angle, prism glasses may be prescribed to provide relief. If the squint angle is too large, eye muscle surgery may be discussed.
The concomitant strabismus (strabismus concomitans)
Concomitant strabismus is almost always congenital or develops at preschool age.
Many babies give the impression that they are squinting inwards. In so-called pseudo-strabismus, the eyelid crease, which hides part of the palpebral fissure towards the nose (epicanthus), simulates an inward squint. Many parents report that they notice squinting in photos or that one eye ‘stops’ when looking sideways. With increasing age, this epicanthus recedes and the impression of squinting diminishes. It is important to distinguish this pseudo-strabismus from true strabismus. Strabismus does not fuse and always requires an orthoptic and ophthalmologic examination.
As strabismus usually occurs in young children or is congenital, the consequences are different from those in adults. Visual development takes place from birth until around the age of 8 to 10 and is most sensitive in the first few years of life. The child’s brain thus suppresses the visual impression of the squinting eye in the event of a misalignment in order to avoid the perception of disturbing double images. One consequence is that the visual acuity of the squinting eye becomes weaker, resulting in visual impairment (amblyopia). In the case of concomitant strabismus, spatial vision is impaired or non-existent. Some children with concomitant strabismus are more farsighted and require spectacle correction. This can have a positive effect on inward squinting. An examination of the eye is important to rule out a congenital or recent disease.
As a matter of principle, children should always have their lenses determined with eye drops (cycloplegia). More severe visual defects are corrected, as inward squinting can be reduced or even completely corrected by the glasses alone. If there is no good visual acuity on both sides after the spectacle prescription, a masking treatment is first carried out to improve any visual impairment (amblyopia). Surgical correction of strabismus is usually performed at kindergarten age. Rarely, eye muscle surgery should be performed quickly in order to maintain the acquired spatial vision.
Childhood strabismus occurs more frequently in families, e.g. between siblings, or if one of the parents also has strabismus. We therefore recommend that siblings of squinting children are examined at an early stage. Since strabismus in children is usually associated with visual impairment and should ideally be treated at preschool age, early detection is crucial. The earlier the visual impairment is discovered and treated, the better the chances of achieving full visual acuity with glasses and/or masking treatment and avoiding permanent damage.
Paralytic strabismus (strabismus paralyticus)
Strabismus occurs when diseases or injuries paralyze the eye muscles or the nerve. In contrast to strabismus, the mobility of the eye is restricted in one or more directions. This results in a misalignment of the eyes. This sudden onset form of strabismus usually affects adults, but children can also be affected. Typical symptoms are sudden double vision, which can lead to dizziness and nausea. Added to this is an incorrect spatial assessment. Some patients squint one eye or tilt their head to avoid seeing double. Strabismus can have serious causes. Patients are often referred to other departments at the USZ for further diagnostics. Depending on the cause, eye muscle paralysis and the resulting strabismus may regress. If the strabismus does not improve despite causal therapy, prism adjustment or eye muscle surgery should be considered.
Strabismus: Diagnosis with us
Our team of experienced orthoptists can diagnose strabismus as early as infancy, and visual acuity can also be determined using special tests (preferential looking method). Ophthalmologists and orthoptists can carry out a refraction test with eye drops to determine the strength of the spectacle lenses and perform an examination of the eye. In older children and adults, we can carry out precise and detailed measurement of the squint angle in all directions of gaze in the orthoptic department, which facilitates the diagnosis of ocular muscle paralysis. Our orthoptists and doctors are trained in the field of neuro-ophthalmology (eye and brain) so that strabismus can be recognized as a sign of a disease at an early stage and treatment can be provided. We attach great importance to interdisciplinary cooperation with other departments at the USZ, the children’s hospital and the rehabilitation centers.