Squint: Treatment, symptoms, advice and help
Strabismus or squint is malalignment of the eyes. Early detection prevents visual impairment.
Squint: Incidence, age and sex
It is a relatively common condition occurring in approximately 4% of children younger than 6 years. It may also occur in adults.
Signs and symptoms of squint: Diagnosis
Heterophoria refers to the latent tendency for the eyes to deviate. The eyes deviate only under certain conditions like fatigue, stress or during tests. Some degree of heterophoria is found in normal individuals and is usually asymptomatic. Heterotropia is malalignment of the eyes that is constant due to inability of fusion mechanisms to control the deviation.
Esophoria and esotropia:
The prefix eso is used to describe the inward deviation of eyes (commonly known as crossed eyes) and exo means outward deviation of eyes, wall-eyed being the lay term.
Hyperdeviations and hypodeviations designate upward ad downward, respectively, deviations of the eye.
Pseudo strabismus (pseudoesotropia):
It is the false appearance of strabismus when the visual axes are aligned accurately. This may be caused by a flat, broad nasal bridge, prominent epicanthic folds or narrow interpupillary distance. As the child grows, the bridge of nose become more prominent, the folds above the eyes get pushed outwards and the appearance of crossed eye disappears. Because true esotropia may develop in the child later on, the parents should be cautioned that reassessment is required if the cross eye does not improve.
Diagnosis is done by looking at the individual and by the following tests:
Corneal light reflex
The examiner projects a light source onto the cornea of both eyes as the child looks straight ahead. In straight eyes the light reflection appears symmetrical. In strabismus, it is asymmetrical. This test may not detect small angle or intermittent strabismus.
This requires the child's attention and cooperation, and consists of cover-uncover test and the alternate cover test.
The child is asked to look at an object about 6m away. As the child looks at the object, the examiner covers one eye and watches the other. If no movement occurs, there is no strabismus. After one eye is tested, the same is repeated on the other eye.
Alternating cover test:
The examiner rapidly covers and uncovers each eye, shifting back and forth from one eye to the other. If the child has ocular deviation, the eye rapidly moves as the cover is shifted to the other eye.
Causes and prevention of squint
In many cases of childhood squint, the reason why a squint develops is not known. In some cases of childhood squint (and most cases of adult squint) the squint occurs because of a disorder of the eye like refractive errors, cataracts and poor vision, eye muscles, brain or nerves.
A child would ignore the image coming from the deviated eye, and thus sees only one image. But in the process, he loses the depth perception. This suppression of the image from the deviating eye results in poor development of vision in this eye, which is known as amblyopia.
An adult cannot ignore the image from either eye, and therefore has double vision. This can be very annoying and may interfere with work. It also leads to reduced self-esteem because of the way their squint looks.
The primary goal of treatment is to eliminate or reduce the deviations as much as possible. Early treatment is more likely to be successful. Therapy may include the prescription of eyeglasses for children who have significant refractory errors and treatment of amblyopia with occlusion and penalization of the preferred eye. Surgery is then performed to align the eyes.