Strabismus is a vision disorder characterized by the misalignment of the eyes, which are not oriented synchronously. Thus, it is not only an aesthetic anomaly but, in most cases, is also a disorder that may be more or less severe. For this reason, it is best to schedule an eye examination as soon as possible to assess the situation.
The orthoptist is the main technical figure to assist ophthalmic physicians. It is also involved in the diagnosis and treatment of eye alignment problems.
Strabismus: Why it arises
Strabismus is a vision disorder characterized by the misalignment of the eyes, which are not oriented synchronously: One eye, in fact, points in a different direction than the other, an asynchrony that generates a splitting of the perceived image.
Each eye gives the brain a distinct image as if it were “a camera.” When the eyes are correctly aligned, the brain combines the two images while providing stereopsis: depth perception.
In those with strabismus, one eye may look straight ahead. The other deviate inward – convergent strabismus, or exotropia, respectively – outward – divergent strabismus, exotropia – or upward or downward – vertical strabismus, hypertropia, and hypotropia, respectively. This defect hinders proper binocular vision.
If left undiagnosed and untreated, strabismus in younger patients can progress to amblyopia: The child tends to suppress one of the two images, using only one eye, thereby losing stereoscopic vision, that is, the sense of depth.
If the suppression is constant, the deviated eye is no longer used, as it creates confusion, and visual acuity does not develop adequately.
Strabismus can occur at any age, and not only in pediatric age.
In adulthood, the onset of strabismus causes diplopia, that is, double vision. The brain, after getting accustomed to using the images from both eyes, cannot suppress the image from the deviated eye, and the effect is severely disabling.
The leading causes of strabismus, although not always known, are:
- Genetic predisposition;
- Eye diseases that prevent the eye from seeing properly and fixing objects, such as cataracts or eyelid ptosis, for example;
- Refractive defects (hyperopia, myopia, astigmatism). An uncorrected visual defect can prevent good vision and hinder the development of eye movement;
- Cerebral paresis. it is the brain that coordinates eye movements, so strabismus is quite common in cases of brain disorders;
- Paresis of one or more eye muscles;
- Underlying conditions such as neurological diseases, trauma, diabetes, hypertension, etc.
When is it good to consult a specialist?
An eye examination and orthoptic examination are essential to obtain a correct diagnosis.
Children should, therefore, be examined periodically from the earliest months to assess vision and detect any strabismus.
The diagnostic procedure includes:
- Comprehensive eye examination with visual acuity examination;
- Corneal light reflex examination;
- Cover test;
- Stereopsis examination (three-dimensional vision ability);
- Ocular motility study.
In the case of cranial nerve palsy, diagnostic imaging examinations, such as computed tomography (CT) or magnetic resonance imaging (MRI), are required.
The eye and its anatomical structures can be examined precisely thanks to new instrumentation, resulting in accurate diagnoses and appropriate treatments for each situation.
Strabismus: How is it treated?
The treatment approach to strabismus can be surgical and non- surgical.
The non-surgical approach mainly consists of four options:
- Correction of any refractive defect;
- Occlusion of the eye that sees best to force the use of the other, weaker eye. This therapy involves covering the “strong” eye for a few hours during the day, perhaps with an eye patch tampon or an opaque lens, so the “lazy” eye can recover its visual ability. Once equal visual acuity is achieved in the two eyes, the occlusion is gradually reduced while monitoring that the result obtained remains stable over time;
- Prismatic lenses, helpful in restoring binocular vision to the patient. These specific lenses, once applied to the eyeglass, help the eye to change its position;
- Orthoptic exercises, which can reduce muscle imbalance in the eyes.
Where non-surgical procedures are not effective, surgical intervention is needed.
Surgery can correct the imbalance of the eye muscles to maintain a situation as close to normal as possible.
In some cases, only the muscles of the deviated eye can undergo surgery. In others, surgery will be performed on the muscles of both eyes to allow a realignment as precise as possible and to correct the ability of one or more eye muscles to act.
However, several operations may be necessary to achieve the desired result.