What causes strabismus?
We cannot speak of a single etiology for strabismus. The loss of ocular parallelism and binocular vision can be classified into different types and their reason, too. From the congenital and hereditary cause, which determines a lack of oculomotor coordination, through the malformation of a certain muscle or muscles, or nuclei of the central nervous system, to trauma or a small cerebral infarction in an adult, or the so frequent convergent strabismus in the hypermetropic child.
All this can determine the appearance of a strabismus of different type and degree, with different treatment.
How does it affect vision?
Before commenting on the visual consequences, it should be noted that there is another aspect to highlight for the psycho-affective development in the child or the relationship with the environment in the adult.
A strabismus, contrary to what is usually thought, does not only produce an aesthetic alteration. In addition to the visual disorder, the fact of losing the normal appearance with parallel eyes, alters the fluency in interpersonal relationships that produces a psychological disorder, and can significantly reduce self-esteem, so much so, that its surgery should be considered as reconstructive, without considering the visual benefits it entails.
As for the visual consequences, it is essential to distinguish whether it occurs in a developing child or in an adult.
In the child, if visual learning has not yet been developed, there is a high risk of amblyopia, the so feared lazy eye, and also the impossibility of developing binocular vision, which gives us the sensation of relief.
In a child of a certain age or in an adult the first consequence is double vision and superimposition of images, an extremely disturbing situation that, although in a child it may disappear in a few hours, in an adult it may persist for life if left untreated.
Does it have a solution in adults? What is the treatment in children and adults?
It is a very complex subject, all branches of ophthalmology specialization. It depends on many factors, visual acuity of both eyes, whether or not there is binocular vision or diplopia, which is the dominant eye; the graduation, fundamental in children and very important in adults.
In these, the situation can be improved in a high percentage of cases, giving better visual quality or curing diplopia and/or recovering visual parallelism.
The treatment almost always involves the exact graduation of both eyes, occlusion to improve the vision of each eye in children and often surgery of the extraocular muscles.
In children, we must first of all take care of the vision of the eyes, preventing or curing amblyopia, with glasses and occlusions. In addition, restoring eye parallelism may require surgery, although nowadays it is sometimes treated with botulinum toxin injections, with variable results. Whether it is a simple horizontal strabismus, accommodative or not, or there are vertical alterations, the extent and form of presentation, among other factors, will determine the treatment guideline.
What are the risks involved in extraocular muscle surgery?
Since extraocular muscle surgery does not act on the eyeball, but on the sheaths that cover it and the muscles themselves, the risk to vision is practically nil.
The risks are those common to any surgery, infection, bleeding or undesired outcome of the surgery. Even so, the percentage of good results far exceeds the risks inherent to surgery.
The risk of postoperative double vision always arises in adults, but it is rare for this to occur, and even rarer for it to remain in time.
What is the surgical treatment?
Surgical action on the muscles may include shortening (resection), retraction (weakening) and also modification of the action by changing the position of the insertion of the muscles on the surface of the eyeball.
It can be performed if minimal surgery is required, under local anesthesia; in children it should always be performed under general anesthesia and also when surgery is performed on previously operated patients or patients with scarring or restrictive problems.