Visual impairment (amblyopia) – causes
Amblyopia is a decrease in visual acuity in one eye – less often in both eyes – despite the absence of pathological changes in the eyeball and visual pathway and with optimal correction.
Amblyopia is less commonly associated with corneal diseases, congenital cataract or eye injuries, it more often occurs as a result of strabismus and anisometropia (varicose vision – especially in the case of a defect called hyperopiaor, colloquially, farsightedness). It registers then errors in cooperation on the line brain – eyes: the brain favors only one of them, and the eyes, instead of cooperating, begin to compete, which makes one of them weaker (“lazy”). To simplify: we have a situation in which one of the eyes does not get involved in the vision process.
Visual impairment cannot be corrected by fitting glasses or contact lenses, by squinting or improving lighting conditions. Laser vision correction will also improve “only” the function of the eye – but will not improve the work of the brain, whose cooperation with the optical apparatus is indispensable in the process of correct vision.
Visual impairment due to strabismus
Strabismus-induced visual impairment is a situation in which impressions from the guiding (non-strabismic) eye dominate over those from the strabismic eye.
Muscular imbalances involving the oculomotor muscles usually lead to strabismus, while the positioning of the eye in an abnormal position causes the image to be formed in the eye not in the central area of the retina, but more peripherally – in an area where the density of photoreceptors is much lower. The brain remembers, fixes this imperfect image, and even when the strabismus is cured, this image remembered by the brain appears to us as the only possible one.
Visual deprivation vs. varifocality
The vision deficiency in varifocality comes from the fact that one of the eyes, for a period of time, was working for two, while the other eye did not make an effort to see as well as possible. Again: the brain remembers this inferior image, and even when the eye is corrected and there are no objective obstacles preventing it from seeing optimally, we will not see the image correctly. Why? This is due to improper processing by the brain. A good image can only be seen at the retinal level.
Visual impairment vs. astigmatism
The cause of visual impairment can also be astigmatism – e.g., a child may develop visual impairment in both eyes due to lack of exposure to the ideal retinal image.
Visual impairment due to obstruction of vision
An obstruction to vision should be understood as an obstruction within the eyeball itself – congenital cataracts or tumors inside the eyeball. These barriers prevent sufficient light from reaching the retina. A brain that cannot receive the correct stimulus will not learn the appropriate response to that stimulus.
When there is an obstruction to vision, we have no way for the visual pathway to develop properly between the retina and the visual cortex in the brain.
Even if one removes this obstacle, and this happens in early childhood, it is necessary to implement therapy and pleoptic, orthoptic, oculomotor exercises to support the next stages of binocular vision, as well as convergence and accommodation training.
