Hemianopia is one of the neurological disorders they show us how vision is a complex operating process. We generally think that what we see enters through the eyes as light and is represented in the brain as a unit, after our nervous system takes over the unification of the information received in the “raw” format.
However, the sense of sight operates from a process which is not limited to collecting data and joining it, but which has a much more active role than it appears: it composes images which do not are not really the same as the eye-catching ones.
In fact, the mere fact of having a pair of these sense organs already necessarily makes it so, and hemianopia helps us understand this. Let’s see.
What is hemianopsia?
As far as we know, vision is one of the most important senses we have, but it’s also true that it can fail in a number of ways. Hemianopia is one of them.
As the name suggests, hemianopsia concerns the hemispheres, or rather hemicosis, which are the sides of our body divided by a vertical axis (i.e. the left or right sides) from our the nervous system. More specifically, hemianopsia it is blindness on one side of the visual field.
In other words, it is not that we cannot see through one eye and therefore our visual field narrows in the horizontal direction when one of its sides is narrowed; in one or both eyes has one of the two halves of the visual field ceased to exist
Hemianopsia may seem unusual and not as easy to understand as conventional blindness, but in reality it is always a neurological type disease that affects vision. Therefore, all of its associated symptoms are related to this type of problem: orientation problems, confusion about not finding a space, person or object, Feeling like you don’t know where you are, etc.
It is also possible that these symptoms are mixed with those of the accident or illness which in turn caused the hemianopsia, which, as we will see, can be caused by a wide variety of phenomena.
However, these symptoms also depend on the type of hemianopsia in question, as this disorder manifests itself in different ways.
The main types of hemianopia are based on a first basic classification: unilateral and bilateral hemianopia. In the first case, the alteration affects only one of the eyes, while in the second, it manifests as a vision that depends on both eyes.
In turn, bilateral hemianopia it can be homonymous, if the affected side in both eyes is the same, or heteronymous, If in each eye the affected side is different: in one, it affects the right, and in the other, the left.
Hemianopsia is usually caused by lesions caused by trauma, stroke and tumors, All structurally affect the nervous system.
However, in some cases this may be due to transient phenomena such as substance use or migraine headaches with aura, which can lead to temporary hemianopsias, with symptoms remitting very quickly.
The parts of the nervous system that are usually behind hemianopia are the optic chiasm or the last stretches of the optic pathways on their way to the thalamus: the optic ribbons.
Difference from heminegligence
It is possible to confuse hemianopsia with heminegligence, a neurological disorder that is also linked to hemicosis.
The main difference between the two is that heminegligence is not only affected by vision, But the experimentation of all the senses.
The second important difference is that in heminegligence the problem is technically not in the vision itself, but rather in the attention. Sensory data reaches the brainBut they are not treated as if they were relevant: they are “rejected”. Therefore, we saw that there is a kind of very meager notion of what happens to the ignored hemicos even though this information is not in the consciousness and the person believes they have not noticed anything, like this. has been seen in the experiments.
In the case of transient hemianopia, the intervention is limited to ensuring the well-being of the person until the effects disappear. Treatments aimed at intervening in non-transient hemianopsia they are of the type of neurological rehabilitation, Assuming a full recovery might not occur.
- Adel K. Afifi. (2006). Functional neuroanatomy: text and atlas. Mexico: McGraw Hill p. 324.
- Caramazza, A .; Hillis, AE (1990). “Spatial representation of words in the brain involved in studies of a patient with unilateral neglect.” Nature (Charter). 346 (346): pages 267-269.
- O’Neill, E., O’Connor, J., Brady, J., Reid, I. and Logan, P. (2011). “Prism of visual therapy and rehabilitation in the losses of the homonymous visual fields”. Optometry and Vision Sciences, vol. 88 (2).