What is Hemianopia?
Hemianopia which is also sometimes referred to as Hemianopsia, is a visual disorder in which half of the visual field is affected and the person is able to see only half the things in his visual field and has complete blindness or decreased vision in the other half. Hemianopia is a term which originated from three different Greek terms viz. “hemi” meaning half, “an” which means without and “opsia” which translates to vision. So basically it means without half vision.
Sometimes when a person is suffering from severe migraine, he or she may experience temporary hemianopia but it is usually short lived. While the person suffering from permanent hemianopia experiences blindness in half his visual field permanently and this is usually due to brain injury or brain tumor.
Patients suffering from hemianopia tend to run into things and become easily surprised and agitated due to the sudden emergence of things and people in their visual field or so it seems to them. They trip or fall very easily and are, therefore, quite nervous of crowds and public gatherings.
Types of Hemianopia
Hemianopia can be of various types depending on which side of the visual field is being lost. It is broadly classified into the following types-
Homonymous hemianopia is a condition in which the same side of the visual field is lost in both the eyes. It can be left side or the right side depending on which side of the brain is affected. Our brain’s connection to the rest of the body is kind of crisscrossed. So the left optic tract on the left side of the brain controls right side of the vision in both the eyes. Similarly, right optic tract in the right side of the brain controls left side of the vision of both the eyes. So whichever side of the brain gets affected results in the loss of the vision of the opposite sides from both the eyes.
Heteronymous hemianopia is a type of hemianopia that can be described as the loss of the vision in different visual fields of the eyes. It can be further classified into different types:
When the blindness occurs in the field of vision that is closest to the nasal part in both the eyes, it is termed as binasal hemianopia. This occurs due to the presence of lesions or some damage to the lateral retinal nerve fibers which do not cross in the optic chiasm and convey information from the temporal retina. This results in loss of vision from the nasal side of both eyes.
Bitemporal hemianopia is the blindness or loss of vision from that side of both the eyes which is towards the temple or the outer side. This usually occurs due to the formation of lesions or damage to the optic chiasm area. Optic chiasm is actually the area near the pituitary gland where the nerves from both the eyes crisscross over each other to reach the opposite side of the brain.
Other Types of Hemianopia
There are some other types of hemianopia as well. Some of them are listed below:
This is, as the term indicates, a loss of vision in a quadrant or one quarter of the visual field. Which quarter of the vision is lost to blindness usually depends on which part of the brain got damaged. The loss of vision occurs in the part which is connected to the damaged part of the brain.
When the loss of vision occurs in the upper part of the visual field of both the eyes, it is termed as superior hemianopia.
If the loss of vision is occurring in the lower half of the vision field of the eyes, then it is called as inferior hemianopia.
Causes of Hemianopia
As mentioned above, hemianopia may occur due to severe migraine but that is only temporary. Other causes of permanent hemianopia include:
This may be due to an accident or a brain surgery causing injury or damage to some part of the brain resulting in hemianopia. Formation of lesions in different part of the brain can also be a cause of hemianopia.
Hemianopia can also occur due to a stroke. When the brain is not getting enough oxygen, it stops functioning properly resulting in a stroke which is a serious and dangerous medical condition, more often than not resulting into death. But if the patient survives, he suffers from various disorders, one of them being hemianopia.
Brain tumor can also be a cause of hemianopia. Formation of tumors in brain can lead to the brain being damaged or adversely affected resulting into hemianopia.
Treatment for Hemianopia
Treatment for hemianopia is not so much a treatment as it is a kind of rehabilitation. Different techniques for treating patients suffering from hemianopia are available nowadays. All of them are focused on enhancing a person’s perceptive, and somewhat his or her field of vision. But none of them can cure the disorder.
Doctors can choose to apply any of these techniques for treating hemianopia and sometimes even combine various treatments to achieve better results. Some of them are as follows:
Audio-Visual Stimulation Training
This is a program designed to improve the condition of the hemianopia patient using sound and light. In this treatment technique, both the affected and unaffected field of vision of the person suffering from hemianopia is stimulated using multi-sensory approach. It is especially effective treatment for homonymous hemianopia.
Explorative Saccade Training
It is also called scanning therapy. In this treatment therapy, patients who suffer from hemianopia are trained to make explorative saccades in that part of the visual field where their vision is lost, without moving their heads. Hemianopia patients are trained to use this technique in their everyday lives.
Optical Visual Span Expanders
It is actually some special types of eyeglasses in which a prism is mounted to increase the visual fields of hemianopia patients. Patient suffering from hemianopia combines the image provided by the prism to what he can actually see, which increases his vision field.
Visual Restoration Therapy
This technique for the treatment of hemianopia is available from NovaVision and uses a computer. It occurs in half an hour sessions where the patient suffering from hemianopia fixes his gaze on a point and then has to move his head whenever a light stimuli occurs in his field of vision. The computer records the data and after some time NovaVision adjusts the technique according to the data provided by the computer.
So these were some of the techniques that can be used to better rehabilitate the hemianopia patients and help them live as normal a life as possible.
- American Academy of Ophthalmology: “Hemianopia.” Source: https://www.aao.org/eye-health/diseases/hemianopia A reliable source providing information on hemianopia, its causes, types, and treatment techniques.
- National Institutes of Health: “Hemianopsia.” Source: https://rarediseases.info.nih.gov/diseases/7301/hemianopsia A comprehensive resource on hemianopsia, discussing its causes, symptoms, and available treatments.
- NovaVision: “Visual Restoration Therapy.” Source: https://www.novavision.com/vision-loss/restoration-therapy/ Information on visual restoration therapy for hemianopia, a treatment option offered by NovaVision.