What is hemianopsia?
Hemianopsia or hemianopia is a vision impairment that can occur, for example, after a stroke, brain haemorrhage, brain surgery or tumour disease. It is caused by a lesion in the course of the visual pathway and results in a unilateral or bilateral restriction or loss of the visual field. The visual field is the area that can be seen when looking straight ahead with both eyes and includes both the central and peripheral fields of vision. Often, hemianopia is limited by the vertical midline of the eye and usually occurs on both sides of the eye; in rare cases, only one eye is affected. Generally, two forms of hemianopsia are distinguished: homonymous and heteronymous hemianopsia.
We speak of right or left homonymous hemianopsia when both eyes on the same side are affected. This occurs when there is damage to the visual pathway or visual centre in only one half of the brain. In this case, the person can only see one side of the normal field of vision, either the left or the right. This is noticeable in everyday life, for example, when the patient only eats one half of his or her plate, but leaves the other half empty. In heteronymous hemianopsia, both eyes are affected. The defect affects the outer sides of the field of vision, which is why it is called blinkered vision.
➤ The suffering caused by hemifacial blindness is often high, as those affected can no longer see people and objects well in the damaged area of the field of vision.
The unfamiliar restriction of vision can be confusing, patients find it difficult to find their way around on their own and often feel insecure in general. As severe as the limitations associated with hemianopsia, treatment for vision loss can be promising.
In the case of hemianopsia, there are various therapeutic approaches that aim either at the partial restoration of the visual faculty (restitution training) or at least at improved search movements in the affected visual field and thus at the best possible handling of the existing impairments (compensation training). In order to restore vision at least partially, restitution training uses visual light, colour and shape stimuli. However, this therapy method has the disadvantage that there is little or weak scientific evidence to prove its effect. In addition, restitution training is very expensive.
Compensation training, on the other hand, takes a completely different approach by specifically training the eye muscles. In independent exercises or together with trained therapists such as neuropsychologists or occupational therapists, computer-assisted programmes are used to focus on specific points as well as targeted eye movements and search strategies. The aim of the saccade training is to improve the sense of orientation of those affected by hemianopsia and to offer them more security in everyday life.
This eye training takes place either under therapeutic guidance or in independent exercises at home. With a therapist, it can include strategies such as working with paper and pencil, crossing out words or numbers, or hands-on walks where the person is asked to look for specific objects in the area of their impaired vision. In addition, there are computer programmes such as the saccadic training, which train the eye muscles with the help of on-screen exercises. This involves, for example, single- to multi-digit numbers as well as letters that appear on the screen. The patient has the task of touching these with the mouse and is rewarded auditorily and visually each time a number or letter is found. At the end of a task, when all numbers or letters have been touched, the patient's speed in solving the task is evaluated.
What is the benefit of therapy?
The success of saccadic training depends very much on the individual course of the disease, the extent and the form of the hemianopsia. In general, the sooner therapy is started after the onset of hemianopsia, the higher the chances of a significant and lasting improvement.
➤ Since it is basically a training of the eye muscles, saccade training can be started at any time and still has great success even in people who have been suffering from hemianopsia for 10 years.
To scientifically prove the success of saccade therapy and make it more measurable, scientists are calling for more studies Although this form of therapy has already shown success in practice and scientists have already found positive changes, further high-quality randomised-controlled trials are needed to confirm the results so far