Dorothy FarrarVisual field measurement
When measuring the field of vision , ophthalmology uses a diagnostic method to determine the patient’s field of vision. The field of vision is the space that is perceived by the eye without the gaze straying from a centrally fixed point. Perimetry is used to detect cataracts and other disorders at an early stage.
What is a visual field measurement?
The visual field measurement provides information about optical perception without moving the eye . A distinction is made between the measurement of the monocular field of view and the binocular field of view. This means the field of vision of one or both eyes.
The normal aging process causes the size of the field of vision to decrease, as can certain eye diseases. The simplest way of measuring the visual field is finger perimetry, which is often carried out by doctors as part of routine examinations.
In addition, other methods are common, which provide more accurate results, but also require special equipment.
application and function
Perimetry is used routinely in some cases. The visual field measurement is carried out during certain aptitude tests or is used to make statements about the fitness to drive of the person concerned. Even those who suffer from glaucoma or cataracts are regularly monitored and, in this context, subjected to continuous visual field measurements. If unclear visual disturbances occur in a patient, these can have various causes.
A visual field measurement is indicated if the patient suffers from night blindness , suddenly finds it difficult to read or has disorientation. With glaucoma , the increased internal pressure of the eye leads to damage to the nerve fibers and the field of vision is increasingly restricted. This process remains unnoticed over a longer period of time and therefore a relatively advanced glaucoma is usually detected by a visual field measurement.
Other causes of a restricted field of vision can also be a retinal detachment or diseases of the “yellow spot”. Here, the tissue of the retina is damaged and this usually leads to visual field defects in the central area.
The procedure is also used for damage to the visual pathways, which can be caused by trauma, a stroke , aneurysms or a brain tumor .
methods and procedures
There are different methods of measuring the field of vision. The simplest form is finger perimetry, which does not require any tools. The doctor sits opposite the patient and uses his finger movements to determine how far these are perceived by the patient. The patient is instructed to fixate on a fixed point and not to move his eyes.
The principle remains the same for the other measuring methods. The patient fixes on a fixed point and informs the doctor when he perceives a signal.
A distinction is made between computer-controlled and kinetic perimetry. In both methods, the patient sits in front of a screen and indicates when they see a light signal on the screen. With the computer controlled method, the flashes of light appear random. With the kinetic variant, the light signals migrate from the outer edge to the center of the screen.
What does the patient have to consider?
It is not necessary to prepare for a visual field measurement. The method is completely painless and no complications are to be expected. However, perimetry, which is supposed to deliver concrete results, requires the cooperation of the patient. They should be open to the method and have sufficient stamina and concentration.
Many patients find the method time-consuming and tiring. It’s a simple and painless way to diagnose a wide range of vision problems. The patient should keep this in mind and follow the test conscientiously and persistently.
With a computer-controlled visual field measurement, the person concerned has to be prepared to sit in front of a screen for about 20 minutes and fixate on a fixed point with their eyes. When a light flashes on the screen, press a button as quickly as possible.
Follow-up care is not required. However, in the case of certain eye diseases or suitability tests for pilots or in road traffic, regular measurement of the visual field is aimed at.
process and implementation
A visual field measurement is always carried out for one eye at a time. The patient’s head rests on a chin and forehead rest in front of the examination device. In order to be able to indicate promptly when he notices flashes of light, the patient holds a signal button in his hands.
In the kinetic field of view measurement, the subject sits in front of a hemispherical screen and directs their eye to a central point. The doctor sits on the opposite side of the machine and observes the position of the patient’s eye through a telescope. With the help of a mechanical lever system, light marks are generated that move from the edge of the hemisphere to its center.
Based on the signals sent out by the patient, the doctor creates a graphic that can be used to clarify the measurement result. The computer-controlled visual field measurement works in a similar way. The difference is that the light signals are not generated by the doctor himself, but by the computer. The light marks can be changed in their brightness and appear at random points.
This method can also be used to localize minor defects in the visual field. The evaluation is carried out using numerical values or shades of gray visible on the printout.
Self-service or health insurance – who will bear the costs?
If a patient has noticeable vision problems and therefore consults a doctor, the costs for the visual field measurement are covered by the statutory health insurance funds. Perimetry is also part of the statutory health insurance services as part of the regular examinations of pilots, professional drivers and other special professional groups.
The examinations are often carried out by the company doctor. If he lacks the appropriate technology, he will be referred to a specialist.
However, the visual field measurement is not recognized as a preventive examination. In the context of the early detection of visual disorders, the health insurance no longer pays for several years. In this case, the patient has to dig into his own pocket. The costs are around 15 euros.
Risks, dangers and complications
The visual field measurement is an examination that has no side effects. In addition, the treatment is completely painless. However, the patient is encouraged to actively cooperate. So it is important to keep your eye on a certain point during the measurement and to concentrate on the light signals that appear and to transmit them to the doctor as promptly as possible by means of a signal generator.
It is an advantage if the patient appears awake and alert on the day of the test, as the test result is highly dependent on the patient’s cooperation.
Hello and welcome to my Health Guide & Encyclopedia! My name is Dorothy Farrar, and I'm the founder and main author of this platform.
My passion for health and wellness started at a young age when I became interested in the connection between the food we eat and the way we feel. This fascination led me to study nutrition and dietetics in college, where I learned about the importance of a balanced diet and the impact of various nutrients on the body.