Pupillometer

The Pupillometer is an instrument of pupillometry that determines the size and light responsiveness of the pupils. Pupillometers are especially important before refractive surgery on the eye because they can determine the laser area on the cornea. Since the pupil size is also relevant from a neurological and psychological point of view, pupillometry also helps these disciplines.

What is a pupillometer?

During the pupil diagnosis, the doctor examines the pupils with regard to their size and the ability to react to light. Pupillometry measures the pupil diameter with great accuracy. Special instruments are necessary for this. One of these instruments is the pupillometer.

This is a device that can measure pupil responsiveness. It primarily tests the pupillary response to certain visual stimuli in the patient's immediate field of vision. With Colvard pupillometry, the pupil diameter can be read off a built-in ruler on the pupillometer. Modern devices measure and process the data digitally. In this way, pupil widths that differ on the sides can be recognized. Displaced, narrowed or dilated pupils can also be documented in this way.

The Colvard pupillometer is used in computer-aided pupillometry, which enables an exact and easy-to-process measurement under both day and twilight conditions. In addition to this instrument, the doctor needs a diagnostic light for pupillometry, which is already integrated in modern pupillometers.

Shapes, types & types

The pupillometer is usually equipped with a light. The main difference between the individual models is the way in which the data is recorded, processed and measured. Modern pupillometers are usually computerized. They transfer the data to a computer for processing, where it can be easily compared and stored.

Apart from the pupillometers used in pupillometry, there are also simple pupillometers for measuring the interpupillary distance. Pupillometers for eye distance measurement are designed to measure between 55 and 75 millimeters. The average distance is 63.5 mm. The measurement of the interpupillary distance may be necessary in connection with glasses, for example. The glasses can only be aligned centrally on the visual axis if these dimensions are observed and thus provide the patient with the greatest possible benefit.

In earlier times, the measurement of the interpupillary distance was carried out by an ordinary ruler. The pupillometer, however, has a much more precise measuring force than this method.

Structure & functionality

Modern pupillometers are digital pupillometers. They are mostly battery-operated devices whose integrated lights can be adjusted to different light stimuli. Some of the devices carry a handpiece. Others have a footprint and are intended to be placed on the table.

The devices are equipped with an eye piece at the head end and have a certain measurement tolerance. The patient places both eyes exactly on the device. During the measurement, the machine reads the pupil size under the influence of various light stimuli.

Most of the devices are designed for bilateral measurements, but mononuclear measurements are also conceivable with the machines. The measurement accuracy is usually 0.5 millimeters per side. The result is shown on a fully digital display. In addition to the ability to react to light, the extent and speed of the reaction are usually measured in both eyes. The evenness of the reaction in both eyes can be an equally relevant quantity.

The results are evaluated in the computer immediately after the examination. The measured values ​​are usually transmitted digitally. The measurement process depends significantly on the type of pupillometer. Simple pupillometers work fundamentally differently from digital devices.

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Medical & health benefits

Pupillometry is particularly relevant for refractive operations. These eye operations change the overall refractive power of the eye and are intended to replace conventional corrections such as glasses or contact lenses. The pupillometry can provide information about the size of the treatment area. The operation must not impair vision at dusk or at night. The measurement data from pupillometers help ensure this.

The area to be treated must at least correspond to the pupil diameter in twilight so that night vision is possible. If the pupil diameter is calculated incorrectly, there may be disproportions between the laser-treated zone of the cornea and the widened pupil diameter at twilight, because if the pupil exceeds the treated corneal area, the incident light is only blurred. Patients are blinded in the dark or see twice.

For this reason, pupillometry is one of the standardized examinations before refractive interventions such as laser treatments. Pupillometry using a pupillometer also helps with general assessments of eyesight.

High exposure to light physiologically narrows the pupil. It expands little light so that the eye can still absorb enough light to see even in the dark. In classic ophthalmology, the measured values ​​are also used for general assessment based on these relationships. For example, ophthalmologists use the values ​​to determine whether the pupils dilate enough in the dark to absorb enough light. This determination allows conclusions to be drawn about the ability of night vision.

Since mental and neurological relationships can also have an influence on the pupil diameter, pupillometry using the pupillometer is becoming more and more relevant in these medical fields.