The pupillometer is a pupillometry instrument that determines the width and light responsiveness of the pupils. Pupillometers are especially important before eye refractive surgery because they can determine the laser range on the cornea. Because pupil width is also relevant from neurological and psychological perspectives, pupillometry also helps these disciplines.
What is a pupillometer?
A pupillometer is a pupillometry instrument that determines the width and light responsiveness of the pupils. In pupillary diagnostics, the physician tests the pupils for width and light responsiveness. Pupillometry measures the pupil diameter with a high degree of accuracy. Special instruments are required for this purpose. One of these instruments is the pupillometer. This is an instrument that can measure pupil responsiveness. It primarily tests pupillary response to specific visual stimuli in the patient’s immediate visual field. In Colvard pupillometry, the pupil diameter can be read on the pupillometer from a built-in ruler. Modern devices measure and process the data digitally. In this way, laterally different pupil widths can be detected. Offset, constricted or dilated pupils can also be documented in this way. The Colvard pupillometer is used in computerized pupillometry, which provides accurate and easy-to-process measurements under both daytime and twilight conditions. In addition to this instrument, the physician needs a diagnostic light for pupillometry, which is already integrated in modern pupillometers.
Shapes, types and styles
The pupillometer is usually equipped with a light. The main difference between the models is the recording, processing and measurement of data. Modern pupillometers are usually computerized. They transmit the data to a computer for processing, where it can be easily compared and stored. Apart from pupillometers of pupillometry, there are also simple pupillometers for measuring interpupillary distance. Pupillometers for measuring interpupillary distance are designed for dimensions between 55 and 75 millimeters. The average distance is 63.5 mm. The measurement of the interpupillary distance may be necessary, for example, in connection with glasses. The glasses can only be aligned centrally on the visual axis and thus provide the patient with the highest possible benefit if these measurements are observed. In earlier times, the measurement of the interpupillary distance was performed by an ordinary ruler. However, the pupillometer has a much more accurate measuring power than this method.
Structure and operation
Modern pupillometers are digital pupillometers. They are usually battery-operated devices whose integrated lights can be adjusted to various light stimuli. Some of the devices carry a handpiece. Others have a footprint and are intended for positioning on a table. The devices are equipped with an eye piece at the head end and have some measurement tolerance. The patient places both eyes accurately on the device. During the measurement, the machine reads the pupil width under the influence of different light stimuli. Most of the devices are designed for bilateral measurements, but mononuclear measurement is also conceivable with the machines. Measurement accuracy is usually 0.5 millimeters per side. The result is output on a fully digital display. In addition to the reactivity to light, the extent and speed of the reaction on both eyes are usually measured. The uniformity of response in both eyes can be an equally relevant variable. In the computer, the results are evaluated immediately after the examination. The transmission of the measured values is usually digital. The measurement process depends significantly on the type of pupillometer. Simple pupillometers work fundamentally differently than digital devices.
Medical and health benefits
Pupillometry is most relevant for refractive surgery. These eye surgeries alter the overall refractive power of the eye and are intended to replace conventional corrections such as eyeglasses or contact lenses. Pupillometry can provide information about the size of the treatment zone. Twilight and night vision should not be affected by the procedure. The measurement data from pupillometers help to ensure this.The zone 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, mismatches may occur between the laser-treated zone of the cornea and the dilated pupil diameter at twilight, because if the pupil exceeds the treated corneal area, the incident light will only be blurred. Thus, patients are blinded in the dark or see double. For this reason, pupillometry is one of the standardized examinations prior to refractive procedures such as laser treatments. Pupillometry using a pupillometer also helps with general assessments of vision. High light exposure physiologically narrows the pupil. Low light dilates it so that the eye can still receive enough light to see in the dark. In classical ophthalmology, the measured values are also used for general assessment due to these correlations. For example, ophthalmologists used the values to determine whether the pupils dilate sufficiently in the dark to take in enough light. This determination allows conclusions to be drawn about the ability to see at night. Since mental and neurological contexts can also influence pupil diameter, pupillometry using pupillometers is becoming increasingly relevant in these medical fields as well.
