BackgroundAn objective and noninvasive examination of pupil size variability can be used to assess the activity of the autonomous nervous system. We designed a system that enables binocular, fast, and accurate recordings of different types of pupil variabilities, which are synchronous with other biosignals. This type of measurement system is needed to extend the scope of pupillometry applications.MethodsIn the proposed system, the left and right eyes are independently and interchangeably illuminated to generate alternating images, which are successively acquired by a single camera. The system is composed of four functional modules: the image acquisition module, the image processing unit, the light stimulator, and the controller. The proposed image processing algorithm approximates the shape of the pupil using the best-fit ellipse. The user control panel (controller) precisely sets the stimuli parameters and controls the entire measurement procedure.ResultsThe computer-based binocular system records the pupil size during the pupil light reflexes (direct and indirect) and spontaneous pupil size fluctuations, at a sampling rate up to 75 Hz, with a resolution better than 0.02 mm. Our initial laboratory tests confirmed that the new system is fast and precise (system accuracy better than 0.5% and repeatability better than 4%).ConclusionsThe proposed system’s unique geometry and construction, and the method it uses to detect images from each eye, allows us to monitor the right and left eyes using a single camera with no overlap between the images. The system does not require a very experienced operator, because it is relatively simple and easy to use. Importantly, it is comfortable for the subjects. Additionally, the presented system can operate with other bio-measurement systems using a synchronous signal. These system capabilities can expand the scope of pupillometry research applications.

Ocular information was observed during a set of dementia tests involving participants with Alzheimer's Disease (AD), with a mild level of cognitive impairment (MCI), or in a control group. The number of participants was 26. Features of changes in pupil size and in the central position of both eyes of participants of all three types were compared. There are significant differences in some of the metrics between the types, in earlier test sessions. The possibility of classification was confirmed using the extracted features, and the contributions of some features were examined.

A procedure for detecting cognitive impairment in senior citizens is examined using pupil light reflex (PLR) for chromatic light pulse and a portable measuring system. Features of PLRs of blue and red light pulses are compared. PLRs of elderly subjects were studied in order to develop a procedure for detection of the symptoms of cognitive function impairment using a dementia evaluation test. PLRs of both eyes were measured using blue and red light pulses aimed at either of the two eyes. The features of PLR waveforms for each eye were remained in comparable level for every group of participant. Three factor scores were calculated from the features, and a classification procedure for determining the level of dementia in a subject was created using regression analysis. As a result, the contribution of factor scores for blue light pulses according to a participant's age was confirmed.

A procedure for detecting cognitive impairment in senior citizens is examined using pupil light reflex (PLR) to chromatic light pulses and a portable measuring system. PLRs of both eyes were measured using blue and red light pulses aimed at either of the two eyes. The symptoms of cognitive function impairment were evaluated using a conventional dementia test during clinical surveillance. The extracted features of observed PLR waveforms for each eye remained at a comparable level for every group of participants. Three factor scores were calculated from the features, and a classification procedure for determining the level of dementia in a subject was created using regression analysis. As a result, the contribution of factor scores for blue light pulses on both eyes according to a participant's age was confirmed.