Measurement of pupil reactivity using fast pupillometry

Hachoł, A.; Szczepanowska-Nowak, W; Kasprzak, Henryk T.; Zawojska, I; Dudzinski, A; Kinasz, R; Wygledowska-Promienska, D

doi:10.1088/0967-3334/28/1/006

Cited by 21 publications

(10 citation statements)

References 44 publications

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“…As random fluctuations whose causes are still unknown (UKAI; TSUCHIYA; ISHIKAWA, 1997), it is currently not possible to define a physiologically-based model for hippus. The hippus effect was visually approximated by adding some small random variations to the light intensity (between 10 −0.3 and 10 0.3 Blondels), to induce small variations in the pupil diameter (of the order of 0.2 mm (HACHOL et al, 2007)), in the frequency range of 0.05Hz to 0.3Hz. This significantly improves the realism of the resulting simulations and animations in indoor scenes.…”

Section: Modeling Individual Differencesmentioning

confidence: 99%

Photorealistic models for pupil light reflex and iridal pattern deformation

2009

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We introduce a physiologically-based model for pupil light reflex (PLR) and an image-based model for iridal pattern deformation. Our PLR model expresses the pupil diameter as a function of the lighting of the environment, and is described by a delay-differential equation, naturally adapting the pupil diameter even to abrupt changes in light conditions. Since the parameters of our PLR model were derived from measured data, it correctly simulates the actual behavior of the human pupil. Another contribution of our work is a model for realistic deformation of the iris pattern as a function of pupil dilation and constriction. Our models produce high-fidelity appearance effects and can be used to produce real-time predictive animations of the pupil and iris under variable lighting conditions. We assess the predictability and quality of our simulations through comparisons of modeled results against measured data derived from experiments also described in this work. Combined, our models can bring facial animation to new photorealistic standards.

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Section: Modeling Individual Differencesmentioning

confidence: 99%

Photorealistic models for pupil light reflex and iridal pattern deformation

2009

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“…A longitudinal comparison of the objective data obtained by AP is possible, and this allows the surgeon to obtain better information regarding neurological alterations. AP has shown greater precision and accuracy than MP examination in investigations of trauma, ICU, and ophthalmology patients 13–15. In this study, we compared AP and MP for pupil assessment in patients with LT or hepatic surgery.…”

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confidence: 99%

Clinical utility of an automated pupillometer for assessing and monitoring recipients of liver transplantation

Yan

Liu³

et al. 2009

Liver Transpl

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Pupil examination has been used as a basic measure in critically ill patients and has great importance for the prognosis and management of disease. An automated pupillometer is a computer-based infrared digital video system by which the accuracy and precision of the pupil examination are markedly improved. We conducted an observational study of pupil assessment with automated pupillometry in clinical liver transplantation settings, including pretransplant evaluations and posttransplant surveillance. Our results showed that unconscious patients (grade 4 hepatic encephalopathy) had a prolonged latency phase (left side: 283 Ϯ 80 milliseconds; right side: 295 Ϯ 96 milliseconds) and a reduced pupillary constrictive ratio (left direct response: 0.23 Ϯ 0.10; left indirect response: 0.21 Ϯ 0.07; right direct response: 0.20 Ϯ 0.08; right indirect response: 0.21 Ϯ 0.08) in comparison with normal and conscious patients. After liver transplantation, the recovery of pupillography in these patients was slower than that in conscious patients. However, the surviving recipients without major complications all had a gradual recovery of pupillary responses, which occurred on the first or second posttransplant day. We also reported 4 cases of futile LT in the absence of pretransplant pupillary responses and other pupillary abnormalities revealed by automated pupillometry in our study. In conclusion, patients with grade 4 hepatic encephalopathy had a sluggish pupil response and a delayed recovery pattern after LT. An automated pupillometer is potentially a supplementary device for pretransplant screening and posttransplant monitoring in patients undergoing LT, but further prospective studies are required. Liver Transpl 15: 1718-1727, 2009. © 2009 AASLD. Received March 16, 2009 accepted August 11, 2009. Liver transplantation (LT) is an effective treatment for patients with irreversible hepatic failure; however, mortality and morbidity are higher in critically ill recipients.1,2 Although hepatic encephalopathy (HE) is not included in the Model for End-Stage Liver Disease system of organ allocation, for patients with encephalopathy IV, there is no standard methodology for predicting whether a recipient will wake up from a deep coma after a technically successful transplant. Fulminant hepatic failure patients with an almost flat electroencephalogram have a chance of survival after LT, whereas some other patients do not recover consciousness.3 Brain edema and intracranial hypertension in acute liver failure have been emphasized for peritransplant monitor-

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“…There are also many laboratory solutions (prototypes) developed by different research groups, which were prepared and configured for a specific study. Monocular pupillometry systems have been previously proposed in [7,8]. Those systems used CCD linear sensors (90 Hz) and had relatively high precision parameters (0.05 and 0.01).…”

Section: Introductionmentioning

confidence: 99%

System and measurement method for binocular pupillometry to study pupil size variability

et al. 2014

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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.

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Measurement of pupil reactivity using fast pupillometry

Cited by 21 publications

References 44 publications

Photorealistic models for pupil light reflex and iridal pattern deformation

Photorealistic models for pupil light reflex and iridal pattern deformation

Clinical utility of an automated pupillometer for assessing and monitoring recipients of liver transplantation

System and measurement method for binocular pupillometry to study pupil size variability

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