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Silvestre Manzanera - One of the best experts on this subject based on the ideXlab platform.
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Adaptation to Brightness Perception in Patients Implanted With a Small Aperture.
American Journal of Ophthalmology, 2018Co-Authors: Silvestre Manzanera, Kyle Webb, Pablo ArtalAbstract:Purpose Small apertures are successfully used to extend depth of focus in presbyopic patients implemented either as corneal inlays or intraocular lenses. The use of small apertures reduces retinal illuminance. In this study, we quantify the relative Perceived Brightness in the 2 eyes of patients implanted monocularly with a small-aperture inlay. Design Prospective case series. Methods We used a binocular adaptive optics vision simulator to determine the relative Perceived Brightness. Four patients implanted monocularly with the KAMRA corneal inlay (1.6 mm) and a group of control subjects participated in the study. The projected pupil on the eye implanted with the inlay alternated in diameter between 0 and 2.5 mm (effective 1.6 mm) to eliminate potential for light to project around the periphery of the inlay while the corresponding fellow eye projected pupil alternated between 0 and 3.0 mm or 0 and 4.0 mm at a frequency of 1 Hz. Alternation on both eyes was synchronized so that only 1 eye at a time had a nonblocked pupil. At equal transmittance, a flickering was Perceived. Patients' task consisted of modifying the transmittance of the pupil corresponding to the fellow eye until the Perceived flickering, owing to the different Perceived Brightness, was minimized. This equalizing transmittance (ET) value indicates the relative Perceived Brightness. Results In the KAMRA's patients, ET was found to be greater than expected considering the difference in pupil sizes and the Stiles-Crawford effect, showing an enhanced a greater Brightness perception in the eye with the small aperture in comparison with the fellow eye. Compared with the control subjects, this difference was on average bigger by a factor of ×1.42. Conclusions Patients implanted with the small-aperture corneal inlay exhibited an enhanced Brightness perception with the eye implanted, in comparison with their untreated fellow eye. The amount of this increase is much larger than what could be expected owing to the Stiles-Crawford effect and was probably attributable to a neural adaptation process. This phenomenon could explain a reported equalization of Brightness between eyes in patients with unilateral inlays and implies that the expected reduction of Brightness may have a less significant impact on these patients, as expected.
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Perceived Brightness with small apertures
Journal of Cataract and Refractive Surgery, 2018Co-Authors: Pablo Artal, Silvestre ManzaneraAbstract:Purpose To quantify the relative Perceived Brightness when viewing through a small aperture as that used by presbyopic patients with small-aperture corneal inlays or intraocular lenses with an embedded aperture. Setting Laboratorio de Optica, Universidad de Murcia, Murcia, Spain. Design Prospective case series. Methods The relative Perceived Brightness when 2 apertures (3.0 mm and 1.6 mm diameters) were presented monocularly to the participant was determined. With equal transmittances in both apertures, a flickering effect caused by the different retinal illuminance for each condition is Perceived. The participant's task was to modify the transmittance of the 3.0 mm pupil until the flickering was minimized. This transmittance value indicates the relative Perceived Brightness reduction. The measurements were performed under 3 average luminance levels. Results The Perceived relative luminance measured ranged between 38.5% and 46.9%. This represents an increase in Brightness perception with a small aperture of 1.24 and 1.51, respectively, compared with what would be expected. This trend was consistent for all the participants in the study. Conclusions The Perceived Brightness with a small aperture was less pronounced than what would be predicted by the reduction in retinal illuminance. Under real visual conditions, this effect could be even more significant because binocular effects and temporal adaptation might further increase the Perceived Brightness with the small aperture.
Pablo Artal - One of the best experts on this subject based on the ideXlab platform.
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Adaptation to Brightness Perception in Patients Implanted With a Small Aperture.
American Journal of Ophthalmology, 2018Co-Authors: Silvestre Manzanera, Kyle Webb, Pablo ArtalAbstract:Purpose Small apertures are successfully used to extend depth of focus in presbyopic patients implemented either as corneal inlays or intraocular lenses. The use of small apertures reduces retinal illuminance. In this study, we quantify the relative Perceived Brightness in the 2 eyes of patients implanted monocularly with a small-aperture inlay. Design Prospective case series. Methods We used a binocular adaptive optics vision simulator to determine the relative Perceived Brightness. Four patients implanted monocularly with the KAMRA corneal inlay (1.6 mm) and a group of control subjects participated in the study. The projected pupil on the eye implanted with the inlay alternated in diameter between 0 and 2.5 mm (effective 1.6 mm) to eliminate potential for light to project around the periphery of the inlay while the corresponding fellow eye projected pupil alternated between 0 and 3.0 mm or 0 and 4.0 mm at a frequency of 1 Hz. Alternation on both eyes was synchronized so that only 1 eye at a time had a nonblocked pupil. At equal transmittance, a flickering was Perceived. Patients' task consisted of modifying the transmittance of the pupil corresponding to the fellow eye until the Perceived flickering, owing to the different Perceived Brightness, was minimized. This equalizing transmittance (ET) value indicates the relative Perceived Brightness. Results In the KAMRA's patients, ET was found to be greater than expected considering the difference in pupil sizes and the Stiles-Crawford effect, showing an enhanced a greater Brightness perception in the eye with the small aperture in comparison with the fellow eye. Compared with the control subjects, this difference was on average bigger by a factor of ×1.42. Conclusions Patients implanted with the small-aperture corneal inlay exhibited an enhanced Brightness perception with the eye implanted, in comparison with their untreated fellow eye. The amount of this increase is much larger than what could be expected owing to the Stiles-Crawford effect and was probably attributable to a neural adaptation process. This phenomenon could explain a reported equalization of Brightness between eyes in patients with unilateral inlays and implies that the expected reduction of Brightness may have a less significant impact on these patients, as expected.
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Perceived Brightness with small apertures
Journal of Cataract and Refractive Surgery, 2018Co-Authors: Pablo Artal, Silvestre ManzaneraAbstract:Purpose To quantify the relative Perceived Brightness when viewing through a small aperture as that used by presbyopic patients with small-aperture corneal inlays or intraocular lenses with an embedded aperture. Setting Laboratorio de Optica, Universidad de Murcia, Murcia, Spain. Design Prospective case series. Methods The relative Perceived Brightness when 2 apertures (3.0 mm and 1.6 mm diameters) were presented monocularly to the participant was determined. With equal transmittances in both apertures, a flickering effect caused by the different retinal illuminance for each condition is Perceived. The participant's task was to modify the transmittance of the 3.0 mm pupil until the flickering was minimized. This transmittance value indicates the relative Perceived Brightness reduction. The measurements were performed under 3 average luminance levels. Results The Perceived relative luminance measured ranged between 38.5% and 46.9%. This represents an increase in Brightness perception with a small aperture of 1.24 and 1.51, respectively, compared with what would be expected. This trend was consistent for all the participants in the study. Conclusions The Perceived Brightness with a small aperture was less pronounced than what would be predicted by the reduction in retinal illuminance. Under real visual conditions, this effect could be even more significant because binocular effects and temporal adaptation might further increase the Perceived Brightness with the small aperture.
Naoyuki Osaka - One of the best experts on this subject based on the ideXlab platform.
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primary visual cortex scales individual s Perceived Brightness with power function inner psychophysics with fmri
Journal of Experimental Psychology: Human Perception and Performance, 2012Co-Authors: Hiroyuki Tsubomi, Takashi Ikeda, Naoyuki OsakaAbstract:: Perceived Brightness is well described by Stevens' power function (S. S. Stevens, 1957, On the psychophysical law, Psychological Review, Vol. 64, pp. 153-181), with a power exponent of .33 (the cubic-root function of luminance). The power exponent actually varies across individuals, yet little is known about neural substrates underlying this individual difference. The present functional MRI study investigated how neural activation levels in the visual cortex serve to scale individual's subjective Brightness. Participants rated Brightness of a disk ranging from 1- to 100-cd/m² luminance. Subjective Brightness ratings showed an almost perfect log-linear dependence on luminance intensity, with the power exponent averaging .32. The fMRI results showed that activity in the bilateral primary visual cortex along with the calcarine sulcus (also known as Brodmann's area 17 and V1) increased log-linearly with physical luminance, showing average power exponents of .32 and .27 in the left and right hemispheres, respectively. There were substantial individual variations in the power function exponents for both subjective Brightness ratings (.14 to .46) and primary visual cortex activation (.12 to .55). An important finding was that 2 power exponents were closely correlated (r = .62). Subjective Brightness ratings and primary visual cortex activation were both better correlated with stimulus luminance than stimulus contrast (at the border of the stimulus). These results suggest that primary visual cortex activation can scale individual's subjective Brightness in accordance with Stevens' power law.
Ulrich Eisemann - One of the best experts on this subject based on the ideXlab platform.
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refinement of a model for predicting Perceived Brightness
electronic imaging, 2001Co-Authors: Ulrich EisemannAbstract:In this paper, an updated version of a previously proposed model for the prediction of Perceived Brightness is presented. The model is not only applicable to simple spatial configurations but also to complex scenes and relies entirely on physical and colorimetric data. These are derived from a complex description of the entire scene which eliminates the need for a priori knowledge like the popular reference white concept and others. The model includes an extensive preprocessing stage consisting of a central projection to transform the scene description into a pixel-oriented image, a simple pixel classification to identify the stimulus region and extensive histogram calculations to extract quantiles as characteristic features. Based on the quantiles, which form the output of the preprocessing stage and represent the distribution of luminance levels within the scene, a map has been implemented to calculate a value characterizing the Perceived Brightness. The development of the model structure was inspired by a series of haploscopic Brightness matching experiments, whose experimental data were also used to train and test the model. The results are quite encouraging because the differences between experimental and model-predicted Brightness values rarely exceed the range of the natural inter-observer deviations.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
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Color Imaging: Device-Independent Color, Color Hardcopy, and Applications - Refinement of a model for predicting Perceived Brightness
electronic imaging, 2001Co-Authors: Ulrich EisemannAbstract:In this paper, an updated version of a previously proposed model for the prediction of Perceived Brightness is presented. The model is not only applicable to simple spatial configurations but also to complex scenes and relies entirely on physical and colorimetric data. These are derived from a complex description of the entire scene which eliminates the need for a priori knowledge like the popular reference white concept and others. The model includes an extensive preprocessing stage consisting of a central projection to transform the scene description into a pixel-oriented image, a simple pixel classification to identify the stimulus region and extensive histogram calculations to extract quantiles as characteristic features. Based on the quantiles, which form the output of the preprocessing stage and represent the distribution of luminance levels within the scene, a map has been implemented to calculate a value characterizing the Perceived Brightness. The development of the model structure was inspired by a series of haploscopic Brightness matching experiments, whose experimental data were also used to train and test the model. The results are quite encouraging because the differences between experimental and model-predicted Brightness values rarely exceed the range of the natural inter-observer deviations.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
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influence of spatial luminance interactions on Perceived Brightness
Proceedings of SPIE, 2000Co-Authors: Ulrich EisemannAbstract:Most color appearance models that have been published so far require a simplified description of the viewing field which is subdivided into a small number of homogeneous regions. The tristimulus values and luminance levels of these regions serve as input parameters for the models. The purpose of this paper however is to study Brightness perception in a complex, achromatic surround using a more detailed description of the entire viewing field. Therefore, a number of psycho physical experiments were carried out using a CRT display on which relatively complex images were presented. Several observers were asked to judge the Perceived Brightness by adjusting the luminance level of a reference grey for a perfect Brightness match. All thereby obtained psycho physical data were used to develop a new Brightness appearance model that takes all objects in the entire visual field into account. The model includes an object feature extraction stage, in which object properties like area and position are extracted, a stage in which the characteristic object data are sorted into the appropriate classes of a histogram and a multivariate map in the form of a feedforward neural network to calculate the prediction of the Perceived Brightness.
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Color Imaging: Device-Independent Color, Color Hardcopy, and Graphic Arts - Influence of spatial luminance interactions on Perceived Brightness
Proceedings of SPIE, 2000Co-Authors: Ulrich EisemannAbstract:Most color appearance models that have been published so far require a simplified description of the viewing field which is subdivided into a small number of homogeneous regions. The tristimulus values and luminance levels of these regions serve as input parameters for the models. The purpose of this paper however is to study Brightness perception in a complex, achromatic surround using a more detailed description of the entire viewing field. Therefore, a number of psycho physical experiments were carried out using a CRT display on which relatively complex images were presented. Several observers were asked to judge the Perceived Brightness by adjusting the luminance level of a reference grey for a perfect Brightness match. All thereby obtained psycho physical data were used to develop a new Brightness appearance model that takes all objects in the entire visual field into account. The model includes an object feature extraction stage, in which object properties like area and position are extracted, a stage in which the characteristic object data are sorted into the appropriate classes of a histogram and a multivariate map in the form of a feedforward neural network to calculate the prediction of the Perceived Brightness.
Jussi Saarinen - One of the best experts on this subject based on the ideXlab platform.
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visual features underlying Perceived Brightness as revealed by classification images
PLOS ONE, 2009Co-Authors: Ilmari Kurki, Tarja Peromaa, Aapo Hyvarinen, Jussi SaarinenAbstract:Along with physical luminance, the Perceived Brightness is known to depend on the spatial structure of the stimulus. Often it is assumed that neural computation of the Brightness is based on the analysis of luminance borders of the stimulus. However, this has not been tested directly. We introduce a new variant of the psychophysical reverse-correlation or classification image method to estimate and localize the physical features of the stimuli which correlate with the Perceived Brightness, using a Brightness-matching task. We derive classification images for the illusory Craik-O'Brien-Cornsweet stimulus and a “real” uniform step stimulus. For both stimuli, classification images reveal a positive peak at the stimulus border, along with a negative peak at the background, but are flat at the center of the stimulus, suggesting that Brightness is determined solely by the border information. Features in the perceptually completed area in the Craik-O'Brien-Cornsweet do not contribute to its Brightness, nor could we see low-frequency boosting, which has been offered as an explanation for the illusion. Tuning of the classification image profiles changes remarkably little with stimulus size. This supports the idea that only certain spatial scales are used for computing the Brightness of a surface.