scholarly journals A computational observer model of spatial contrast sensitivity: Effects of wavefront-based optics, cone mosaic structure, and inference engine

2018 ◽  
Author(s):  
Nicolas P. Cottaris ◽  
Haomiao Jiang ◽  
Xiaomao Ding ◽  
Brian A. Wandell ◽  
David H. Brainard
Keyword(s):  
Contrast Sensitivity ◽  
Human Performance ◽  
Inference Engine ◽  
Substantial Effect ◽  
Upper Bounds ◽  
Ideal Observer ◽  
Absolute Level ◽  
Spatial Frequencies ◽  
Spatial Contrast Sensitivity ◽  
Observer Model

We present a computational observer model of the human spatial contrast sensitivity (CSF) function based on the Image Systems EngineeringTools for Biology (ISETBio) simulation framework. We demonstrate that ISETBio-derived CSFs agree well with CSFs derived using traditional ideal observer approaches, when the mosaic, optics, and inference engine are matched. Further simulations extend earlier work by considering more realistic cone mosaics, more recent measurements of human physiological optics, and the effect of varying the inference engine used to link visual representations to psy-chohysical performance. Relative to earlier calculations, our simulations show that the spatial structure of realistic cone mosaics reduces upper bounds on performance at low spatial frequencies, whereas realistic optics derived from modern wavefront measurements lead to increased upper bounds high spatial frequencies. Finally, we demonstrate that the type of inference engine used has a substantial effect on the absolute level of predicted performance. Indeed, the performance gap between an ideal observer with exact knowledge of the relevant signals and human observers is greatly reduced when the inference engine has to learn aspects of the visual task. ISETBio-derived estimates of stimulus representations at different stages along the visual pathway provide a powerful tool for computing the limits of human performance.

scholarly journals A computational-observer model of spatial contrast sensitivity: Effects of wave-front-based optics, cone-mosaic structure, and inference engine

2019 ◽  
Vol 19 (4) ◽  
pp. 8 ◽  
Author(s):  
Nicolas P. Cottaris ◽  
Haomiao Jiang ◽  
Xiaomao Ding ◽  
Brian A. Wandell ◽  
David H. Brainard
Keyword(s):  
Wave Front ◽  
Contrast Sensitivity ◽  
Inference Engine ◽  
Mosaic Structure ◽  
Cone Mosaic ◽  
Spatial Contrast Sensitivity ◽  
Observer Model

Spatial Contrast Sensitivity of Migraine Patients Without Aura

Cephalalgia ◽  
2002 ◽  
Vol 22 (2) ◽  
pp. 142-145 ◽  
Author(s):  
K Benedek ◽  
J Tajti ◽  
M Janáky ◽  
L Vécsei ◽  
G Benedek
Keyword(s):  
Healthy Volunteers ◽  
Contrast Sensitivity ◽  
Migraine Without Aura ◽  
Marked Decrease ◽  
Primary Headache ◽  
Visual Pathway ◽  
Control Subjects ◽  
Spatial Frequencies ◽  
Spatial Contrast Sensitivity ◽  
Visual Disturbances

Visual disturbances are frequent symptoms in migraine. Since there is a possibility of separate damage in the magno- or parvo-cellular visual pathway in migraine patients, we performed a study including the measurement of static and dynamic spatial contrast sensitivity on 15 patients suffering from migraine without aura under photopic and scotopic conditions. Fifteen healthy volunteers without primary headache served as controls. The results revealed a marked decrease in contrast sensitivity at low spatial frequencies in the migraine patients. Spatial contrast sensitivity demonstrated some lateralization, as the sensitivity to low spatial frequencies obtained through separate eyes showed significantly larger side-differences in migraine patients than in control subjects. These findings suggest that the mechanisms responsible for vision at low spatial frequencies are impaired in migraine patients. This might indicate impaired function of the magnocellular pathways in this condition.

scholarly journals A computational observer model of spatial contrast sensitivity: Effects of photocurrent encoding, fixational eye movements and inference engine

2019 ◽  
Author(s):  
Nicolas P. Cottaris ◽  
Brian A. Wandell ◽  
Fred Rieke ◽  
David H. Brainard
Keyword(s):  
Eye Movements ◽  
Contrast Sensitivity ◽  
Cortical Neurons ◽  
Neural Population ◽  
Linear Filter ◽  
Response Dynamics ◽  
Translation Invariant ◽  
Fixational Eye Movements ◽  
Spatial Contrast Sensitivity ◽  
Observer Model

AbstractWe have recently shown that using the information carried by the mosaic of cone excitations of a stationary retina, the relative spatial contrast sensitivity function (CSF) of a computational observer has the same shape as a typical human subject. Absolute human sensitivity, however, is lower than the computational observer by a factor of 5 to 10. Here we model how additional known features of early vision affect spatial contrast sensitivity: fixational eye movements and the conversion of cone photopigment excitations to cone photocurrent responses. For a computational observer that uses a linear classifier applied to the responses of a stimulus-matched linear filter, fixational eye movements substantially change the shape of the spatial CSF, primarily by reducing sensitivity at spatial frequencies above 10 c/deg. For a computational observer that uses a translation-invariant calculation, in which decisions are based on the squared response of a quadrature-pair of linear filters, the CSF shape is little changed by eye movements, but there is a two-fold reduction in sensitivity. The noise and response dynamics of conversion of cone excitations into photocurrent introduce an additional two-fold sensitivity decrease. Hence, the combined effects of fixational eye movements and phototransduction bring the absolute sensitivity of the translation-invariant computational observer CSF to within a factor of 1 to 2 of the human CSF. We note that the human CSF depends on processing of the initial representation by many thalamic and cortical neurons, which are individually quite noisy. Our computational modeling suggests that the net effect of this noise on contrast-detection performance, when considered at the neural population level and behavioral level, is quite small: the inference mechanisms that determine the CSF, presumably in cortex, make efficient use of the information available from the cone photocurrents of the fixating eye.

scholarly journals Selectively reduced contrast sensitivity in high schizotypy

2019 ◽  
Vol 238 (1) ◽  
pp. 51-62
Author(s):  
Lauren Harper ◽  
Emily Spencer ◽  
Colin Davidson ◽  
Claire V. Hutchinson
Keyword(s):  
Contrast Sensitivity ◽  
Image Contrast ◽  
Life Questionnaire ◽  
First Report ◽  
Moving Stimuli ◽  
Spatial Frequencies ◽  
Spatial Contrast Sensitivity ◽  
Schizophrenic Patients

AbstractDeficits in the ability to encode small differences in contrast between adjacent parts of an image (contrast sensitivity) are well documented in schizophrenic patients. In the present study, we sought to determine whether contrast sensitivity deficits reported in schizophrenic patients are also evident in those who exhibit high schizotypy scores in a typical (i.e., non-schizophrenic) population. Using the O-Life Questionnaire, we determined the effects of schizotypy on spatial (0.5, 2 and 8 c/deg) and spatiotemporal (0.5 and 8 c/deg at 0.5 and 8 Hz) contrast sensitivity in 73 young (18–26 years), majority female (n = 68) participants. We found differences in contrast sensitivity that were spatial, spatiotemporal and O-Life subscale specific. Spatial contrast sensitivity was significantly lower in high, compared to low schizotypes at low spatial frequencies (0.5 c/deg) in those who scored highly on the Unusual Experiences and Cognitive Disorganisation O-Life subscales. For moving stimuli, individuals with high scores on the Unusual Experiences subscale exhibited lower spatiotemporal contrast sensitivity for 0.5 and 8 c/deg patterns drifting at 8 Hz. Although the effects reported here were relatively small, this is the first report of reduced contrast sensitivity in schizotypy.

scholarly journals Ideal observer analysis of the development of spatial contrast sensitivity in macaque monkeys

2003 ◽  
Vol 3 (10) ◽  
pp. 6 ◽  
Author(s):  
Lynne Kiorpes ◽  
Chao Tang ◽  
Michael J. Hawken ◽  
J. Anthony Movshon
Keyword(s):  
Contrast Sensitivity ◽  
Ideal Observer ◽  
Macaque Monkeys ◽  
Spatial Contrast Sensitivity ◽  
Ideal Observer Analysis

scholarly journals Lutein-Containing Antioxidants in Patients with Primary Open-Angle Glaucoma and Dry Type of Age-Related Macular Degeneration

2018 ◽  
Vol 15 (3) ◽  
pp. 339-347 ◽  
Author(s):  
D. A. Dorofeev
Keyword(s):  
Visual Acuity ◽  
Contrast Sensitivity ◽  
Primary Open Angle Glaucoma ◽  
Open Angle Glaucoma ◽  
Age Related Macular Degeneration ◽  
Control Group ◽  
Study Group ◽  
Age Related ◽  
Spatial Frequencies ◽  
Spatial Contrast Sensitivity

Objective.To assess the dynamics of structural-functional markers in patients with combined pathology: primary open-angle glaucoma (POAG) and age-related macular degeneration (AMD) with the background of lutein-containing drugs at long-term follow-up.Patients and Methods.The period of research was from November 2016 to January 2018; A parallel prospective study of patients (88 eyes), mean age 67.81 ± 8.41 (M ± σ); 67.64 (63.14; 73.08) (Me, Q25%, Q75%) years with combined pathology POAG and AMD (AREDS I and II). Patients were divided into 2 groups, the first group — a study group received Retinorm, by 1 capsule 3 times a day during a meal for 1 year, a second control group of 17 patients (32 eyes) did not receive lutein-containing medicines during the observation period. The study group consisted of 29 patients (55 eyes). There were 7 males and 22 females among them. The control group consisted of 19 patients (33 eyes), 2 males and 17 females among them. Visual acuity, standard automatic computer perimetry, optical coherence tomography, determination of spatial contrast sensitivity was carried out in all patients at the beginning of the study and after 1 year.Results.The maximum correlated visual acuity (MCVA) according to the table ETDRS increased in the study group and decreased in the control group, 95% the confidence interval for the changes in the MCVA: 0.1813636; 1.018182; 1.927273 и –3.878788; –2.393939; –0.8477273 (optotypes), respectively (W = 499.5; p = 0,0002919). Statistically significant changes in the thickness of the layer of nerve fibers of the retina (RNFL) neither in the middle nor in the sectors was revealed, and the thickness of the retina in oval foveal zone by sector: upper, temporal and lower statistically significantly decreased in the control group, while remaining unchanged in the observation group (р < 0.05). Spatial contrast sensitivity (SCS) after 1 year of use Retinorm remained at the same level in the control group, while there was a statistically significant increase in spatial contrast sensitivity in the main group, especially at high spatial frequencies is observed (р < 0.05).Conclusion.The results of the study indicate a positive effect of Retinorm used for 1 year. It was reflected in the improvement visual acuity in the distance, improvement of spatial contrast sensitivity, especially at high spatial frequencies, and the preservation of structural retinal indices both in the foveal zone and peripapillary.

Object Detection Using an Ideal Observer Model

2020 ◽  
Vol 2020 (16) ◽  
pp. 41-1-41-7
Author(s):  
Orit Skorka ◽  
Paul J. Kane
Keyword(s):  
Object Detection ◽  
Matched Filter ◽  
Image Sensors ◽  
Ideal Observer ◽  
Noise Power ◽  
Relative Evaluation ◽  
Detection And Identification ◽  
Cross Correlation Analysis ◽  
Observer Model ◽  
The Ideal

Many of the metrics developed for informational imaging are useful in automotive imaging, since many of the tasks – for example, object detection and identification – are similar. This work discusses sensor characterization parameters for the Ideal Observer SNR model, and elaborates on the noise power spectrum. It presents cross-correlation analysis results for matched-filter detection of a tribar pattern in sets of resolution target images that were captured with three image sensors over a range of illumination levels. Lastly, the work compares the crosscorrelation data to predictions made by the Ideal Observer Model and demonstrates good agreement between the two methods on relative evaluation of detection capabilities.

scholarly journals Aspheric Intraocular Lenses Implantation for Cataract Patients with Extreme Myopia

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Yanwen Fang ◽  
Yi Lu ◽  
Aizhu Miao ◽  
Yi Luo
Keyword(s):  
Contrast Sensitivity ◽  
Visual Quality ◽  
Intraocular Lenses ◽  
Wavefront Aberrations ◽  
Spatial Frequencies ◽  
Aspheric Iol ◽  
Significant Difference ◽  
Composite Scores ◽  
Cataract Patients

Objective. To evaluate the postoperative visual quality of cataract patients with extreme myopia after implantation of aspheric intraocular lenses (IOLs). Methods. Thirty-three eyes were enrolled in this prospectivestudy. Eighteen eyes with an axial length longer than 28 mm were included in the extreme myopia group, and the other 15 eyes were included in the nonextreme myopia group. Phacoemulsification and aspheric IOL implantation were performed. Six months after cataract surgery, best-corrected visual acuity (BCVA), contrast sensitivity, and wavefront aberrations were measured, and subjective visual quality was assessed. Results. The BCVA improved significantly after surgery for both groups, and patients in the nonextreme myopia group achieved better postoperative BCVA due to better retinal status of the eyes. The evaluation of contrast sensitivity without glare was the same in both groups, whereas patients in the nonextreme myopia group performed better at intermediate spatial frequencies under glare conditions. The two groups did not show a significant difference in high-order aberrations. With regard to subjective visual quality, the composite scores of both groups did not differ significantly. Conclusions. Aspheric IOLs provided good visual outcomes in cataract patients with extreme myopia. These patients should undergo careful evaluation to determine the maculopathy severity level before surgery.

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