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: Amblyopia and strabismus affect 2%-5% of the population and cause a broad range of visual deficits. The response to treatment is generally assessed using visual acuity, which is an insensitive measure of visual function and may, therefore, underestimate binocular vision gains in these patients. On the other hand, the contrast sensitivity function (CSF) generally takes longer to assess than visual acuity, but it is better correlated with improvement in a range of visual tasks and, notably, with improvements in binocular vision. The present study aims to assess monocular and binocular CSFs in amblyopia and strabismus patients. : Both monocular CSFs and the binocular CSF were assessed for subjects with amblyopia ( = 11), strabismus without amblyopia ( = 20), and normally sighted controls ( = 24) using a tablet-based implementation of the quick CSF, which can assess a full CSF in <3 min. Binocular summation was evaluated against a baseline model of simple probability summation. : The CSF of amblyopic eyes was impaired at mid-to-high spatial frequencies compared to fellow eyes, strabismic eyes without amblyopia, and control eyes. Binocular contrast summation exceeded probability summation in controls, but not in subjects with amblyopia (with or without strabismus) or strabismus without amblyopia who were able to fuse at the test distance. Binocular summation was less than probability summation in strabismic subjects who were unable to fuse. : We conclude that monocular and binocular contrast sensitivity deficits define important characteristics of amblyopia and strabismus that are not captured by visual acuity alone and can be measured efficiently using the quick CSF.

Despite the great evolution in the field of quality metrics, classical tools such as the PSNR remain useful in the field of evolution of video coding research. Our idea is to improve the limited performance of these tools using simple and well known techniques. In the quality measurement of images and video sequences, the use of the characteristics of human visual systems becomes a priority in order to have a better correlation between the objective measurement and the judgment of the observers. For this, we try to improve the performance of the two existing metrics (PSNR “Peak Signal / Noise Ratio”, DVQ “Digital Video Quality”) for the H.264 / MPEG-4 (Motion Picture Expert Group) AVC (Advanced Video Coding). This improvement is carried out by extracting the zones of interest using a saliency map and using a filtering by the contrast sensitivity function CSF. We did a study using two types of saliency map SURF (Speeded Up Robust Features) and HARRIS saliency map. We use the subjective video database “LIVE” to test the performance of our proposed idea. Performance indicators, namely Pearson (PLCC), the Spearman coefficient (SROCC) and mean squared prediction error (RMSE) indicate that SURF give best results for the distortion produced by H264 video encoding then HARRIS. Our idea is proven especially in short distances of observation.

The contrast sensitivity function that spans the two dimensions of contrast and spatial frequency is crucial in predicting functional vision both in research and clinical applications. In this study, the use of Bayesian inference was proposed to determine the parameters of the two-dimensional contrast sensitivity function. Two-dimensional Bayesian inference was extensively simulated in comparison to classical one-dimensional measures. Its performance on two-dimensional data gathered with different sampling algorithms was also investigated. The results showed that the two-dimensional Bayesian inference method significantly improved the accuracy and precision of the contrast sensitivity function, as compared to the more common one-dimensional estimates. In addition, applying two-dimensional Bayesian estimation to the final data set showed similar levels of reliability and efficiency across widely disparate and established sampling methods (from classical one-dimensional sampling, such as Ψ or staircase, to more novel multi-dimensional sampling methods, such as quick contrast sensitivity function and Fisher information gain). Furthermore, the improvements observed following the application of Bayesian inference were maintained even when the prior poorly matched the subject's contrast sensitivity function. Simulation results were confirmed in a psychophysical experiment. The results indicated that two-dimensional Bayesian inference of contrast sensitivity function data provides similar estimates across a wide range of sampling methods. The present study likely has implications for the measurement of contrast sensitivity function in various settings (including research and clinical settings) and would facilitate the comparison of existing data from previous studies.

With the widespread use of the Internet and the rapid development of digital technologies, copyright protection of multimedia content has become an important issue. Among the available technologies, digital watermarking techniques are regarded as a solution to the property right protection for multimedia resources. To evaluate the performance of a visible watermarking technique, robustness and perceptual translucence are two essential criteria for the watermark applications. In order to get the best trade-off between the embedding energy of a watermark and perceptual translucence, this study presents a technique named ICOCOA (innovated content and contrast aware) by exploiting the contrast sensitivity function (CSF) and noise reduction of human vision system in the wavelet domain. Another novel idea of this work is to propose the innovated CSF masking (I-CSF) curve which provides better weight perception where a game-theoretic architecture can be leveraged to determine the best I-CSF masking for the watermarked image. The experimental results demonstrate that the proposed approach not only provides a good translucent quality of the watermark but also achieves the robustness against the common image processing operations.

Purpose: A challenge in ocular preventive medicine is identification of patients with early pathological retinal damage that might benefit from nutritional intervention. The purpose of this study is to evaluate retinal thinning (RT) in early atrophic age-related macular degeneration (AMD) against visual function data from the Zeaxanthin and Visual Function (ZVF) randomized double masked placebo controlled clinical trial (FDA IND #78973). Methods: Retrospective, observational case series of medical center veterans with minimal visible AMD retinopathy (AREDS Report #18 simplified grading 1.4/4.0 bilateral retinopathy). Foveal and extra-foveal four quadrant SDOCT RT measurements were evaluated in n = 54 clinical and ZVF AMD patients. RT by age was determined and compared to the OptoVue SD OCT normative database. RT by quadrant in a subset of n = 29 ZVF patients was correlated with contrast sensitivity and parafoveal blue cone increment thresholds. Results: Foveal RT in AMD patients and non-AMD patients was preserved with age. Extrafoveal regions, however, showed significant slope differences between AMD patients and non-AMD patients, with the superior and nasal quadrants most vulnerable to retinal thinning (sup quad: −5.5 μm/decade thinning vs. Non-AMD: −1.1 μm/decade, P < 0.02; nasal quad: −5.0 μm/decade thinning vs. Non-AMD: −1.0 μm/decade, P < 0.04). Two measures of extrafoveal visual deterioration were correlated: A significant inverse correlation between % RT and contrast sensitivity (r = −0.33, P = 0.01, 2 Tailed Paired T) and an elevated extrafoveal increment blue cone threshold (r = +0.34, P = 0.01, 2 Tailed T). Additional SD OCT RT data for the non-AMD oldest age group (ages 82–91) is needed to fully substantiate the model. Conclusion: A simple new SD OCT clinical metric called “% extra-foveal RT” correlates well with functional visual loss in early AMD patients having minimal visible retinopathy. This metric can be used to follow the effect of repleting ocular nutrients, such as zinc, antioxidants, carotenoids, n-3 essential fats, resveratrol and vitamin D.

Perceptual Watermarking should take full advantage of the results from human visual system (HVS) studies. Just noticeable distortion (JND), which refers to the maximum distortion that the HVS does not perceive, gives a way to model the HVS accurately. An effective Spatio-Temporal JND model guided video watermarking scheme in DCT domain is proposed in this paper. The watermarking scheme is based on the design of an additional accurate JND visual model which incorporates spatial Contrast Sensitivity Function (CSF), temporal modulation factor, retinal velocity, luminance adaptation and contrast masking. The proposed watermarking scheme, where the JND model is fully used to determine scene-adaptive upper bounds on watermark insertion, allows providing the maximum strength transparent watermark. Experimental results confirm the improved performance of the Spatio-Temporal JND model. The authors’ Spatio-Temporal JND model is capable of yielding higher injected-watermark energy without introducing noticeable distortion to the original video sequences and outperforms the relevant existing visual models. Simulation results show that the proposed Spatio-Temporal JND model guided video watermarking scheme is more robust than other algorithms based on the relevant existing perceptual models while retaining the watermark transparency.

How much visual information about the retinal images can be extracted from the different layers of the visual pathway? This question depends on the complexity of the visual input, the set of transforms applied to this multivariate input, and the noise of the sensors in the considered layer. Separate subsystems (e.g. opponent channels, spatial filters, nonlinearities of the texture sensors) have been suggested to be organized for optimal information transmission. However, the efficiency of these different layers has not been measured when they operate together on colorimetrically calibrated natural images and using multivariate information-theoretic units over the joint spatio-chromatic array of responses. In this work, we present a statistical tool to address this question in an appropriate (multivariate) way. Specifically, we propose an empirical estimate of the information transmitted by the system based on a recent Gaussianization technique. The total correlation measured using the proposed estimator is consistent with predictions based on the analytical Jacobian of a standard spatio-chromatic model of the retina–cortex pathway. If the noise at certain representation is proportional to the dynamic range of the response, and one assumes sensors of equivalent noise level, then transmitted information shows the following trends: (1) progressively deeper representations are better in terms of the amount of captured information, (2) the transmitted information up to the cortical representation follows the probability of natural scenes over the chromatic and achromatic dimensions of the stimulus space, (3) the contribution of spatial transforms to capture visual information is substantially greater than the contribution of chromatic transforms, and (4) nonlinearities of the responses contribute substantially to the transmitted information but less than the linear transforms.

Our purpose is to develop and validate a new iPad-based contrast sensitivity (CS) test for measuring the contrast sensitivity function at near vision (Optopad-CSF). A total of 200 eyes of 100 healthy subjects (ages 17–63) were evaluated in a comparative study between the Optopad-CSF test (near vision) and the CSV-1000E test (distance vision). The agreement between tests was assessed with the index of contrast sensitivity (ICS) and the area under the curve (AUC). CS for all the spatial frequencies in both eyes showed a negative significant correlation with age, and corrected distance, and near visual acuities (r ≤ −0.512, p ≤ 0.013). A significantly lower CS was found with the Optopad-CSF test in the over-40-year-old subgroup for all the spatial frequencies evaluated compared to the below-40 subgroup (p ≤ 0.008). The mean AUC of the Optopad-CSF test (5.84) was twice that of the CSV-1000E test (2.76). The mean ICS of the Optopad-CSF (−0.019) and CSV-1000E (−0.075) tests showed similar values, both close to 0 (p = 0.3). There was a weak but significant correlation between the Optopad-CSF and CSV-1000E ICS tests (r = 0.246, p < 0.02). A range of normality for the values obtained with the Optopad-CSF test was calculated. The mean CS values in 16 bilateral cataract patients were out of the normal range for all the spatial frequencies evaluated (p < 0.001). Optopad-CSF is a valid portable system for measuring CS at near vision for five spatial frequencies, allowing the detection of age-related changes in CSF with age and CSF loss in cataracts, with no ceiling effect.

Routine assessments of the Contrast Sensitivity Function [CSF] could be useful for the diagnosis and monitoring of amblyopia. However, current CSF measures are not clinically practical, as they are too slow, too boring, and too uncomfortable to sustain a young child's interest. Here we assess the feasibility of a more gamified approach to CSF testing, in which a maximum likelihood psychophysical algorithm (QUEST+) is combined with a largely unconstrained user interface (no fixation target, head restraints, or discrete trials). Twenty-five amblyopes (strabismic, anisometropic, or mixed) aged 4.0–9.2 years performed the gamified CSF assessment monocularly (once per eye). The test required the child to “pop” (press) grating stimuli as they “bounced” around a tablet screen. Head tracking via the tablet's front-facing camera was used to adjust for variations in viewing distance post hoc . CSFs were fitted for each eye, and Area Under the CSF (AUCSF) computed as a summary measure of sensitivity. The results showed that AUCSF measurements were able to separate moderately and severely amblyopic eyes from fellow eyes (case-control effect), and to distinguish individuals with varying degrees of vision loss (dose effect). Even the youngest children exhibited no difficulties completing the test or comprehending what to do, and most children appeared to find the test genuinely enjoyable. Informal feedback from a focus group of older children was also positive, although potential shortcomings with the present design were identified. This feasibility study indicates that gamified, child-friendly vision assessments have promise as a future means of pediatric clinical assessment. Such measures could be particularly valuable for assessing children outside of conventional eye-care facilities (e.g., home-monitoring, school screening).

Relative scotopic spectral sensitivity depends only on the rhodopsin photopigment and ocular media absorption spectra. Rhodopsin is well characterised so the relative scotopic spectral sensitivity function can be calculated for intraocular lenses (IOLs) of known spectral density. In a recent perspective, Mainster and Sparrow concluded that an IOL with short wave absorbing chromophores would provide more retinal protection than conventional IOLs, but the practical consequences for scotopic vision are unclear. This paper uses published experiments to examine the implications for scotopic vision of the IOLs analysed by Mainster and Sparrow. A 14.6% reduction in scotopic sensitivity is expected for a SN60AT (AcrySof Natural) compared to a SA60AT (Conventional AcrySof) IOL under broadband illumination (equal quantum spectrum). This effect (0.07 log unit) is visually insignificant in relation to the ∼4.0 log unit range of scotopic sensitivity. More importantly, it is expected that scotopic contrast sensitivity would be reduced by only ∼0.01 log unit. It is thus improbable that a difference in scotopic vision between observers with the Natural and Conventional IOLs could be reliably detected using broadband stimuli.