scholarly journals The Effects of tDCS Across the Spatial Frequencies and Orientations that Comprise the Contrast Sensitivity Function

2015 ◽  
Vol 6 ◽  
Author(s):  
Bruno Richard ◽  
Aaron P. Johnson ◽  
Benjamin Thompson ◽  
Bruce C. Hansen
Keyword(s):  
Contrast Sensitivity ◽  
Sensitivity Function ◽  
Contrast Sensitivity Function ◽  
Spatial Frequencies

scholarly journals Photopic and Mesopic Contrast Sensitivity Function in the Presence of Glare and the Effect of Filters in Young Healthy Adults

2021 ◽  
Vol 12 ◽  
Author(s):  
Alberto Domínguez-Vicent ◽  
Emma Helghe ◽  
Marika Wahlberg Ramsay ◽  
Abinaya Priya Venkataraman
Keyword(s):  
Contrast Sensitivity ◽  
Light Transmission ◽  
Luminance Contrast ◽  
Sensitivity Function ◽  
Contrast Sensitivity Function ◽  
Selective Absorption ◽  
Light Reduction ◽  
Spatial Frequencies ◽  
Significant Difference ◽  
Young Subjects

Purpose: The aim of this study was to evaluate the effect of four different filters on contrast sensitivity under photopic and mesopic conditions with and without glare.Methods: A forced choice algorithm in a Bayesian psychophysical procedure was utilized to evaluate the spatial luminance contrast sensitivity. Five different spatial frequencies were evaluated: 1.5, 3, 6, 12, and 18 cycles per degree (cpd). The measurements were performed under 4 settings: photopic and mesopic luminance with glare and no glare. Two long pass filters (LED light reduction and 511nm filter) and two selective absorption filters (ML41 and emerald filter) and a no filter condition were evaluated. The measurements were performed in 9 young subjects with healthy eyes.Results: For the no filter condition, there was no difference between glare and no glare settings for the photopic contrast sensitivity measurements whereas in the mesopic setting, glare reduced the contrast sensitivity significantly at all spatial frequencies. There was no statistically significant difference between contrast sensitivity measurements obtained with different filters under both photopic conditions and the mesopic glare condition. In the mesopic no glare condition, the contrast sensitivity at 6 cpd with 511, ML41 and emerald filters was significantly reduced compared to no filter condition (p = 0.045, 0.045, and 0.071, respectively). Similarly, with these filters the area under the contrast sensitivity function in the mesopic no glare condition was also reduced. A significant positive correlation was seen between the filter light transmission and the average AULCSF in the mesopic non-glare condition.Conclusion: The contrast sensitivity measured with the filters was not significantly different than the no filter condition in photopic glare and no glare setting as well as in mesopic glare setting. In mesopic setting with no glare, filters reduced contrast sensitivity.

Masking Effects Induced by Perceptual Colour Components

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 85-85
Author(s):  
L Bedat ◽  
A Saadane ◽  
D Barba
Keyword(s):  
Contrast Sensitivity ◽  
Image Coding ◽  
Sine Wave ◽  
Sensitivity Function ◽  
Contrast Sensitivity Function ◽  
Masking Effect ◽  
Perception Threshold ◽  
Colour Image ◽  
Spatial Frequencies ◽  
Achromatic Contrast

Signals from the three types of cone photoreceptors are generally thought to be combined into two opponent-colour components and an achromatic component. Here we have chosen the cardinal directions Ach (achromatic axis), Cr1 (reddish - greenish axis) and Cr2 (bluish - yellowish axis) defined by Krauskopf to build a colour image coding scheme based on features of the human visual system. In order to design the optimal perceptual quantisers, we studied the perception of colour at different spatial frequencies, measuring the effect of a colour masking signal on the perception threshold for achromatic or chromatic sine-wave gratings. Three cases were considered to describe these interactions. First, we measured the masking effect of each colour component by itself. For the two chromatic components, we observed a pedestal effect for low masking contrasts and threshold rises for higher masking contrasts. Second, we studied interactions between the two colour axes. With colour masking signals composed of Cr1 and Cr2 components, thresholds for Cr1 stimuli dropped at low contrasts of the Cr2 component of the masking signal. This effect disappeared for high Cr2 masking contrasts. This was true at all contrasts of the Cr1 component of the masking signal. Thresholds for Cr2 stimuli were not modified by Cr1 masking. Finally, interactions between the chromatic and achromatic components were more complex. We observed a strong modification of the achromatic contrast-sensitivity function when a Cr1 masking sine-wave grating was added. When the achromatic frequency was lower than the colour masking frequency, the threshold rose. However, when the achromatic frequency was higher than the colour masking frequency, there was a significant pedestal effect. The global effect is a shift of the achromatic contrast sensitivity function. With a Cr2 masking signal, no significant modification of the achromatic contrast-sensitivity function was observed.

scholarly journals Contrast Sensitivity Function of the Albino Rat Determined Electrophysiologically

1998 ◽  
Vol 1 ◽  
pp. 11-17 ◽  
Author(s):  
Pilar Herreros de Tejada ◽  
Carmen Muñoz Tedó
Keyword(s):  
Visual Acuity ◽  
Contrast Sensitivity ◽  
Sensitivity Function ◽  
Contrast Sensitivity Function ◽  
Albino Rats ◽  
Lower Sensitivity ◽  
Experimental Conditions ◽  
Albino Rat ◽  
Spatial Frequencies ◽  
Luminance Threshold

Albinism alters the neural projections of the visual system. The authors wondered how this would affect visual function in rodents. They had previously shown that it doesn't alter the luminance threshold. They now explore visual acuity in the albino rat. In this work, they describe its contrast sensitivity function (CSF), as determined electro-physiologically. They recorded cortical visual evoked potentials (VEP) on six albino rats, stimulated by sinusoidal contrast reversal gratings. The curve showed the same characteristics that this function has in other mammals. Compared with the pigmented rat, the albino reached lower sensitivity values and showed a loss of sensitivity at high spatial frequencies. The estimated cut-off was 0.48 c/°, that is, 0.72 log units below the estimated cut-off for the pigmented rat under similar experimental conditions. VEP and behavioral cut-off were very close, the VEP estimation being slightly higher than the behavioral one.

scholarly journals Improvement in Contrast Sensitivity Function after Lacrimal Passage Intubation in Eyes with Epiphora

2020 ◽  
Vol 9 (9) ◽  
pp. 2761
Author(s):  
Sujin Hoshi ◽  
Kuniharu Tasaki ◽  
Takahiro Hiraoka ◽  
Tetsuro Oshika
Keyword(s):  
Contrast Sensitivity ◽  
Anterior Segment ◽  
Case Series ◽  
Sensitivity Function ◽  
Contrast Sensitivity Function ◽  
Corrected Visual Acuity ◽  
Spatial Frequencies ◽  
Before And After ◽  
Tear Meniscus ◽  
Prospective Case Series

This prospective case series aimed to investigate the contrast sensitivity function before and after lacrimal passage intubation (LPI) in eyes with epiphora due to lacrimal passage obstruction. We included 58 eyes of 51 patients who underwent LPI for lacrimal passage obstruction. The best-corrected visual acuity (BCVA), contrast sensitivity function, and lower tear meniscus were compared before LPI and one month after lacrimal duct stent removal. The area under the log contrast sensitivity function (AULCSF) was calculated for the analyses. Lower tear meniscus was assessed using anterior segment optical coherence tomography. The BCVA was comparable (p = 0.61) before and after LPI, while AULCSF increased significantly after treatment (before LPI: 1.29 ± 0.17, after LPI: 1.37 ± 0.14, p < 0.0001). Treatment resulted in a significant increase in contrast sensitivity at all spatial frequencies, 3–18 cycles/degree (p < 0.01 for 3, p < 0.01 for 6, p < 0.0005 for 12, p < 0.05 for 18 cycles/degree). The lower tear meniscus parameters improved significantly after treatment (p < 0.005); however, no correlation between the changes in the tear meniscus and those of the AULCSF was found. The contrast sensitivity significantly improved after LPI in eyes with epiphora due to lacrimal passage obstruction.

scholarly journals Contrast sensitivity before and after small incision lenticule extraction and femtosecond laser in situ keratomileusis

2019 ◽  
Vol 16 (4) ◽  
pp. 284-292
Author(s):  
Asik Pradhan ◽  
Kishore Raj Pradhan ◽  
Gauri Shankar Shrestha ◽  
Purushottam Dhunganga ◽  
Raju Kaiti
Keyword(s):  
Spatial Frequency ◽  
Contrast Sensitivity ◽  
Refractive Surgery ◽  
Sensitivity Function ◽  
Contrast Sensitivity Function ◽  
Laser In Situ Keratomileusis ◽  
Small Incision Lenticule Extraction ◽  
Spatial Frequencies ◽  
Lenticule Extraction

Introduction: Contrast sensitivity function after laser ablation of the cornea in refractive surgery is an important tool for measuring quality of visual function. The effect of small incision lenticule extraction (SMILE) and femtosecond laser in situ keratomileusis (FS-LASIK) on visual function can be compared by measuring spatial contrast sensitivity. Purpose: This study was to compare contrast sensitivity function in patients undergoing refractive surgery for myopia at Tilganga Institute of Ophthalmology. Methods: In a retrospective study, 15 subjects who underwent refractive surgeries comprising 9 cases of SMILE and 6 cases of FS-LASIK at Tilganga Eye Hospital were enrolled in the study. A major assessment included best corrected monocular contrast sensitivity with functional vision analyzer at spatial frequencies of 1.5, 3, 6, 12, and 18 cycles/deg in photopic condition (85 cd/m2) before, 3 months, and 1 year after the surgery. The average functional acuity contrast test scores for each spatial frequency were recorded. Differences between preoperative and postoperative contrast sensitivity at each spatial frequency were analyzed through parametric paired Student’s t-test. Results: Contrast sensitivity of postoperative FS-LASIK and SMILE did not differ from preoperative values at a photopic level. However, at high spatial frequency (12 and 18 cycles/deg), contrast sensitivity function improved significantly (p < 0.05) in eyes after FS-LASIK. Eyes after SMILE surgery did not show any reduction in contrast sensitivity at all the spatial frequencies. Conclusion: Under photopic conditions, the contrast sensitivity function is unaffected by SMILE or FS-LASIK.

Masking by Uniform Field Flicker: Some Practical Problems

Perception ◽  
1987 ◽  
Vol 16 (5) ◽  
pp. 641-647 ◽  
Author(s):  
David R Badcock ◽  
Elizabeth Sevdalis
Keyword(s):  
Visual System ◽  
Contrast Sensitivity ◽  
Human Visual System ◽  
Sensitivity Function ◽  
Relative Performance ◽  
Contrast Sensitivity Function ◽  
Uniform Field ◽  
Spatial Frequencies ◽  
The Mean ◽  
Mean Luminance

The technique of uniform field flicker (UFF) masking has frequently been used to address issues concerning the relative performance of sustained and transient neural channels in the human visual system. Unfortunately there has been an artifact in the implementation of this method in most published experiments which has meant that the contrast of the target has been flickered in synchrony with the mean luminance. A study is reported in which the artifact was corrected and the effects of UFF masking on the contrast sensitivity function then examined. With this correction, masking was still restricted to low spatial frequencies but it was much weaker than reported originally. It is argued that the original evidence suggesting that UFF masking can be used to examine the functioning of transient and sustained channels has not been interpreted correctly and that the basis for such a claim is weak.

Contrast Constancy Revisited: The Perceived Contrast of Sinusoidal Gratings above Threshold

2015 ◽  
Vol 68 (2) ◽  
pp. 363-380 ◽  
Author(s):  
Wayne S. Smith
Keyword(s):  
Visual System ◽  
Contrast Sensitivity ◽  
Local Adaptation ◽  
Significant Role ◽  
Stimulus Duration ◽  
Human Visual System ◽  
Sensitivity Function ◽  
Contrast Sensitivity Function ◽  
Spatial Frequencies ◽  
Sinusoidal Gratings

The contrast sensitivity function of the human visual system, measured with sinusoidal luminance gratings, has an inverted U shape with a peak around 2–4 c/deg. Above threshold, it is thought that luminance gratings of equal physical contrasts but of distinguishably different spatial frequencies are all perceived as having similar contrasts, a phenomenon that has been termed contrast constancy. However, when suprathreshold contrast matches were measured for pairs of luminance gratings whose spatial frequencies were indistinguishable, the matching curves were not flat and followed a similar inverted U shape form as the contrast sensitivity function at threshold. It was therefore suggested that contrast constancy may only be revealed when matching the contrasts of clearly distinguishable spatial frequencies. Here, observers matched the perceived contrasts of suprathreshold luminance gratings of similar but visibly different spatial frequencies between 0.25 and 16 c/deg. The results show that, much like the contrast sensitivity function at threshold, observers are more sensitive to intermediate spatial frequencies (1–6 c/deg) than they are to either higher or to lower spatial frequencies. This tuning is evident when matching reference contrasts of 30–80%, implying a significant role in everyday vision. To demonstrate that these results were not due to local adaptation, the experiment was repeated with shorter stimulus duration, producing the same results. The extent of departure from contrast constancy found in the present study is compared to previously reported suprathreshold measurements. The results are also discussed with consideration to limitations with display apparatus such as monitor blur.

scholarly journals Enhancing the contrast sensitivity function through action video game training

2009 ◽  
Vol 12 (5) ◽  
pp. 549-551 ◽  
Author(s):  
Renjie Li ◽  
Uri Polat ◽  
Walter Makous ◽  
Daphne Bavelier
Keyword(s):  
Contrast Sensitivity ◽  
Video Game ◽  
Sensitivity Function ◽  
Contrast Sensitivity Function ◽  
Action Video Game
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