Contrast Sensitivity Function Research Articles

Reduced contrast sensitivity function and outer retina thickness in convalescent Vogt-Koyanagi-Harada disease.

To evaluate contrast sensitivity function (CSF) in convalescent Vogt-Koyanagi-Harada (VKH) disease and investigate the relationship between CSF and chorioretinal thickness in VKH patients with and without sunset glow fundus (SGF). This is a cross-sectional study. Seventy-six eyes of VKH patients and 56 eyes of normal controls were evaluated. Patients were divided into SGF and non-SGF groups. The best-corrected visual acuity (BCVA) of all the participants was ≤0.0 logMAR. Their CSF and macular chorioretinal thickness were measured with quantitative CSF (qCSF) and Optical Coherence Tomography (OCT) and compared using repeated measures analysis of variance at the group level. Relationships between CSF and macular chorioretinal thickness were evaluated using generalized estimating equations. The CSF was significantly impaired in the SGF group compared to that in the control group (p = 0.001), especially at medium and high spatial frequencies. No significant CSF difference was found between the non-SGF group and control group, nor between the SGF and non-SGF groups. Compared to the controls, outer retinal thickness (ORT) in both VKH subgroups was significantly reduced (P < 0.001 or 0.005, respectively), although their outer nuclear layer thickness (ONLT) and choroidal thickness (CT) were not significantly different (both P = 1.000, P = 0.829 or 0.112, respectively). We found no significant correlation between CSF metrics and outer retinal thickness. Despite good recovery of visual acuity, reduced CSF and outer retina thickness were found in convalescent VKH patients. CSF may be an important and sensitive metric to evaluate functional vision in VKH disease.

How the window of visibility varies around polar angle.

Contrast sensitivity, the amount of contrast required to discriminate an object, depends on spatial frequency (SF). The contrast sensitivity function (CSF) peaks at intermediate SFs and drops at other SFs. The CSF varies from foveal to peripheral vision, but only a couple of studies have assessed how the CSF changes with polar angle of the visual field. For many visual dimensions, sensitivity is better along the horizontal than the vertical meridian and at the lower than the upper vertical meridian, yielding polar angle asymmetries. Here, for the first time, to our knowledge, we investigate CSF attributes around polar angle at both group and individual levels and examine the relations in CSFs across locations and individual observers. To do so, we used hierarchical Bayesian modeling, which enables precise estimation of CSF parameters. At the group level, maximum contrast sensitivity and the SF at which the sensitivity peaks are higher at the horizontal than vertical meridian and at the lower than the upper vertical meridian. By analyzing the covariance across observers (n = 28), we found that, at the individual level, CSF attributes (e.g., maximum sensitivity) across locations are highly correlated. This correlation indicates that, although the CSFs differ across locations, the CSF at one location is predictive of that at another location. Within each location, the CSF attributes covary, indicating that CSFs across individuals vary in a consistent manner (e.g., as maximum sensitivity increases, so does the corresponding SF), but more so at the horizontal than the vertical meridian locations. These results show similarities and uncover some critical polar angle differences across locations and individuals, suggesting that the CSF should not be generalized across isoeccentric locations around the visual field.

Exploring the Impact of Blood Draws on the Intraocular Pressure of Older Adults: A Focus on Physiological Responses.

Background/Objectives: This study investigated intraocular pressure (IOP) changes after a blood draw in older adults considering sex, age, and baseline IOP. Methods: Fifty-three subjects (54.7% females; age: 68.50 ± 4.46 years; Visual Function Index [VF14]: 94.50 ± 7.50 points; mean contrast sensitivity function (CSF) for both eyes in each spatial frequency [cdp]: 1.5 cdp [1.41 ± 0.20 log], 3 cdp [1.57 ± 0.29 log], 6 cdp [1.45 ± 0.39 log], 12 cdp [1.04 ± 0.40 log], 18 cdp [0.63 ± 0.31 log]) voluntarily participated. Subjects fasted for at least 8 h before attending the laboratory. First, IOP was measured in a seated position using a portable rebound tonometer. Ten minutes after the initial measurement, two 10 mL tubes of blood were drawn. Five minutes after the blood draw IOP was measured again following the same procedure as the initial measurement. We evaluated the differences using an analysis of variance. Results: Significant, but not clinically relevant, decreases were found in the right eye, with small effect sizes (p = 0.013-0.079, d = 0.35). Only males and subjects older than 68 years showed trends toward IOP reduction in the right eye. Subjects with baseline IOP ≥ 14 mmHg experienced significant IOP reductions in both eyes, with moderate effect sizes (p = 0.001-0.002, d = 0.56-0.69). Conclusions: Our findings suggest that a blood draw of 20 mL is safe for the IOP levels of older adults with baseline IOP between 11 and 21 mmHg. Variations in IOP were observed based on baseline IOP, sex, and age, suggesting the importance of personalized clinical assessments. The primary factor influencing IOP changes appears to be the baseline IOP level.

Quantifying the Functional Relationship Between Visual Acuity and Contrast Sensitivity Function.

Studies have reported that individuals with certain ocular disorders may have significant decreases in contrast sensitivity function (CSF) despite having normal or near normal visual acuity (VA). This study seeks to elucidate this phenomenon by investigating the relationship between VA and CSF. We analyzed data from 14 eyes tested with Electronic Early Treatment Diabetic Retinopathy and quantitative CSF under four Bangerter foil conditions (n = 56). From the CSF data, we estimated peak gain, peak frequency, and contrast sensitivity acuity (CSA). We explored the correlations between VA and various CSF parameters and evaluated five predictive models of VA using CSA alone and in combination with additional CSF parameters through ridge regression. We found that similar VA scores can correspond with markedly different CSFs and observed significant correlations among all CSF parameters and between VA and each CSF parameter (all P < 0.001). The most effective predictive model, incorporating CSA and peak gain, explained 90.97% of the variance with a root mean squared error of 0.0676 logMAR, which is comparable with the average standard deviation of the VA scores (0.0627 logMAR) and accounted for 38.6% of the residual variance not explained by the CSA-alone model. This study offers the first empirical inference of the quantitative relationship between VA and CSF, suggesting that various CSF parameter combinations can yield identical VA. This might help to explain why some clinical populations with normal or near-normal VA exhibit significant CSF deficits and calls for further research in different clinical settings.

Impact of Keratoconus on Contrast Sensitivity

Objective: Keratoconus (KC) disrupts corneal shape, leading to irregular astigmatism and increased higher-order aberrations (HOA), ultimately affecting visual quality. While visual acuity (VA) remains the standard, its limitations in early KC diagnosis are recognized. This study aimed to evaluate the impact of KC on contrast sensitivity function (CSF), a potentially more sensitive measure of visual performance.Material and Methods: A case-control design compared CSF in KC patients (n=7) to healthy controls (n=16). All subjects achieved the best-corrected visual acuity (BCVA) of 6/9 or better (logMAR ≤0.10). Corneal topography was measured using Tomey TMS-5 to confirm KC diagnosis. CSF was assessed with the Functional Acuity Contrast Test (FACT).Results: KC eyes exhibited significantly reduced CSF across all spatial frequencies compared to controls (p-value&lt;0.05). Row A of the FACT chart (representing the lowest spatial frequency, 1.5 cpd) demonstrated the most prominent difference (t (21)=-3.073, p-value=0.003).Conclusion: Our findings reveal that KC patients, despite achieving good BCVA, demonstrate measurable deficits in CSF. This suggests CSF measurement with FACT may be a valuable tool for the early diagnosis and monitoring of KC, potentially offering a more sensitive and comprehensive assessment of visual function compared to BCVA alone.

Understanding contrast perception in amblyopia: a psychophysical analysis of the ON and OFF visual pathways.

The study aimed to explore potential discrepancies in contrast sensitivity in the ON and OFF visual pathways among individuals with amblyopia compared to controls. Eleven adult amblyopes (26.2 ± 4.4 [SD] years old) and 10 controls (24.6 ± 0.8 years old) with normal or corrected to normal visual acuity (logMAR VA ≤ 0) participated in this study. Using the quick contrast sensitivity function (qCSF) algorithm, we measured balanced CSF which would stimulate the ON and OFF pathways unselectively, and CSFs for increments and decrements that would selectively stimulate the ON and OFF visual pathways. Contrast sensitivity and area under log contrast sensitivity function were extracted for statistical analysis. For the balanced CSF, we found significant interocular differences in sensitivity and area under log contrast sensitivity function in both amblyopes [F(1,10) = 74.992, p < 0.001] and controls [F(1,9) = 35.6, p < 0.001], while such differences were more pronounced in amblyopes than in controls. For increment and decrement CSFs, we found that the increment sensitivity (p = 0.038) and area under log contrast sensitivity function (p = 0.001) were significantly lower than the decrement in the amblyopic eye. Such differences between increment and decrement CSFs were not observed in the fellow eye of the amblyopes or in the controls. There is a subtle difference in the contrast sensitivity of the amblyopic eye when exposed to stimulation in the ON and OFF pathways.

Comparison of the quantitative contrast sensitivity function between early keratoconus and normal eyes

PurposeTo compare the characteristics of the quantitative contrast sensitivity function (qCSF) in eyes with early keratoconus (Early-KC) and normal control (NC) eyes and investigate the associated factors.DesignA cross-sectional study.MethodsThis study included 43 eyes of 43 patients with Early-KC (including subclinical keratoconus [SKC] and forme fruste keratoconus [FFKC]) and 77 NC eyes of 77 participants with corrected distance visual acuity (CDVA) all ≥ 20/20. Contrast sensitivity (CS) was assessed using the qCSF tests. Subgroup analysis was performed according to keratoconus type(SKC and FFKC) and astigmatism(cylindrical refraction >-1.0D or ≤-1.0D).ResultsSex ratio, spherical refraction, and spherical equivalent (SE) varied significantly between the two groups (all P < 0.01). The area under log CSF (AULCSF), CSF Acuity, and CS at low (1.0 and 1.5 cycles per degree [cpd]) and high (12.0 and 18.0 cpd) spatial frequencies decreased significantly in the Early-KC group than that in the NC group (all P < 0.05). The subgroup analysis revealed a similar decrease in the SKC group (all P < 0.05). AULCSF, CSF Acuity, and CS at high spatial frequencies of patients with cylindrical refraction ≤-1.0D in the Early-KC group decreased significantly (all P < 0.05) than those in the NC group. The index of vertical asymmetry and index of height decentration correlated negatively with CS at 1.5 cpd (r= -0.321 and -0.306; both P < 0.05).ConclusionsCS decreased significantly at low and high spatial frequencies in Early-KC, though with normal CDVA. The qCSF test can sensitively reflect visual performance in early keratoconus.

Predicting contrast sensitivity functions with digital twins

We developed and validated digital twins (DTs) for contrast sensitivity function (CSF) across 12 prediction tasks using a data-driven, generative model approach based on a hierarchical Bayesian model (HBM). For each prediction task, we utilized the HBM to compute the joint distribution of CSF hyperparameters and parameters at the population, subject, and test levels. This computation was based on a combination of historical data (N = 56), any new data from additional subjects (N = 56), and “missing data” from unmeasured conditions. The posterior distributions of the parameters in the unmeasured conditions were used as input for the CSF generative model to generate predicted CSFs. In addition to their accuracy and precision, these predictions were evaluated for their potential as informative priors that enable generation of synthetic quantitative contrast sensitivity function (qCSF) data or rescore existing qCSF data. The DTs demonstrated high accuracy in group level predictions across all tasks and maintained accuracy at the individual subject level when new data were available, with accuracy comparable to and precision lower than the observed data. DT predictions could reduce the data collection burden by more than 50% in qCSF testing when using 25 trials. Although further research is necessary, this study demonstrates the potential of DTs in vision assessment. Predictions from DTs could improve the accuracy, precision, and efficiency of vision assessment and enable personalized medicine, offering more efficient and effective patient care solutions.

Crocus sativus (saffron) and age-related macular degeneration.

Age-related macular degeneration (ARMD) leads to impaired vision and potential blindness. Globally, it accounts for approximately 9% of vision loss cases, and a projected 288 million individuals will be affected by 2040. Current treatments have limitations such as variable effectiveness, high costs, and potential side effects. Additionally, atrophic ARMD management remains challenging. As saffron has shown promising neuroprotective and antioxidant effects by potentially delaying disease progression, this study aims to review the mechanistic, pre-clinical, and clinical evidence of the effects, safety, and tolerability of saffron in ARMD treatment. The Scale for the Assessment of Narrative Review Articles was applied in this narrative review. To find relevant literature, the syntax "(saffron OR crocus) AND (retin* OR "geographic atrophy" OR "choroidal neovascular*" OR "macular degeneration")" was searched in PubMed/MEDLINE. Pre-clinical and clinical original investigations of the effects of saffron in ARMD along with the eligible studies cited in their reference lists were identified and included. Saffron and its active compounds, crocin and crocetin, have shown promising results in improving visual function and delaying ARMD progression. Several clinical studies have found that daily supplementation with 20-50 mg of saffron or 5-15 mg of crocin for 3-12 months significantly improved best-corrected visual acuity, contrast sensitivity, and retinal function as measured by electroretinogram and microperimetry, with benefits observed in both dry and wet forms of ARMD. The effects were independent of genetic risk factors and maintained during the follow-up periods, suggesting the potential role of saffron as a long-term treatment option. Saffron reduces ARMD progression via anti-angiogenic, neuroprotective, and antioxidant mechanisms. Moreover, saffron is safe and well tolerated. Although further research is needed to confirm long-term safety and efficacy, current evidence supports the use of saffron or crocin supplements as a safe and tolerable adjunct therapy for ARMD management.

Chondroitin sulfate in invertebrate development

AbstractChondroitin sulfate (CS) is one of the most evolutionarily conserved glycosaminoglycans (GAGs). Although CS's function in skeletal development is well established in vertebrates, CS exists in more primitive animal species with no cartilage or bone, such as C. elegans and Drosophila, indicating that the original role of CS was not in the skeletal system. In this review, we focus on the roles of CS and the mechanisms of action during development of two genetically trackable model organisms, C. elegans and Drosophila.

Visual Performance of People With Albinism Assessed With Generalizable and Adaptive AIM and FInD Methods.

People with albinism (PwA) are known to have visual impairments; however, little is known about whether these functions are disrupted across earlier and later stages of the visual pathway. We investigated distinct perceptual functions and fixation stability within each observer and compared the data with age- (±5years) and sex-matched controls. Twenty-one self-reported PwA and twenty-one controls were recruited. Angular-indication measurement (AIM) and foraging-interactive-D-prime (FInD) psychophysical methods were deployed to measure OS, OD, and OU near visual acuity, spatial contrast sensitivity function (CSF), temporal contrast sensitivity (tCS; 0.5 c/°; horizontal grating: 0, 1, 2, 4, and 8Hz), OU glare acuity, threshold-versus-contrast (2c/° vertical grating), long, medium, and short wavelength cone-isolated color detection, color discrimination, stereoacuity across spatial frequencies (1c/°, 2c/°, 4c/°, 8c/°), horizontal, circular, radial pattern and motion coherence, and equivalent-noise motion detection. Thresholds were determined by AIM and FInD and compared using N-ANOVAs, t-tests, planned multi-comparisons, correlations, and unsupervised, agglomerative hierarchical cluster analysis for each group. We found significant differences between groups for most visual functions except for simple and complex form-coherence (two way-ANOVAs, P > 0.05) and complex motion coherence. Correlations between outcomes revealed more significant correlations for PwA and differences in the specific correlates between groups. Unsupervised hierarchical clustering revealed different functional clusters between groups. AIM and FInD successfully interrogated visual deficits in PwA. Overall, PwA showed impaired performance in achromatic, chromatic, temporal, and binocular functions, and had higher intrinsic noise levels. Midlevel vision was comparable between groups. Unsupervised cluster analysis and correlation between outcomes revealed a difference in functional outcome clusters between groups. The results may help to increase the efficiency of screening and identify target deficits for rehabilitation.

Visual Performance of School-age Children Wearing Dual-Focus Soft Contact Lenses: A Randomized Controlled Trial

To investigate the effect of wearing dual-focus soft contact lenses (DFSCL) on the visual performance of school-age children. In this randomized controlled clinical trial, 64 children aged 8 to 12 years with spherical equivalent refraction between -0.75 D and -4.00 D were recruited in our hospital in October 2022. Using the envelope method, the subjects were evenly and randomly assigned to the control group wearing single vision spectacles (SVS) or the intervention group wearing MiSight dual-focus soft contact lenses (DFSCL) from CooperVision. Follow-up examinations were conducted once every 3 months. The corrected visual acuity, contrast sensitivity function (CSF), and the scores for National Eye Institute Refractive Error Quality of Life Instrument-42 (NEI-RQL-42) were compared between the control and intervention groups. By December 2023, a total of 58 subjects completed follow-up (30 in the SVS group and 28 in the DFSCL group). No significant difference in corrected visual acuity was observed between subjects wearing DFSCL and those wearing SVS. The CSF of the DFSCL group was comparable to that of the SVS group across the spatial frequencies of 3, 6, 12, and 18 cpd (P>0.05). According to the results of the NEI-RQL-42 survey at the 6-month follow-up, the score for ocular discomfort symptoms was 89±14 in the SVS group and 79±16 in the DFSCL group (P=0.008), reflecting that the DFSCL group had a 12.66% higher level of discomfort. For appearance, the score was 70±32 in the SVS group and 92±22 in the DFSCL group (P=0.002), showing a 31.43% improvement in the DFSCL group. In addition to providing the normal visual acuity and CSF, wearing MiSight DFSCL also leads to better satisfaction with the appearance.

The Chromatic and Achromatic Contrast Sensitivity Function in the Far Periphery

The Chromatic and Achromatic Contrast Sensitivity Function in the Far Periphery

A new attempt to further reduce the work function of the cesiated surface: The strongest electronegative element fluorine co-adsorption with cesium on Mo (001) surface

The efficiency of hydrogen negative ion production in negative ion sources depends on the work function of the molybdenum surface. Deposition of cesium (Cs) atoms on the Mo surface reduces the work function from over 4.0 eV to about 1.50–1.80 eV. However, the Fermi level remains below the affinity level (−0.75 eV) of hydrogen negative ions. To explore further reduction methods, the work function of Cs co-adsorbed with fluorine on the Mo (001) surface was studied using DFT calculations. The results show that at 4/16 θ Cs coverage, adding fluorine can reduce the work function, achieving the lowest value of 1.40 eV at 8/16 θ F coverage. Analysis reveals a significant vacuum-inward dipole moment with fluorine-Cs co-adsorption, favorably reducing the work function. However, fluorine’s strong electronegativity also creates a surface-directed dipole moment, increasing the work function. Introducing fluorine is beneficial only at 4/16 θ Cs coverage, indicating that precise control of Cs coverage is necessary to achieve lower work functions.

Diurnal changes of corneal epithelial and stromal thickness maps and visual quality in mild form of Fuchs' endothelial corneal dystrophy.

To investigate the functional and structural daily variations in eyes with a mild form of Fuchs' endothelial corneal dystrophy (FECD). This prospective study included 30 eyes with the mild form of FECD. Subjects underwent functional and structural testing at 8 AM, 2 PM, and 8 PM. Testing included measurement of uncorrected distance visual acuity (UDVA), best corrected twilight vision (TV), and contrast sensitivity function (CSF) testing (Vista Vision Far-Pola, DMD MedTech charts). Corneal epithelial and stromal parameters were evaluated with anterior segment optical coherence tomography (AngioVue, AvantiRTVue-XR; Optovue, CA, USA). UDVA, TV, and CSF for spatial frequencies B, C, and F showed significant changes during the day, with the lowest values in the morning (P < 0.0001 for UDVA, P = 0.0109 for TV, and P < 0.0001, P = 0.0126, and P = 0.0471 for the three spatial frequencies, respectively). There was no significant change in epithelial parameters between visits. Central corneal thickness showed significant decrease during the day (P < 0.0001), as did the central stromal thickness on the 5- and 7-mm maps (P = 0.0002 and P < 0.0001, respectively), stromal thickness in the superior section of the 5-mm map (P = 0.0107), stromal thickness in the inferior section of the 7-mm map (P = 0.0002), and minimal stromal thickness on both maps (P < 0.0001). A significant negative correlation was found between central stromal thickness and TV, implying that simultaneous evaluation of corneal layers and visual quality may be useful in assessing FECD.

Vision Improvement in Keratoconus Patients Trained With Perceptual Learning: A Randomized Controlled Trial

BackgroundKeratoconus (KC) is a corneal ectasia disease in which the vision of some patients cannot achieve satisfaction by spectacle corrections. However, not everyone can embrace contact lenses to achieve better vision. Perceptual learning (PL) is a potential treatment for vision improvement in such patients. PurposeTo investigate the effectiveness and maintenance of PL on vision improvement in KC patients corrected with spectacles. DesignRandomized, double-blind clinical trial. ParticipantsThirty-five non-progressive KC patients aged 9 years or older with unsatisfied spectacle-corrected vision were enrolled. MethodsNon-progressive KC patients with best spectacle-corrected distance visual acuity (CDVA) of 0 to 1.0 logMAR (Snellen equivalent range 20/20 to 20/200) and contact lenses intolerant were enrolled. Eligible subjects were randomized into PL and control groups to receive PL and placebo training for 3 months, respectively. Spectacle-corrected visual acuity, contrast sensitivity function (CSF), stereoacuity, and visual functioning and quality of life questionnaires were measured at baseline, 3 months, and 6 months of follow-up. Statistics were analyzed following the intention-to-treat (ITT) principle. ResultsAfter 3 months of training, the CDVA of patients in the PL group improved as compared to the placebo group (0.17 ± 0.15 logMAR vs. 0.02 ± 0.06 logMAR; P = 0.0006). Eight out of seventeen (47.06 %) patients in the PL group reached CDVA improvement ≥ 2 lines (P=0.0010). This improvement persisted for at least 6 months (from baseline) as compared to the placebo group (0.17 ± 0.17 logMAR vs. 0.01 ± 0.07 logMAR; P = 0.0011). The increase of CSF in the PL group mainly was found for moderate spatial frequency (0.11 ± 0.17 log units at 3 cpd; 0.12 ± 0.19 log units at 6 cpd). Linear regression indicated that patients with worse initial CDVA achieved better gains in CDVA after PL (P = 0.009). No side effects were observed and no subjects quit because of training difficulties. ConclusionThree-month perceptual learning improved vision in KC patients and the improvement maintained after 3 months of treatment cessation. The results indicate that perceptual learning may be a promising therapy for KC patients with unsatisfied spectacle-corrected visual acuity.

Presaccadic Attention Enhances and Reshapes the Contrast Sensitivity Function Differentially around the Visual Field.

Contrast sensitivity (CS), which constrains human vision, decreases from fovea to periphery, from the horizontal to the vertical meridian, and from the lower vertical to the upper vertical meridian. It also depends on spatial frequency (SF), and the contrast sensitivity function (CSF) depicts this relation. To compensate for these visual constraints, we constantly make saccades and foveate on relevant objects in the scene. Already before saccade onset, presaccadic attention shifts to the saccade target and enhances perception. However, it is unknown whether and how it modulates the interplay between CS and SF, and if this effect varies around polar angle meridians. CS enhancement may result from a horizontal or vertical shift of the CSF, increase in bandwidth, or any combination. In addition, presaccadic attention could enhance CS similarly around the visual field, or it could benefit perception more at locations with poorer performance (i.e., vertical meridian). Here, we investigated these possibilities by extracting key attributes of the CSF of human observers. The results reveal that presaccadic attention (1) increases CS across SF, (2) increases the most preferred and the highest discernable SF, and (3) narrows the bandwidth. Therefore, presaccadic attention helps bridge the gap between presaccadic and postsaccadic input by increasing visibility at the saccade target. Counterintuitively, this CS enhancement was more pronounced where perception is better-along the horizontal than the vertical meridian-exacerbating polar angle asymmetries. Our results call for an investigation of the differential neural modulations underlying presaccadic perceptual changes for different saccade directions.

Active mutual conjoint estimation of multiple contrast sensitivity functions.

Recent advances in nonparametric contrast sensitivity function (CSF) estimation have yielded a new tradeoff between accuracy and efficiency not available to classical parametric estimators. An additional advantage of this new framework is the ability to independently tune multiple aspects of the estimator to seek further improvements. Machine learning CSF estimation with Gaussian processes allows for design optimization in the kernel, acquisition function, and underlying task representation, to name a few. This article describes a novel kernel for CSF estimation that is more flexible than a kernel based on strictly functional forms. Despite being more flexible, it can result in a more efficient estimator. Further, trial selection for data acquisition that is generalized beyond pure information gain can also improve estimator quality. Finally, introducing latent variable representations underlying general CSF shapes can enable simultaneous estimation of multiple CSFs, such as from different eyes, eccentricities, or luminances. The conditions under which the new procedures perform better than previous nonparametric estimation procedures are presented and quantified.

Psychophysics of neon color spreading: Chromatic and temporal factors are not limiting

Neon color spreading (NCS) is an illusory color phenomenon that provides a dramatic example of surface completion and filling-in. Numerous studies have varied both spatial and temporal aspects of the neon-generating stimulus to explore variations in the strength of the effect. Here, we take a novel, parametric, low-level psychophysical approach to studying NCS in two experiments. In Experiment 1, we test the ability of both cone-isolating and equiluminant stimuli to generate neon color spreading for both increments and decrements in cone modulations. As expected, sensitivity was low to S(hort-wavelength) cone stimuli due to their poor spatial resolution, but sensitivity was similar for the other color directions. We show that when these differences in detection sensitivity are accounted for, the particular cone type, and the polarity (increment or decrement), make little difference in generating neon color spreading, with NCS visible at about twice detection threshold level in all cases. In Experiment 2, we use L-cone flicker modulations (reddish and greenish excursions around grey) to study sensitivity to NCS as a function of temporal frequency from 0.5 to 8 Hz. After accounting for detectability, the temporal contrast sensitivity functions for NCS are approximately constant or even increase over the studied frequency range. Therefore there is no evidence in this study that the processes underlying NCS are slower than the low-level processes of simple flicker detection. These results point to relatively fast mechanisms, not slow diffusion processes, as the substrate for NCS.

Impaired Visual Function in Posterior Vitreous Detachment Assessed With the Active-Learning Quantitative Contrast Sensitivity Function Test.

Introduction: To investigate whether there is visual function impairment in patients with posterior vitreous detachment (PVD) using the active-learning quantitative contrast sensitivity function test. Methods: In this cross-sectional study, contrast sensitivity was measured in eyes with PVD and eyes without PVD using the quantitative contrast sensitivity function algorithm on the Adaptive Sensory Technology platform. Outcomes included the area under the log contrast sensitivity function curve, contrast acuity, and contrast sensitivity thresholds at 1 to 18 cycles per degree (cpd). Snellen visual acuity (VA) was also measured. Mixed-effects multiple linear regression analyses were performed to evaluate the association between the presence of PVD and visual function, controlling for age and lens status. Results: The cohort comprised 232 healthy eyes of 205 participants; of these, 80 eyes of 69 patients had PVD. There was no significant association between VA and PVD presence. However, PVD was significantly associated with decreased contrast sensitivity thresholds at 1.5 cpd (β, -0.058; P = .003) and 3 cpd (β, -0.067; P = .004). Contrast sensitivity thresholds at lower (1 cpd) or higher (6, 12, 18 cpd) spatial frequencies did not significantly correlate with PVD presence. Even in the subgroup of symptomatic PVD eyes, VA was not significantly decreased, while quantitative contrast sensitivity function outcomes showed visual function deficits at low spatial frequencies (1.5 cpd and 3 cpd). Conclusions: Contrast sensitivity measured with the quantitative contrast sensitivity function test showed visual function deficits in eyes with PVD that would have been missed with VA testing alone. Incorporating this test in the retina clinic might offer a more comprehensive functional assessment of eyes with PVD, serving as an adjunct outcome metric in clinical decision-making.