Foveal detection thresholds for luminance-modulated (LM) and contrast-modulated (CM) blobs in the presence of fixed modulation, laterally placed noise blobs (separations of 0-6 degrees ) were measured in four observers with normal vision. Detection thresholds measured for LM blobs placed between highly visible LM flankers (111) and for CM blobs placed between highly visible CM flankers (222) produces a similar pattern of lateral interaction effects, i.e. masking where the stimuli overlap and facilitation for separations of 4-8x blob sd units. The region of facilitation is not matched by shallow psychometric function slopes. Detection thresholds measured for LM blobs placed between highly visible CM flankers (212) are generally facilitatory but relatively raised for separations of 0.5-2 degrees . For CM blobs placed between highly visible LM flankers (121), facilitation is stronger in the 0.5-2 degrees region. A significant correlation between thresholds and psychometric function slopes is found only for the 212 condition. We propose a model with two separate but interacting processing streams for the detection of LM and CM targets that may engage different cortical loci.
Foveal detection thresholds for LM and CM Gaussian blobs in the presence of visible, laterally placed blobs (separations of 0-6°) were measured monocularly and dichoptically in observers with normal vision. In the monocular and dichoptic viewing conditions, masking occurs for overlapping blobs, followed by facilitation when they are completely separated (2-8 blob sd units under monocular conditions and 4-12 blob sd units under dichoptic conditions). For LM blobs, facilitation of 24.1±0.07% is demonstrated dichoptically, less than the 57.0±0.06% demonstrated monocularly. For CM blobs, more robust facilitation of 39.0±0.02% is demonstrated dichoptically, slightly more than the 34.6±0.1% demonstrated monocularly. Lateral facilitation is thus not purely a monocular phenomenon. More robust dichoptic facilitation for CM stimuli suggests a more binocular locus for their neural processing.
Letter recognition is regularly assessed in clinical and experimental settings using a set of letters, either with single letters that are presented successively or with a string of letters that is presented within a single trial. The aim of the present study was to determine resolution thresholds and contrast thresholds for the recognition of each of 7 Sheridan−Gardiner letters that were presented at the central fovea and different retinal eccentricities. Using a method of constant stimuli with a 7-alternative forced-choice paradigm, we measured resolution thresholds for high-contrast letters and contrast thresholds for fixed-sized letters. Measurements were made at the central fovea and at 0.5, 1.0, 2.0, and 4.0° in the lower visual field. Results indicated that the resolution threshold for high-contrast letters (in logMAR) increased approximately linearly with increasing eccentricity (slope = .13, SD = .01). Separate analyses for each letter revealed that their resolution thresholds at a particular eccentricity differed by up to .43 logMAR. However, contrast thresholds for individual letters, scaled for eccentricity, for all retinal locations tested did not differ significantly. Our findings have implications in clinical settings where measurements of visual acuity are performed with a limited number of letters, but they complement the use of low-contrast charts for measurements of contrast sensitivity for letter recognition in the periphery.
Contrast-modulated (CM) stimuli are processed by spatial mechanisms that operate at larger spatial scales than those processing luminance-modulated (LM) stimuli and may be more prone to deficits in developing, amblyopic, and aging visual systems. Understanding neural mechanisms of contour interaction or crowding will help in detecting disorders of spatial vision. In this study, contour interaction effects on visual acuity for LM and CM C and bar stimuli are assessed in normal foveal vision. In Experiment 1, visual acuity is measured for all-LM and all-CM stimuli, at ∼3.5× above their respective modulation thresholds. In Experiment 2, visual acuity is measured for Cs and bars of different type (LM C with CM bars and vice versa). Visual acuity is degraded for CM compared with LM Cs (0.46 ± 0.04 logMAR vs. 0.18 ± 0.04 logMAR). With nearby bars, CM acuity is degraded further (0.23 ± 0.01 logMAR or ∼2 lines on an acuity chart), significantly more than LM acuity (0.11 ± 0.01 logMAR, ∼1 line). Contour interaction for CM stimuli extends over greater distances (arcmin) than it does for LM stimuli, but extents are similar with respect to acuities (∼3.5× the C gap width). Contour interaction is evident when the Cs and bars are defined differently: it is stronger when an LM C is flanked by CM bars (0.17 ± 0.03 logMAR) than when a CM C is flanked by LM bars (0.08 ± 0.02 logMAR). Our results suggest that contour interaction for foveally viewed acuity stimuli involves feature integration, such that the outputs of receptive fields representing Cs and bars are combined. Contour interaction operates at LM and CM representational stages, it can occur across stage, and it is enhanced at the CM stage. Greater contour interaction for CM Cs and bars could hold value for visual acuity testing and earlier diagnosis of conditions for which crowding is important, such as in amblyopia.
Visual conditions such as anisometropia, monovision and monocular undercorrection affect the combination of visual input from both eyes. This study investigated the effects of monocular blur, in binocularly normal
Visual-motor integration (VMI) is related to children’s academic performance and school readiness. VMI scores measured using the Beery-Bucktenicka Developmental Test of Visual-Motor Integration (Beery-VMI) can differ due to differences in cultural and socioeconomic backgrounds. This study compared the VMI scores of Malaysian preschoolers with the corresponding US norms and determined the association between their VMI scores and socioeconomic factors. A cross-sectional study was conducted among 435 preschoolers (mean age: 5.95±0.47 years; age range: 5.08–6.83 years) from randomly selected public and private preschools. VMI scores were measured using Beery-VMI in the preschools’ classrooms. Information on the socioeconomic characteristics of the preschoolers was obtained using a parent-report questionnaire. One sample t-test was used to compare their VMI scores with the corresponding US norms. Multivariate logistic regression models were used to explore the influence of socioeconomic factors on the preschoolers’ VMI scores. Overall, Malaysian preschoolers’ VMI performance was similar to the US standardized norms (p>0.05). Children from low-income families were twice likely to obtain lower than average VMI scores than those from higher-income families (OR = 2.47, 95%CI 1.05, 5.86). Children enrolled at public preschools were more likely to obtain a lower than average VMI score than those who enrolled at private preschools (OR = 2.60, 95%CI 1.12, 6.06). Children who started preschool at the age of six were more likely to obtain lower than average VMI scores than those who started at an earlier age (OR = 4.66, 95%CI 1.97, 11.04). Low maternal education level was also associated with lower than average VMI score (OR = 2.60, 95%CI 1.12, 6.06). Malaysian preschoolers’ Beery-VMI performance compared well to their US counterparts. Some socioeconomic factors were associated with reduced VMI scores. Those from disadvantaged socioeconomic backgrounds are more likely to have reduced VMI performance, potentially adversely affecting their school readiness, cognitive performance, and future academic achievements.
Many East Asians apply double eyelid tape to create the double eyelid effect temporarily as a means of increasing their beauty. This study evaluated the effects of four-week wear of double eyelid tape on anterior ocular health in young adult women with single eyelids. Twenty-nine participants who met the inclusion criteria were recruited. The participants’ anterior ocular health was examined including blinking characteristics (blink pattern and blink rate), ocular surface health (presence of corneal abrasion, corneal staining, conjunctival staining, corneal curvatures, meibomian gland dysfunction), tear break up time, intraocular pressure, and subjective comfort level. Participants were required to apply the double eyelid tape for at least eight hours a day and five days a week for four weeks. The parameters were re-measured at the end of each week. There was a significant increase in conjunctival staining, corneal staining, and meibomian gland dysfunction, with a significant reduction in tear break-up time and intraocular pressure. By week 3, all participants had incomplete blinks. There was no significant change in symptoms and subjective comfort level reported. Therefore, patients and eye care practitioners should be aware of the potential implications of double eyelid tape wear on ocular health, with no significant change in subjective comfort.
Postpartum depression (PPD) is one of the mental health complications that may arise following childbirth. This cross-sectional study explores the association between socioeconomic factors and PPD literacy with PPD incidence in 350 participants (mean age: 30.58±4.72 years) at one to six months postpartum, who attended the Kuala Lumpur Health Clinic from May to October 2020. PPD incidence and literacy were assessed using the validated Malay versions of the Edinburgh Postpartum Depression Scale (EPDS) and the Postpartum Depression Literacy Scale (PoDLiS), respectively. The participants’ socioeconomic characteristics were collected using a self-administered questionnaire. Chi-square tests were performed to determine the association between these factors and PPD incidence. Binary logistic regression models were used to determine the odds ratios (OR). The incidence of postpartum depressive symptoms was 14.29%. Those with low household income were twice likely to have PPD symptoms (OR:2.58, 95% CI:1.23–5.19; p = 0.01) than those with higher incomes. Unemployment (i.e., participants who were housewives/homemakers) was associated with higher PPD incidence (Χ2(2, 350) = 6.97, p = 0.03), but it was not a significant PPD predictor. In conclusion, PPD incidence in the sample of Kuala Lumpur postpartum mothers is significantly associated with low household income. Other socioeconomic characteristics, including PPD literacy, were not significant predictors of PPD incidence.
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