Functional vision barriers: a new concept analyzed in terms of human visual performance (original) (raw)
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Research Square - Research Square, 2022
Purpose: To investigate the effect of lters and illumination on contrast sensitivity in persons with cataract, pseudophakia, maculopathy and glaucoma to provide a guide for eye care providers in low vision rehabilitation. Materials and methods: A within-subjects experimental design with a counterbalanced presentation technique was employed in this study. The contrast sensitivity of eyes with cataract, pseudophakia, maculopathy and glaucoma were measured with lters (no lter, yellow, pink and orange) combined with increasing illumination levels (100lux, 300lux, 700lux and 1000lux) using the SpotChecks TM contrast sensitivity chart. The data was analyzed using descriptive statistics and two-way repeated measures ANOVA. Results: The yellow lter in combination with 100lux signi cantly (p<0.01) improved contrast sensitivity by approximately 6.5% among eyes with cataract. There was also a signi cant interaction between illumination and lters, with Huynh-Feldt correction, F (7.20, 230.23) = 2.06, p=0.04. Eyes with pseudophakia performed best at 1000lux with or without lters. In eyes with maculopathy, the yellow lter combined with 300lux gave the best improvement in CS from 1.33-1.45logCS (p=0.01). Illumination of 1000lux without a lter improved CS best in eyes with Glaucoma. Conclusion: The effect of lters and illumination on contrast sensitivity is dependent on the cause of contrast sensitivity loss. Eye care professionals must consider the underlying cause of visual impairment if patient speci c care is to be rendered.
Impairment of contrast sensitivity function (CSF) as a measure of disability glare
Investigative ophthalmology & visual science, 1986
A method for quantitative measurements of disability glare in clinical practice is presented. Glare is induced by a circular fluorescent tube which surrounds a sinusoidal grating displayed on a monitor. The threshold contrast that is needed for detection of the grating is measured with and without presence of the glare light. This is repeated for several different spatial frequencies. The discrepancy between the contrast sensitivity function (CSF) obtained with and without glare light was used to calculate the glare score (n) as a measure of disability glare. This was done for normals and cataract patients. The results show that an increasing glare score is related to an increase in turbidity of the optic media, while visual acuity had a weak correlation to the glare score. We also studied the relation glare score versus luminance and found that normals had a glare score that was almost independent of luminance level, while the cataract patients had a marked decrease in glare sensitivity when the luminance decreased. Most patients had a glare score that corresponded to their glare problems. These findings indicate a potential for using this psychophysical disability glare test method in industry, transport, and clinical ophthalmology. Some sources of methodological error inherent in the test method are evaluated and discussed. Invest Ophthalmol Vis
A note on image degradation, disability glare, and binocular vision
Journal of Modern Optics, 2013
Disability glare due to scattering of light causes a reduction in visual performance due to a luminous veil over the scene. This causes problem such as contrast detection. In this note, we report a study of the effect of this veiling luminance on human stereoscopic vision. We measured the effect of glare on the horopter measured using the apparent fronto-parallel plane (AFPP) criterion. The empirical longitudinal horopter measured using the AFPP criterion was analyzed using the so-called analytic plot. The analytic plot parameters were used for quantitative measurement of binocular vision. Image degradation plays a major effect on binocular vision as measured by the horopter. Under the conditions tested, it appears that if vision is sufficiently degraded then the addition of disability glare does not seem to significantly cause any further compromise in depth perception as measured by the horopter.
A comparison between different light sources induced glare on perceived contrast
Light & Engineering, 2012
1The aim of this research is to compare the influ- ence of two different luminous sources (incandescent light and LED light) on perceived contrast of ob- jects in a disability glare context. About 25 subjects were involved in an experiment in order to monitor the variations in their contrast perception threshold, with and without glare sources, using a calibrated computer LCD display. In this first phase the spectral influence is investigate. Typical applications of this research results, could be road and tunnel lighting requirements on disability glare restrictions when LED sources are used. Keywords: subjective experiment, contrast threshold, disability glare, LED
Acta medica Lituanica, 2014
Background. As people age, their vision becomes less clear; they can clearly see big objects but experience problems discerning minor things and minor details. The functional acuity contrast test is a very sensitive method used for visual system evaluation which may help to detect the beginning of the disease in case the visual acuity is still normal. Purpose. To determine functional acuity contrast sensitivity in young and in middle age healthy persons at the day time with and without glare. Materials and methods. We examined 40–49 yrs (Group 1), and 50– 59 yrs (Group 2) healthy persons. The typical Snellen chart (the direction of the gap in Landolt C) was used for the non-corrected and the bestcorrected visual acuity testing. Functional acuity contrast sensitivity was measured employing a Ginsburg Box, VSCR- CST-6500, at the day time with and without glare. Results. Functional acuity contrast sensitivity remained very similar in the age groups of 40–49 years and 50–59 years. Howe...
An Experimental Study on the Effect of Visual Tasks on Discomfort Due to Peripheral Glare
LEUKOS The Journal of the Illuminating Engineering Society of North America , 2019
This article concerns discomfort due to sources of glare in the peripheral visual field. A visual task is needed to maintain foveal fixation at a known location, and in past studies the tasks have ranged from a simple fixation mark to a task requiring greater cognitive attention such as reading. It was hypothesized that these different approaches to control visual attention would influence the evaluation of discomfort. This article reports an experiment that compared evaluations of discomfort when using the two visual tasks, a simple circle and a pseudo-text reading task, and two procedures, category rating and luminance adjustment. The results from both procedures confirmed the hypothesis: a lower degree of discomfort was expressed in the pseudo-text trials than in trials with the circular fixation mark.
Visual Task Difficulty and Temporal Influences in Glare Response
Building and Environment, 2016
The literature suggests that glare sensation may be influenced by visual task difficulty. Previous research by the authors provided reasons to infer that the perceived level of visual discomfort may vary with time of day and be affected by temporal and personal factors. The study presented here explores the postulated relationships between visual task difficulty, temporal variables, and glare response as the day progresses. Under controlled laboratory conditions, twenty subjects were exposed to a constant artificial source luminance at four times of day and gave glare sensation votes while completing twelve visual tasks of various difficulties. Self-assessments of temporal variables (fatigue, food intake, caffeine ingestion, mood, previous daylight exposure and sky condition) were provided by test subjects together with their glare judgements. Statistical analysis of responses confirmed that the time interval between test sessions showed a direct relationship to the increased tolerance to artificial source luminance along the day. The temporal variation of glare response was found to be influenced by the difficulty in extracting information from the visual stimulus. Moreover, statistically significant and substantive evidence was detected of a direct effect of fatigue and caffeine ingestion, and an inverse influence of food intake, on reported glare sensation. Consideration of inferential results from all test sessions led to hypothesise that some temporal variables may interact with each other and significantly affect the variation of glare response at different times of day.
Research on minimum illumination as a function of visual performance
Energy and Buildings, 2004
The objective of this research is to find minimum illuminance level such that a visual task (in this case is reading) still can be done properly. The reading object in this research is sentences (written in Bahasa Indonesia) and printed in Times New Roman font on a white A4 paper. Three factors are observed, i.e. font size, luminance contrast (between letters and paper), and reading distance. Measurements were made of the minimum illumination that was needed by subjects, such that they still can read the object properly. The experiment was done in a dark room and the illuminance level on the object from a lamp was adjusted by using a dimmer device. The results of this experiment show that the lowest minimum illuminance of 0.13 lx (for reading object with font size 16, luminance contrast of 0.93, and distance of 60 cm) and the highest of 15.32 lx (for reading object with font size 8, luminance contrast of 0.55, and distance of 100 cm). By using analysis of variance method, it can be shown that reading distance is the most influential factor for the minimum illuminance level, and then followed by dimension and luminance contrast.
Archives of Ophthalmology
To determine the association between performance on selected tasks of everyday life and impairment in visual acuity and contrast sensitivity. Methods: Visual acuity and contrast sensitivity were obtained on a population-based sample of 2520 older African American and white subjects. Performance was assessed on mobility, daily activities with a strong visual component, and visually intensive tasks. Disability was defined as performance less than 1 SD below the mean. Receiver operating characteristic curve analyses were used to evaluate the sensitivity and specificity of thresholds in acuity and contrast loss for determining disability. Results: Both visual acuity and contrast sensitivity loss were associated with decrements in function. The relationship of function to the vision measures was mostly linear, therefore, receiver operating characteristic curves were not helpful in identifying cutoff points for predicting disabilities. For mobility tasks, most persons were not disabled until they had significant acuity loss (logMAR visual acuity Ͼ1.0 or Ͻ20/200) or contrast sensitivity loss (0.9 log units contrast sensitivity). For heavily visually intensive tasks, like reading, visual acuity worse than 0.2 logMAR (20/30) or contrast sensitivity worse than 1.4 log units was disabling. Conclusions: Both contrast sensitivity and visual acuity loss contribute independently to deficits in performance on everyday tasks. Defining disability as deficits in performance relative to a population, it is possible to identify visual acuity and contrast loss where most are disabled. However, the cutoff points depend on the task, suggesting that defining disability using a single threshold for visual acuity or contrast sensitivity loss is arbitrary.