A Colour Contrast Assessment System: Design for People with Visual Impairment (original) (raw)
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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.
Use of subjective and objective criteria to categorise visual disability
Indian Journal of Ophthalmology, 2014
Context: Visual disability is categorised using objective criteria. Subjective measures are not considered. Aim: To use subjective criteria along with objective ones to categorise visual disability. Settings and Design: Ophthalmology outpatient department; teaching hospital; observational study. Material and Methods: Consecutive persons aged >25 years, with vision <20/20 (in one or both eyes) due to chronic conditions, like cataract and refractive errors, were categorized into 11 groups of increasing disability; group-zero: normal range of vision, to group-X: no perception of light, bilaterally. Snellen's vision; binocular contrast sensitivity (Pelli-Robson chart); automated binocular visual field (Humphrey; Esterman test); and vision-related quality of life (Indian Visual Function Questionnaire-33; IND-VFQ33) were recorded. Statistical Analysis: SPSS version-17; Kruskal-wallis test was used to compare contrast sensitivity and visual fields across groups, and Mann-Whitney U test for pair-wise comparison (Bonferroni adjustment; P < 0.01). One-way ANOVA compared quality of life data across groups; for pairwise significance, Dunnett T3 test was applied. Results: In 226 patients, contrast sensitivity and visual fields were comparable for differing disability grades except when disability was severe (P < 0.001), or moderately severe (P < 0.01). Individual scales of IND-VFQ33 were also mostly comparable; however, global scores showed a distinct pattern, being different for some disability grades but comparable for groups III (78.51 ± 6.86) and IV (82.64 ± 5.80), and groups IV and V (77.23 ± 3.22); these were merged to generate group 345; similarly, global scores were comparable for adjacent groups V and VI (72.53 ± 6.77), VI and VII (74.46 ± 4.32), and VII and VIII (69.12 ± 5.97); these were merged to generate group 5678; thereafter, contrast sensitivity and global and individual IND-VFQ33 scores could differentiate between different grades of disability in the five new groups. Conclusions: Subjective criteria made it possible to objectively reclassify visual disability. Visual disability grades could be redefined to accommodate all from zero-100%.
SAGE Open, 2020
The present study aimed to investigate the appropriate level of value contrast in built environments, including the ratio of dark value to light value color, to enable people with low vision to distinguish elements more readily from the surroundings. The study included a total of 20 participants from four locations in Texas. Participants received a two-part questionnaire: Part 1 recorded demographic information including age, gender, and visual acuity; Part 2 presented the central questions of the study relating to given images. All of the participants agreed that high value contrast images with at least 60% variance between the dark and light values were very easy to see. Participants also indicated that medium value contrast images with a variance of 30% were recognizable. Most of the participants also indicated a preference for light value to dark value in a built environment.
Proceedings of the 21st Congress of the International Ergonomics Association (IEA 2021), 2021
The qualities of the built environment impact on the ability of people with vision impairment to move safely through the environment. It is important to revisit the evidence of the relationship between vision and the visibility of elements in the built environment to ensure accessibility standards and design guidelines are consistent with the latest evidence base. This paper reviews mixed method (qualitative and quantitative) research into visual and non-visual factors known to be implicated in injurious incidents in people with vision impairment. The evidence base for the visibility of simulated and real environmental elements such as stairs, doors, door handles, light switches, tactile ground surface indicators, traffic cones, road line markings and pedestrians will be reviewed. The evidence suggests that luminance contrasts of approximately 2.5× current contrast standards, as current standards vary, would allow people with up to severe vision impairment to see objects of the dimensions of tactile ground surface indicators with ease. If people who are categorised as being blind by WHO are considered, about 3× current contrast standards may be required. If lower contrasts are used, alternative provisions should be made to assist people with vision impairment to navigate the space safely.
Eye, 2020
Background Registration as sight impaired allows access to services important for patients. The rates of sight impairment due to visual field loss are underestimated. Previous work has shown that evaluation of visual field defects in both eyes produces poor agreement among ophthalmologists for categorisation of patients as eligible for sight impairment registration. Aim To evaluate the impact of binocular summation of both eye glaucomatous visual field defects on agreement for sight impairment registration. Methods Thirty consultant ophthalmologists (Graders), graded 50 glaucomatous visual field sets. Each consisted of both monocular fields and summated binocular plots. Graders classified the visual field sets as sight impaired (SI), severely sight impaired (SSI) or neither. Trichotomous, (SI, SSI or no sight impairment) and dichotomous (any sight impairment versus no sight impairment) concordance values were estimated for the group of graders as a whole and for glaucoma and non-glaucoma experts. Results For trichotomous analysis the overall kappa agreement rate was 0.29; for dichotomous analysis it was 0.40. There was no material difference between glaucoma experts and non-experts. Conclusion Overall agreement was modest. Grading for SI showed the poorest levels of agreement. Using binocular fields does not appear to improve concordance for sight impairment registration. Moreover, there is no difference in agreement between glaucoma and non-glaucoma experts. An overall score for visual disability using mean deviation may be a more pragmatic approach.
Visual function tests, eye disease and symptoms of visual disability: a population-based assessment
Clinical and Experimental Ophthalmology, 2000
Purpose: To examine associations between eye disease and tests of visual function with self-reported visual disability. Methods: The Blue Mountains Eye Study is a cross-sectional census-based survey of eye disease in two postcode areas in the Blue Mountains, west of Sydney, Australia. Of 4433 eligible residents, 3654 (82.4%) participated. Subjects had a detailed eye examination, including tests of visual acuity, contrast sensitivity, disability glare and visual field. Lens and retinal photographs were taken and graded according to standardized protocols for presence of cataract, early and late age-related maculopathy, glaucoma, diabetic retinopathy, retinal vein occlusion and other eye diseases. An interviewer-administered questionnaire included questions about perception of visual disability. Results: Scores on all tests of visual function significantly decreased with age (P < 0.0001). This decrease persisted for all tests except disability glare after excluding subjects with identifiable eye disease. The presence of one or more eye diseases was significantly associated with all (self-reported) measures of visual disability (trouble driving at night, difficulty recognizing a friend across the street, reading a newspaper or recognizing detail on television); mixed cataract (cortical and nuclear, or posterior subcapsular and nuclear) was associated with trouble driving at night and difficulty recognizing a friend across the street. A 10-letter (two-line) decrease in best corrected or presenting visual acuity was significantly associated with all selfreported measures of visual disability, as was a two-step decrease in contrast sensitivity. A five-point increase in points missing in the visual field was weakly but significantly associated with all self-reported measures of visual disability except trouble driving at night. Conclusions: Visual function declines with age. Impaired visual function was strongly, and eye disease relatively weakly associated with reports of visual disability.