Perception of Curves

1975 ◽  
Vol 41 (2) ◽  
pp. 495-504 ◽  
Author(s):  
Leonard Zusne
Keyword(s):  
Visual Acuity ◽  
Problem Solving ◽  
Discrimination Problem ◽  
Luminance Contrast ◽  
Perceptual Task ◽  
Two Dimensional ◽  
Random Polygons ◽  
Low Luminance ◽  
Distance Vision

In 4 experiments, in which 66 subjects participated, the perception of 6 types of curved contours in two-dimensional shapes was studied. Random polygons and their curvilinear transformations were presented for detection under low-luminance contrast conditions, oddity-type discrimination problem solving, tachistoscopic identification, and identification involving visual acuity in distance vision. In all experiments curvature affected perception at statistically significant levels, but the extent of this effect was a function of (1) the locus and direction of curvature, (2) the level of compactness-jaggedness of the figure, and (3) the nature of the perceptual task. Shapes with acute corners were more easily perceived than shapes with curved corners. Within these two classes of shapes, those with convex sides were perceived as having greater curvedness than those with concave contours. However, the degree to which curvature affected response was determined primarily by the nature of the perceptual task.

scholarly journals Visual performance in a flight simulator: multifocal intraocular lenses in pilots

2018 ◽  
Vol 3 (1) ◽  
pp. e000139
Author(s):  
Lee Lenton
Keyword(s):  
Visual Acuity ◽  
Contrast Sensitivity ◽  
Luminance Contrast ◽  
Intraocular Lenses ◽  
Visual Performance ◽  
Flight Simulator ◽  
Night Time ◽  
Multifocal Intraocular Lenses ◽  
Low Luminance ◽  
Visual Tasks

ObjectiveTo compare the performance of adults with multifocal intraocular lenses (MIOLs) in a realistic flight simulator with age-matched adults with monofocal intraocular lenses (IOLs).Methods and AnalysisTwenty-five adults ≥60 years with either bilateral MIOL or bilateral IOL implantation were enrolled. Visual function tests included visual acuity and contrast sensitivity under photopic and mesopic conditions, defocus curves and low luminance contrast sensitivity tests in the presence and absence of glare (Mesotest II), as well as halo size measurement using an app-based halometer (Aston halometer). Flight simulator performance was assessed in a fixed-based flight simulator (PS4.5). Subjects completed three simulated landing runs in both daytime and night-time conditions in a randomised order, including a series of visual tasks critical for safety.ResultsOf the 25 age-matched enrolled subjects, 13 had bilateral MIOLs and 12 had bilateral IOLs. Photopic and mesopic visual acuity or contrast sensitivity were not significantly different between the groups. Larger halo areas were seen in the MIOL group and Mesotest values were significantly worse in the MIOL group, both with and without glare. The defocus curves showed better uncorrected visual acuity at intermediate and near distances for the MIOL group. There were no significant differences regarding performance of the vision-related flight simulator tasks between both groups.ConclusionsThe performance of visually related flight simulator tasks was not significantly impaired in older adults with MIOLs compared with age-matched adults with monofocal IOLs. These findings suggest that MIOLs do not impair visual performance in a flight simulator.

Comparing estimated and actual visual acuity at high and low luminance

2006 ◽  
Author(s):  
Johnell O. Brooks ◽  
Richard A. Tyrrell ◽  
Benjamin R. Stephens
Keyword(s):  
Visual Acuity ◽  
Low Luminance

Color stimuli perception in presence of light scattering

2006 ◽  
Vol 23 (3-4) ◽  
pp. 597-601 ◽  
Author(s):  
MARIS OZOLINSH ◽  
MICHÉLE COLOMB ◽  
GATIS IKAUNIEKS ◽  
VARIS KARITANS
Keyword(s):  
Visual Acuity ◽  
Light Scattering ◽  
Luminance Contrast ◽  
White Background ◽  
Color Contrast ◽  
Entire Area ◽  
Red Color ◽  
Blue Component ◽  
Different Color ◽  
Landolt C

Perception of different color contrast stimuli was studied in the presence of light scattering: in a fog chamber in Clermont-Ferrand and in laboratory conditions where light scattering of similar levels was obtained, using different light scattering eye occluders. Blue (shortest wavelength) light is scattered in fog to the greatest extent, causing deterioration of vision quality especially for the monochromatic blue stimuli. However, for the color stimuli presented on a white background, visual acuity in fog for blue Landolt-C optotypes was higher than for red and green optotypes on the white background. The luminance of color Landolt-C optotypes presented on a LCD screen was chosen corresponding to the blue, green, and red color contributions in achromatic white stimuli (computer digital R, G, or B values for chromatic stimuli equal to RGB values in the achromatic white background) that results in the greatest luminance contrast for the white–blue stimuli, thus advancing the visual acuity for the white-blue stimuli. Besides such blue stimuli on the white background are displayed with a uniform, spatially unmodulated distribution of the screen blue phosphor emission over the entire area of the screen including the stimulus C optotype area. It follows that scattering, which has the greatest effect on the blue component of screen luminance, has the least effect on the perception of white–blue stimuli.

scholarly journals Contrast sensitivity and visual acuity under low light conditions in macular telangiectasia type 2

2018 ◽  
Vol 103 (3) ◽  
pp. 398-403 ◽  
Author(s):  
Simone Müller ◽  
Tjebo F C Heeren ◽  
Roberto Bonelli ◽  
Marcus Fruttiger ◽  
Peter Charbel Issa ◽  
...  
Keyword(s):  
Visual Acuity ◽  
Contrast Sensitivity ◽  
Neutral Density Filter ◽  
Light Conditions ◽  
Low Light ◽  
Cross Sectional ◽  
Macular Telangiectasia ◽  
Low Luminance ◽  
Macular Telangiectasia Type 2

Background/AimMacular pigment optical density (MPOD) is centrally depleted early on in macular telangiectasia type 2 (MacTel). Contrast sensitivity (CS) might be related to MPOD, and thus impaired in early MacTel. The effect of low luminance was assessed on both CS and best corrected visual acuity (BCVA).MethodsThis is a cross-sectional study. Pelli-Robson charts were used for CS testing at 1 m in photopic (110 lux) and mesopic (1 lux) conditions. BCVA was tested with ETDRS charts and low luminance visual acuity (LLVA) with a 2.0 log unit neutral density filter. MPOD was obtained with dual-wavelength autofluorescence.ResultsOne hundred and three eyes of 52 patients with MacTel (mean±SD age 62.9±10.2, range 35–77) were compared with 34 healthy eyes of 17 controls (mean±SD age 65.2±7.4, range 53–78). CS was significantly lower in the eyes with MacTel. This impairment was higher in low light conditions (low light contrast sensitivity (LL-CS)). Eyes at the early stages of MacTel had significantly lower LL-CS than controls, but normal (photopic) CS. The results were similar but less pronounced for BCVA/LLVA. Decrease in CS was correlated with loss of MPOD.ConclusionsLow light conditions have a detrimental effect on visual performance in MacTel. Impaired CS might correlate with MPOD depletion as a pathognomonic finding in MacTel. Functional impairment might precede structural disintegration, indicating dysfunction at the cellular level. The applied tests might be useful as additional functional assessments in clinical routine and as outcome measures in future interventional clinical trials.

The relationship between two-dimensional self-esteem and problem solving style in an anorexic inpatient sample

2006 ◽  
Vol 15 (1) ◽  
pp. 70-77 ◽  
Author(s):  
Gillian Paterson ◽  
Kevin Power ◽  
Alex Yellowlees ◽  
Katy Park ◽  
Louise Taylor
Keyword(s):  
Problem Solving ◽  
Self Esteem ◽  
Two Dimensional ◽  
Problem Solving Style ◽  
The Relationship

scholarly journals Use of spectacles for distance vision: coverage, unmet needs and barriers in a rural area of North India

2019 ◽  
Vol 19 (1) ◽  
Author(s):  
Sumit Malhotra ◽  
Mani Kalaivani ◽  
Ramashankar Rath ◽  
Manya Prasad ◽  
Praveen Vashist ◽  
...  
Keyword(s):  
Visual Acuity ◽  
Associated Factors ◽  
Unmet Needs ◽  
Multivariable Analysis ◽  
Unmet Need ◽  
Cross Sectional Study ◽  
North India ◽  
Multivariable Logistic Regression Analysis ◽  
Cross Sectional ◽  
Distance Vision

Abstract Background Uncorrected refractive errors contribute enormously to the burden of avoidable visual impairment worldwide. There is a huge disparity in different parts of the globe in context to spectacle coverage for distance vision. This study was undertaken with objectives of determining prevalence of spectacle coverage, unmet needs and associated factors among adults in a rural community of north India. Methods A community-based cross-sectional study was carried out within selected clusters of Jhajjar district of Haryana. All participants aged > 15 years underwent visual acuity assessment by LogMAR “E” screening chart. Participants with presenting visual acuity < 6/12 in any eye and all current spectacle users underwent detailed ophthalmic examination and refraction. Additional details about spectacles, barriers for their use and willingness to pay for them were collected. Participants with met and unmet need for spectacle use at visual acuity > 6/12 was computed. These are reported as proportions with 95% confidence intervals. Associated factors with unmet need were determined using bivariable and multivariable logistic regression analysis. Results A total of 6910 participants were examined. The current spectacle use was 7.5% (95% Confidence Interval CI: 6.5, 8.7). The spectacle coverage was found in 33.3% (95% CI: 30.0, 36.7) participants among those in need. The unmet need was found in 10.8% of participants (95% CI: 10.1, 11.6). On multivariable analysis, odds of unmet need was associated with age, gender, level of education and marriage status. The most common barrier for refractive correction was lack of perceived need for refraction and its correction. Conclusion There is substantial unmet need for distance vision spectacles in this population. It is imperative that multi-component intervention be implemented to improve spectacle coverage in this rural north Indian setting.

Association between central retinal thickness and low luminance visual acuity in early age-related macular degeneration

2020 ◽  
pp. 112067212096874
Author(s):  
María Cinta Puell ◽  
Francisco Javier Hurtado-Ceña ◽  
María Jesús Pérez-Carrasco ◽  
Inés Contreras
Keyword(s):  
Visual Acuity ◽  
Macular Degeneration ◽  
Retinal Thickness ◽  
Central Area ◽  
Age Related Macular Degeneration ◽  
Central Retinal Thickness ◽  
Cross Sectional ◽  
Age Related ◽  
Low Luminance ◽  
Sd Oct

Purpose/Aim: To examine whether central retinal thickness (CRT) is related to mesopic visual acuity (VA) and low luminance deficit (LLD, difference between photopic and mesopic VA) in eyes with early and intermediate age-related macular degeneration (AMD). Materials and Methods: In a cross-sectional study, 50 pseudophakic subjects older than 63 years were divided into three groups (no AMD, early AMD and intermediate AMD). Spectral domain optical coherence tomography (SD-OCT) was used to measure CRT in the 1 mm-central-area. Best-corrected distance VA was measured under photopic or mesopic luminance conditions and LLD calculated. Subjects were stratified by VA impairment to compare CRTs across these groups. Relationships were examined by stepwise multiple linear regression. Results: No significant differences in mean CRT, photopic and mesopic VA or LLD were detected between the groups no AMD, early AMD and intermediate AMD. However, mean CRTs were 20 microns and 18 microns thicker in the eyes with impaired mesopic VA (> 0.3 logMAR) and impaired LLD (⩾ 0.3 logMAR) compared to the eyes with non-impaired VA or LLD respectively (both p < 0.01). CRT and mesopic pupil size were independent predictors of mesopic VA ( p  = 0.001). CRT emerged as the only independent predictor of LLD ( p  = 0.004). Conclusions: Increased CRT was linked to worse retinal function when measured under mesopic conditions in eyes without AMD and eyes with early to intermediate AMD. SD-OCT imaging combined with VA measurements under low luminance conditions could be a useful tool to detect early AMD.

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