Computer monitor pixellation and Landolt C visual acuity

2021 ◽  
Author(s):  
Andrew Carkeet ◽  
Lucas Lister ◽  
Yee Teng Goh
Keyword(s):  
Visual Acuity ◽  
Landolt C

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.

The Accuracy of Drivers' Judgments of the Effects of Headlight Glare on Their Own Visual Acuity

Perception ◽  
10.1068/p7814 ◽  
2014 ◽  
Vol 43 (11) ◽  
pp. 1203-1213 ◽  
Author(s):  
Ashley A Stafford Sewall ◽  
Stephanie A Whetsel Borzendowski ◽  
Richard A Tyrrell
Keyword(s):  
Visual Acuity ◽  
Older Drivers ◽  
Visual Performance ◽  
High Beam ◽  
Disability Glare ◽  
Landolt C

Drivers' judgments of the magnitude of disability glare caused by high-beam headlights may not match actual declines in visual performance. This study investigated younger and older drivers' beliefs about their own visual performance in the presence of headlight glare. Eleven older drivers and seventeen younger drivers judged the distance at which they would just be able to recognize the orientation of a white Landolt C if it were present adjacent to the headlamps of a stationary opposing vehicle at night. The younger participants were generally accurate in their estimates of the recognition distance of the stimulus, while older participants significantly overestimated both their own acuity and the effect of glare on their vision. From this study, we see that older drivers' judgments about the disabling effects of oncoming headlights may be systematically inaccurate. These misperceptions about headlight glare may help explain why drivers tend to underuse high beams.

Visual Acuity at Hyperbaric Air Pressure

1976 ◽  
Vol 43 (3) ◽  
pp. 983-986 ◽  
Author(s):  
N. A. M. Schellart
Keyword(s):  
Visual Acuity ◽  
Pressure Chamber ◽  
Air Pressure ◽  
Considerable Reduction ◽  
Open Sea ◽  
Landolt C

The visual acuity of five divers in a dry pressure chamber was measured with a Landolt C test. Only one of them showed a significant reduction at 7.0 atm. These results contrast sharply with open sea experiments, which show a considerable reduction at much lower pressures (Baddeley, 1968). It is suggested that besides stresses, luminance differences, also turbidity, as a function of depth may account for the discrepancy.

scholarly journals Contrast Ratios, Colour Elements, and Polarities in Visual Acuity Measurements

2018 ◽  
Vol 7 (3.11) ◽  
pp. 89
Author(s):  
Ai Hong Chen ◽  
Nurulain Muhamad
Keyword(s):  
Visual Acuity ◽  
Contrast Ratio ◽  
Rank Test ◽  
Friedman Test ◽  
Contrast Polarity ◽  
Signed Rank ◽  
Wilcoxon Signed Rank Test ◽  
Signed Rank Test ◽  
Lower Contrast ◽  
Landolt C

This study was aimed to investigate the effects of contrast ratios, colour elements, and polarities on visual acuity measurements. The visual acuities of 18 subjects were measured using 6 different modifications of the Landolt C chart in a 4-metre LogMAR design: (M1) black-on-white [contrast ratio: 0.8]; (M2) white-on-black [contrast ratio: 0.8]; (M3) black-on-white [contrast ratio: 0.5]; (M4) yellow-on-green [contrast ratio: 0.8]; (M5) yellow-on-green [contrast ratio: 0.5]; and (M6) black-on-yellow [contrast ratio: 0.8]. Comparative analysis was performed to examine the effects of the three aforementioned parameters on visual acuity measurements. The visual acuities were found to be significantly different between the contrast ratios of 0.5 and 0.8, regardless of whether colour elements were present (black-on-white) or otherwise (yellow-on-green) [Friedman test: c2 (3) = 24.24, p < 0.05]. Interestingly, the LogMAR score was found to be significantly different between the yellow-on-green and black-on-yellow chart designs when the contrast ratio remained constant at 0.8 [Wilcoxon signed-rank test: z = 2.950, p < 0.05]. However, the effect of contrast polarity (positive/ negative) on visual acuity was not significant when the contrast ratio was fixed at 0.8 [Wilcoxon signed-rank test: z = 0.318, p > 0.05].  A lower contrast ratio and mid-range wavelength colour reduced visual acuity. The effect of contrast polarity without colour elements on visual acuity was negligible.  

Visual acuity as measured with Landolt C chart and Early Treatment of Diabetic Retinopathy Study (ETDRS) chart

2010 ◽  
Vol 249 (4) ◽  
pp. 601-605 ◽  
Author(s):  
Hsi-Kung Kuo ◽  
Ming-Tse Kuo ◽  
Ing-Soo Tiong ◽  
Pei-Chang Wu ◽  
Yung-Jen Chen ◽  
...  
Keyword(s):  
Visual Acuity ◽  
Diabetic Retinopathy ◽  
Early Treatment ◽  
Landolt C

scholarly journals Repeatability and Agreement of Visual Acuity Using the ETDRS Number Chart, Landolt C Chart, or ETDRS Alphabet Chart in Eyes With or Without Sight-Threatening Diseases

2018 ◽  
Vol 136 (3) ◽  
pp. 286 ◽  
Author(s):  
Voraporn Chaikitmongkol ◽  
Onnisa Nanegrungsunk ◽  
Direk Patikulsila ◽  
Paisan Ruamviboonsuk ◽  
Neil M. Bressler
Keyword(s):  
Visual Acuity ◽  
Landolt C

Performance Evaluation Tests for Environmental Research (PETER): Landolt C Reading Test

1980 ◽  
Vol 24 (1) ◽  
pp. 335-339 ◽  
Author(s):  
John C. Guignard ◽  
Alvah C. Bittner ◽  
Steven W. Einbender ◽  
Robert S. Kennedy
Keyword(s):  
Visual Acuity ◽  
Performance Evaluation ◽  
Fine Structure ◽  
Repeated Measures ◽  
Performance Test ◽  
Environmental Research ◽  
Future Performance ◽  
Error Measures ◽  
The Stability ◽  
Landolt C

A Landolt C visual acuity test was evaluated for inclusion in a battery of Performance Evaluation Tests for Environmental Research (PETER) for use in repeated measures experiments. Eight subjects were tested for 12 days to determine stability of means, standard deviations and cross-day correlations. Mixed results for these cross-day correlation analyses made questionable the stability of speed and error measures. Fine-structure analyses indicated that the task was more a measure of response accuracy than acuity. Fine-structure analyses in future performance test evaluation and exploration of alternative visual acuity tests are recommended. It is concluded that the Landolt C test in the form used is not stable and cannot be recommended as a test of visual acuity for inclusion in PETER.

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