scholarly journals Human Gaze Following Response Is Affected by Visual Acuity

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Marcella Spoor ◽  
Behdokht Hosseini ◽  
Bart van Alphen ◽  
Maarten A. Frens ◽  
Jos N. van der Geest
Keyword(s):  
Visual Acuity ◽  
Spatial Frequency ◽  
Luminance Contrast ◽  
Gaze Following ◽  
Refractive Errors ◽  
Good Visual Acuity ◽  
Spatial Frequencies ◽  
Moving Stimulus ◽  
Refractive Correction ◽  
Landolt C

The present study investigated how gaze following eye movements are affected by stimulus contrast and spatial frequency and by aberrations in central visual acuity due to refractive errors. We measured 30 healthy subjects with a range of visual acuities but without any refractive correction. Visual acuity was tested using a Landolt-C chart. Subjects were divided into three groups with low, intermediate, or good visual acuity. Gaze following responses (GFR) to moving Gabor patches were recorded by video-oculography. In each trial, the subjects were presented with a single Gabor patch with a specific spatial frequency and luminance contrast that moved sinusoidally in the horizontal plane. We observed that GFR gain decreased with increasing spatial frequency and decreasing contrast and was correlated with visual acuity. GFR gain was lower and decreased more for subjects with lower visual acuity; this was especially so for lower stimulus contrasts that are not tested in standard acuity tests. The largest differences between the groups were observed at spatial frequencies around 4 cpd and at contrasts up to 10%. Aberrations in central visual acuity due to refractive errors affect the GFR response depending on the contrast and spatial frequency of the moving stimulus. Measuring this effect may contribute to a better estimate of changes in visual function as a result of aging, disease, or treatments meant to improve vision.

scholarly journals High Visibility Conditions in a Sunset Environment

2021 ◽  
Vol 11 (16) ◽  
pp. 7229
Author(s):  
Tatsuya Iizuka ◽  
Takushi Kawamorita ◽  
Choku Takenaka ◽  
Hajime Tsuji ◽  
Hiroyuki Kanai ◽  
...  
Keyword(s):  
Visual Acuity ◽  
Spatial Frequency ◽  
Visual Target ◽  
Color Pattern ◽  
Refractive Errors ◽  
Stripe Pattern ◽  
Spatial Frequencies ◽  
Set Up ◽  
Healthy Participants ◽  
Dark Room

There is no standard for high-visibility safety clothing for general pedestrians, nor is it widely used. Therefore, this study investigated visibility in order to examine the standards for high-visibility safety clothing for general pedestrians. Methods: Twenty healthy participants (mean age, 22.4 ± 4.4 years) without ocular disease, except for refractive errors, were studied. All participants had healthy visual acuity in corrected vision. This study assumed sunset conditions in Japan. The light source was set up in a dark room, and the illuminance in front of the visual target was set to 300 lx. We investigated the visibility of 142 patterns of black and yellow combination samples with different spatial frequencies, pattern types, angles, and color ratios. Results: The highest visibility was found at 5.0 cycles per degree of the stripe pattern at the spatial frequency, yellow ratio of 75%, and a stripe angle of 165°. Conclusions: Under sunset conditions, the brightness decreased when black was combined with yellow. However, it forms a two-color pattern and becomes more conspicuous. The highest visibility was obtained by arranging black and yellow in a diagonal stripe pattern. We predict that establishing clothing standards based on the results of this study will help design safety clothing with increased visibility.

scholarly journals High Visibility Conditions in a Sunset Environment

2021 ◽  
Author(s):  
Tatsuya Iizuka ◽  
Takushi Kawamorita ◽  
Choku Takenaka ◽  
Hajime Tsuji ◽  
Hiroyuki Kanai ◽  
...  
Keyword(s):  
Visual Acuity ◽  
Spatial Frequency ◽  
Visual Target ◽  
Color Pattern ◽  
Refractive Errors ◽  
Stripe Pattern ◽  
Normal Visual Acuity ◽  
Spatial Frequencies ◽  
Set Up ◽  
Dark Room

Abstract Purpose: There is no standard for high-visibility safety clothing for general pedestrians, nor is it widely used. Therefore, this study investigated visibility in order to examine the standards for high-visibility safety clothing for general pedestrians. Methods: Twenty normal participants (mean age, 22.4 ± 4.4 years) without ocular disease, except for refractive errors, were studied. All participants had normal visual acuity in corrected vision. This study assumed sunset conditions in Japan. The light source was set up in a dark room, and the illuminance in front of the visual target was set to 300 lx. We investigated the visibility of 142 patterns of black and yellow combination samples with different spatial frequencies, pattern types, angles, and color ratios. Results: The highest visibility was found at 5.0 cycles per degree of the stripe pattern at the spatial frequency, yellow ratio of 75%, and a stripe angle of 165°. Conclusions: Under sunset conditions, the brightness decreased when black was combined with yellow. However, it forms a two-color pattern and becomes more conspicuous. The highest visibility was obtained by arranging black and yellow in a diagonal stripe pattern. We predict that establishing clothing standards based on the results of this study will help design safety clothing with increased visibility.

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 Effectiveness of refractive error correction for people with oculocutaneous albinism in Nepal

2017 ◽  
Vol 8 (6) ◽  
pp. 30-34 ◽  
Author(s):  
Arjun M Bhari ◽  
Kabindra Bajracharya ◽  
Hari B Thapa ◽  
Maria Gautam ◽  
Araniko Pandey ◽  
...  
Keyword(s):  
Visual Acuity ◽  
Error Correction ◽  
Oculocutaneous Albinism ◽  
Outreach Program ◽  
Refractive Errors ◽  
Medical Sciences ◽  
Telephone Contact ◽  
Refractive Correction ◽  
And Function ◽  
Objective Improvement

Background: Albinism is commonly associated with high refractive errors, but some clinicians are reluctant to prescribe glasses because reduced vision persists due to additional non-refractive visual problems.Aims and Objective: The purpose of this study was to evaluate the effectiveness of glasses in people with oculocutaneous albinism in Nepal.Materials and Methods: People with Oculocutaneous albinism (OCA) were prospectively examined through an outreach program of Lumbini Eye Institute, Nepal. Glasses were prescribed to determine the objective improvement in visual acuity (VA) and strabismus. Compliance with spectacles wear was assessed by telephone contact after 3 weeks and categorized as excellent: >75% of awake hours; good: 50–75% of awake hours; fair: 26–50% of awake hours and poor: <25%.Results: Thirty one people (65% male) mean age 18 years (range: 3 to 50) with OCA were examined. Mean refractive correction was –0.40±4.3 diopters spherical equivalents (range: −11.0 to +7.0 D). Mean visual acuity at distance was 0.9±0.28(6/50) corrected and 1.150.31(5/60) uncorrected (P = 0.000) in 62 eyes. Mean neat VA was1.74±0.89M corrected and 2.06±1.20M uncorrected (P = 0.004). Forty eight per cent (15 people) had fusion with or without glasses and one had fusion only with glasses. Compliance was excellent in 52% (16), fair in 26% (8), good in 12% (4), and poor in 10% (3).Conclusion: Providing eye glasses resulted in a clinically and functionally significant improvement in visual acuity and function in people with OCA.Asian Journal of Medical Sciences Vol.8(6) 2017 30-34

Visual Acuity of the Aging Hyperopic Eye in the Intermediate Range

1977 ◽  
Vol 21 (3) ◽  
pp. 184-187
Author(s):  
Paul G. Rasmussen ◽  
Kenneth W. Welsh ◽  
John A. Vaughan
Keyword(s):  
Visual Acuity ◽  
Refractive Errors ◽  
Intermediate Range ◽  
Good Visual Acuity ◽  
Convex Lens ◽  
Normal Reading ◽  
Functional Visual Acuity ◽  
Visual Range

Corrective lenses are normally prescribed to correct the refractive errors of the eyes to give good visual acuity at distance (6 m). When presbyopia is present, a convex lens addition (bifocal power) may be included as part of the near correction to move the near focussing point back into the normal reading range (36 to 46 cm). The advantages gained by these corrections may be minimal, or even detrimental, to visual acuity at the intermediate range. A study was undertaken to determine the functional visual acuity of presbyopic individuals at the intermediate visual range with and without the best near and best distant vision corrections.

scholarly journals Are Contrast Sensitivity Functions Impaired in Insulin Dependent Diabetics Without Diabetic Retinopathy?

1999 ◽  
Vol 42 (4) ◽  
pp. 133-138 ◽  
Author(s):  
Vladimír Liška ◽  
Miroslav Dostálek
Keyword(s):  
Visual Acuity ◽  
Diabetic Retinopathy ◽  
Spatial Frequency ◽  
Contrast Sensitivity ◽  
Dependent Diabetes Mellitus ◽  
Control Group ◽  
Study Group ◽  
Sensitivity Functions ◽  
Spatial Frequencies ◽  
Insulin Dependent

Purpose: To confirm the influence of multilevel metabolic disturbance of insulin dependent diabetes mellitus (IDDM) on the vision even before the onset of the other changes routinely evaluated by ophthalmologists. Methods: Contrast sensitivity functions (CSFs) were estimated using the VCTS 6500 board. The standardised measurement procedure was performed. The value of the threshold contrast sensitivity was obtained for five spatial frequencies (1.5 - 3 - 6 - 12 - 18 c/deg). Other data was collected (duration of diabetes, BCVA, funduscopy, fluoresceine angiography, HbA1C). The study group consisted of 48 IDDM patients (94 eyes) without diabetic retinopathy and with Snellen BCVA > 1.0. The control group (56 normals, 98 eyes) was age and BCVA matched. Results: Highly statistically significant decrease of the CSFs in all spatial frequencies in the study group was obtained. Correlation between duration of the diabetes and impaired degree of CSFs was present in the middle spatial frequency. No significant changes in CSFs were found among patients with pathological value of glycated hemoglobin HbA1c (>7.8 %). Conclusions: If compared with routinely used Snellen visual acuity, the CSFs are more complex descriptors of the subjects vision abilities. IDDM has an influence on these sensitive functions, especially during examination in the middle spatial frequency of 6 and 12 c/deg, before disturbing visual acuity and before changes in the retinal morphology. Decrease of CSFs was influenced mainly by the patients’ age and partially (in the middle spatial frequency) by the IDDM duration.

Responses to sinusoidal gratings of two types of very nonlinear retinal ganglion cells of cat

1989 ◽  
Vol 3 (3) ◽  
pp. 213-223 ◽  
Author(s):  
J. B. Troy ◽  
G. Einstein ◽  
R. P. Schuurmans ◽  
J. G. Robson ◽  
Ch. Enroth-Cugell
Keyword(s):  
Spatial Frequency ◽  
Ganglion Cells ◽  
Cell Model ◽  
Second Harmonic ◽  
Temporal Frequency ◽  
Receptive Fields ◽  
Cell Types ◽  
Luminance Contrast ◽  
Spatial Frequencies ◽  
Low Pass

AbstractPerhaps 35% of all of the ganglion cells of the cat do not have classical center-surround organized receptive fields. This paper describes, quantitatively, the responses of two such cell types to stimulation with sinusoidal luminance gratings, whose spatial frequency, mean luminance, contrast, and temporal frequency were varied independently. The patterns were well-focused on the retina of the anesthetized and paralyzed cat. In one type of cell, the maintained discharge was depressed or completely suppressed when a contrast pattern was imaged onto the receptive field (suppressed-by-contrast cell). In the other type of cell, the introduction of a pattern elicited a burst of spikes (impressed-by-contrast cell).When stimulated with drifting gratings, the cell's mean rate of discharge was reduced (suppressed-by-contrast cell) or elevated (impressed-by-contrast cell) over a limited band of spatial frequencies. There was no significant modulated component of response. The reduction in mean rate of suppressed-by-contrast cells caused by drifting gratings had a monotonic dependence on contrast, a relatively low-pass temporal-frequency characteristic and was greater under photopic than mesopic illuminance. If gratings of spatial frequency, that when drifted evoked a response from these cells, were instead held stationary and contrast-reversed, the mean rate of a suppressed-by-contrast cell was also reduced and that of an impressed-by-contrast cell increased. But, for contrast-reversed gratings, the discharge contained substantial modulation at even harmonic frequencies, the largest being the second harmonic. The amplitude of this second harmonic did not depend on the spatial phase of the grating, and its dependence on spatial frequency, at least for suppressed-by-contrast cells, was similar to that of the reduction in mean rate of discharge. Our results suggest that the receptive fields of suppressed-by-contrast and impressed-by-contrast cells can be modeled with the general form of the nonlinear subunit components of Hochstein and Shapley's (1976) Y cell model.

CLINICAL CHARACTERISTICS AND RESULTS OF CATARACT SURGERY IN THE SMALL PUPIL EYE BY PHACOEMUSIFICATION

2018 ◽  
pp. 79-82
Author(s):  
Van Minh Pham ◽  
Van Nam Phan ◽  
Thi Thu Nguyen
Keyword(s):  
Visual Acuity ◽  
Cataract Surgery ◽  
Clinical Characteristics ◽  
Low Vision ◽  
Sample Selection ◽  
Posterior Chamber ◽  
Good Visual Acuity ◽  
Before And After ◽  
Grade Ii ◽  
Small Pupil

Objectives: To investigate the clinical characteristics of cataract patients with small pupils and to evaluate the result of cataract surgery on the eye have small pupils by phacotechnique. Subjects and methods: Descriptive study, prospective, uncontrolled interventions. Sample selection. The sample size of 70 patients with 70 eyes of cataracts with small pupils was treated by phaco technique and intraocular lens implant within posterior chamber. Follow up to 3 months. Results: 70 eyes, the percentage of men and women was not different from 54.2% (38 male) compared to 45.8% (32 female). The mean age was 80 ± 8.74, from 58 to 99 years. The disease was mainly found in the age group over 70 years old with over 80% (51.5%). Visual acuity before surgery was very poor under 3m CF (count finger) for 68.6% (48/70). Visual acuity over 1/10 was only a small amount with 2.8% (2 eyes). Pseudoexfoliation was the most common reason complications of mydriasis with 32/70 eyes (45.7%) and 22/70 eyes (31.4%) for age. The preoperative pupilarysizewas mostly small with 63/70 eyes (90.0%), non-dilated pupils (7/70 eyes) (10.0%). Average pupil size was 3.34 mm (2 - 4mm). Iris condition: iris atrophy 20/10 eyes (28.6%), iris synechiae 11/10 (15.7%), irregular iris muscle with 51, 4% and good iris muscle accounted for 48.6%. Grade of cataract: Grade III: 31/70 eyes (44.3%), Grade IV: 32/70 eyes (45.7%), Grade II: 5/70 eyes (7.1%) and V:2/70 eyes (2.9%). Pupil expander technique: OVD injection with 42/70 eyes (60%), using iris hook with 23/70 eyes (32.9%). Pupillary size before and after intervention has changed from 3.7mm to 4.48mm. Conclusions: Iris expander techniques have been shown to have good dilated pupils: 60.0% OVD injection, iris hook was 32.9%, other methods 7.1% One-week visibility of good visual acuity was higher than that of postoperative one day (12.2%) and increased at 1 month and 3 months (20.0%). Very good visual acuity was not available and low vision group was 1.4% after 3 months. Key words: cataract surgery; phacoemusification, small pupil

scholarly journals Epidemiological Findings of Refractive Errors and Amblyopia among the Schoolchildren in Hatta Region of the United Arab Emirates

2021 ◽  
pp. 1-7
Author(s):  
Salam Chettian Kandi ◽  
Hayat Ahmad Khan
Keyword(s):  
Visual Acuity ◽  
Visual Field ◽  
United Arab Emirates ◽  
Refractive Error ◽  
Screening Program ◽  
Low Vision ◽  
Refractive Errors ◽  
Vision Screening ◽  
Screening Programs ◽  
School Based

<b><i>Introduction:</i></b> Uncorrected refractive errors and amblyopia pose a major problem affecting schoolchildren. We had previously observed that many schoolchildren in the Hatta region presented to the ophthalmology clinic with uncorrected refractive errors and amblyopia, which led us to undertake this research. As per the WHO, the term “visual impairment” can be “low vision” or “blindness.” Based on the presenting vision, “low vision” is defined for children who have vision of &#x3c;6/18 to 3/60 or having visual field loss to &#x3c;20° in the better-seeing eye. Children defined to have “blindness” have presenting vision of &#x3c;3/60 or corresponding visual field of &#x3c;10°. <b><i>Purpose:</i></b> To estimate the magnitude of uncorrected refractive errors and amblyopia among the schoolchildren aged 6–19 years and to assess the efficacy of school-based refractive error screening programs in the Hatta region of the United Arab Emirates. <b><i>Methods:</i></b> An epidemiological, cross-sectional, descriptive study was conducted on the entire student population studying in the government schools of the region. Those who failed the Snellen visual acuity chart test and those who were wearing spectacles were evaluated comprehensively by the researcher in the Department of Ophthalmology of the Hatta Hospital. Data were entered in the Refractive Error Study in School Children (RESC) eye examination form recommended by the WHO, and were later transferred to Excel sheets and analyzed by SPSS. <b><i>Results:</i></b> 1,591 students were screened and evaluated from the end of 2016 to mid-2017. About 21.37% (<i>n</i> = 340) had impaired vision with 20.9% (<i>n</i> = 333) refractive errors, of which 58% were uncorrected. Among the refractive error group, 19% (64 subjects) had amblyopia (4% of total students). The incidence of low vision was 9.5% and blindness was 0.38%. Low vision was found to be 9.5% and blindness 0.38%, taking in to account presenting visual acuity rather than best-corrected visual acuity for defining low vision and blindness. <b><i>Conclusion:</i></b> A significant number of students were detected to have uncorrected refractive errors among the vision impaired group (59%, <i>n</i> = 197) despite a school-based vision screening program in place. Seventy-eight percent of the amblyopia cases (<i>n</i> = 50) were found to be in the 11–19 years age group. Noncompliance with optical corrections was the reason for the high number of cases. A rigorous vision screening program and refractive services, complimented with awareness among parents and teachers, are recommended.

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