Effect of optical defocus on colour perception

Daily experience shows that colour of a very distant object cannot be accurately determined. It is assumed that visual acuity (VA) loss is one of the factors at play in this case. The effects of reduced VA as a result of refractive error or optical defocus on colour vision have not been examined. Such study willdictate the need or otherwise for optical correction before assessment of colour vision. The purpose of this study therefore, was to investigate the effects of optical defocus on colour vision in individuals with normal colour vision. Twenty nine young adult subjects (11 male and 18 females) were included in this study. Their ages ranged from 11 to 29 years with a mean of 22.1 ± 3.4 years. All subjects had VA of 6/6 or better and normal colour vision. The colour vision was evaluated with the Farnsworth panel D-15 (desaturated). Each subject was optically defocused to VA of 6/24, 6/60 and 1/60(6/360) at 6 meters respectively and colour vision was assessed at each reduced VA. At VA of 6/24, colour vision was not affected in all subjects. When the VA was reduced to 6/60, however, 15 (51%) of the subjects failed the colour vision test. When the VA was further reduced to 1/60 by optical defocus, 24 (83%) of the subjects failed the colour vision test. It was concluded that optical defocus and reduced VA can adversely affect colour vision test findings. While VA reduction to 6/24 may not affect the colour vision results, VA of 6/60 can. It is therefore, recommended that in clinical colour vision testing and colour vision screening, VA should first be assessed andcompensated, especially if uncorrected VA is 6/24 or worse.

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Prototyp eines Bildschirmfarbtests

Optometry & Contact Lenses ◽

10.54352/dozv.jykr6019 ◽

2021 ◽

Vol 1 (5) ◽

pp. 172-177

Author(s):

Wolfgang Cagnolati

Keyword(s):

Colour Vision ◽

Test Material ◽

Colour Perception ◽

Vision Disorder ◽

Digital Testing ◽

Colour Scale ◽

Colour Sense ◽

Normal Colour ◽

The Difference ◽

Vision Defects

Purpose. The purpose of this study is to develop a new digital colour vision test. Material and Methods. Based on the principle of metamerism, a digital testing strategy was developed for efficient measurement of colour vision. Twentyfive subjects participated in the study, 21 of whom had normal colour vision and four of whom had a congenital colour vision disorder. Differences in colour vision were examined by monocular presentation of halfquadrants of different hues and degrees of saturation, and the algorithm calculated the colour vision defects that occurred based on the subjects’ responses. The following colour vision values were assigned from the data: a colour scale range of 2.76 – 7.18 for normal colour vision and greater than 7.18 for colour sense disorders. A second new colour scale assessed the type of colour vision disturbance: in the range of 0 – 0.3 were values for a deuteranomaly, in the range of 0.6 – 1.0 were values for a protanomaly, and a value of 1.0 corresponded to a tritanomaly. Results. The difference in colour vision between subjects with normal colour vision and those with a colour vision defect was confirmed (p < 0.001) by measuring the type and the extent of the colour vision disorder was determined. In the group of subjects with normal colour perception, a mean colour scale value of 3.41 ± 0.52 was determined. The extent of colour sense disturbance for the subjects with colour vision impairment was values of 7.18 – 14.33 according to the colour scale, indicating greater variability. Conclusion. The developed algorithm provided meaningful results regarding the colour perception of the test persons. It was possible to differentiate between normal colour vision and colour vision disorder could be shown. Furthermore, the variation between subjects with normal colour vision could be evaluated. Keywords. Colors, colour vision, colour sense disorders, colour test, software algorithm

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Automated vision screening of children using a mobile graphic device

Eye ◽

10.1038/s41433-021-01862-x ◽

2021 ◽

Author(s):

Steven A. Kane ◽

Mark Gaspich ◽

Julia Kane ◽

Sarah A. Weitzman ◽

Albert Hofeldt

Keyword(s):

Visual Acuity ◽

Mobile Device ◽

Colour Vision ◽

Specific Method ◽

Vision Screening ◽

Limits Of Agreement ◽

Graphic Device ◽

Range Testing ◽

The Mean ◽

Image Pairs

Abstract Background/Objective Can measuring interocular brightness disparity, acuity, and colour vision classify children with amblyopia? Subjects/Methods Two hundred eight subjects (3–14 years) were recruited for a prospective, observational protocol to measure interocular brightness disparity, uniocular acuities with and without a pinhole, and colour vision using an iPad. Subjects looked through polarizing filters and chose the brighter of two spaceships to measure interocular brightness disparity. The differential brightness of image pairs was varied through a staircase algorithm until equal brightness was perceived. Acuities and colour vision were tested with tumbling Es and AO-HRR colour plates, respectively. Unilateral amblyopia was later confirmed in two subjects. Results Binocular brightness balance on the iPad detected amblyopes with 100% sensitivity and specificity. Using 20/30 as cutoff for normal acuity, 1 of the amblyopes was detected, and non-amblyopes were excluded by visual acuity pinhole testing. The mean difference between iPad and E-Chart visual acuities with pinhole was 0.02 logMAR with limits of agreement from −0.08 to +0.11 logMAR. iPad and printed plates Colour vision testing produced identical results. Testing times were brief and exit pleasure responses were positive. Mean and range testing times for Brightness Sense, Colour vision, and Visual Acuity were 32.7 s (range = 12–63 s), 52.8 min (range = 17–95 s), and 88.75 s (range = 41–188 s), respectively. Conclusions Interocular brightness disparity, acuity, and colour vision can be measured in children as young as 3 years old solely through playing a game on a mobile device. Interocular brightness disparity is a sensitive and specific method to detect unilateral amblyopia.

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Comparison of contrast sensitivity in myopic patients using spectacle and contact lens correction

10.53350/pjmhs21155951 ◽

2021 ◽

Vol 15 (5) ◽

pp. 951-953

Author(s):

Sadaf Qayyum ◽

Zubair Wahab ◽

Rabia Saeed ◽

Anbar Zulfiqar ◽

Ayisha Shakeel ◽

...

Keyword(s):

Visual Acuity ◽

Contrast Sensitivity ◽

Contact Lens ◽

Contact Lenses ◽

Cross Sectional Study ◽

Cross Sectional ◽

Spectacle Lens ◽

Optical Correction ◽

Eye Examination ◽

Optical Defocus

Aim: To compare the contrast sensitivity in different categories of myopia using two different optical correction spectacles and contact lens correction. Methods: This cross-sectional study in design was conducted from August 2018 to May 2019 at the Ophthalmology Department of Madinah Teaching Hospital Faisalabad.45 subjects corrected with spectacles lenses and contact lenses all had corrected visual acuity of 6/9 or better were studied.The extent of myopia determined the three groups. All individuals were subjected to spectacles and Contact lens correction using slitlamp for anterior eye examination and for the fundus examination. The assessment of visual acuity was carried out by the Snellen vision Chart at 6m distance and contrastssensitivity was tested by Pelli- Robson chart. Results: Results showed a significant relationship between contrast sensitivity and type of optical correction. There were significant results of the independent t-test for spectacle and contact lenses 0.00 (p<0.005). However, the mean contrast sensitivity was better for all the three groupswith contact lens correction as compared to spectacle lens correction.Contact lenses provide better contrast sensitivity than spectacle lenses. Conclusion: Comparison between contact lens and spectacle correction was done and better quality contact lenses reduce optical defocus and give better results of contrast sensitivity. Results also concluded that loss of contrast sensitivity will be interpreted as early loss of retinal functions in severe myopes. Keywords: Myopia, Contrast sensitivity, Spectacle lens, Contact lens

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An Ishihara-style test of animal colour vision

10.1101/382051 ◽

2018 ◽

Author(s):

Karen L. Cheney ◽

Naomi F. Green ◽

Alexander P. Vibert ◽

Misha Vorobyev ◽

N. Justin Marshall ◽

...

Keyword(s):

Colour Vision ◽

Weber Fraction ◽

List Type ◽

Colour Perception ◽

Sensory Bias ◽

Long Wavelength ◽

Single Target ◽

Normal Colour ◽

Behavioural Tests ◽

Colour Signals

AbstractColour vision mediates ecologically relevant tasks for many animals, such as mate choice, foraging and predator avoidance. However, our understanding of animal colour perception is largely derived from human psychophysics, even though animal visual systems differ from our own. Behavioural tests of non-human animals are required to understand how colour signals are perceived by them.Here we introduce a novel test of colour vision in animals inspired by the Ishihara colour charts, which are widely used to identify human colour deficiencies. These charts consist of dots that vary in colour, brightness and size, and are designed so that a numeral or letter is distinguishable from distractor dots for humans with normal colour vision. In our method, distractor dots have a fixed chromaticity (hue and saturation) but vary in luminance. Animals can be trained to find single target dots that differ from distractor dots in chromaticity. We provide Matlab code for creating these stimuli, which can be modified for use with different animals.We demonstrate the success of this method with triggerfìsh, Rhinecanthus aculeatus, and highlight behavioural parameters that can be measured, including success of finding the target dot, time to detect dot and error rate. Triggerfìsh quickly learnt to select target dots that differed from distractors dots regardless of the particular hue or saturation, and proved to use acute colour vision. We measured discrimination thresholds by testing the detection of target colours that were of increasing colour distances (ΔS) from distractor dots in different directions of colour space. At least for some colours, thresholds indicated better discrimination than expected from the Receptor Noise Limited (RNL) model assuming 5% Weber fraction for the long-wavelength cone.This methodology seems to be highly effective because it resembles natural foraging behavior for the triggerfìsh and may well be adaptable to a range of other animals, including mammals, birds, bees and freshwater fish. Other questions may be addressed using this methodology, including luminance thresholds, sensory bias, effects of sensory noise in detection tasks, colour categorization and saliency.

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Visual Acuity in Myopes with Standard and Reversed Contrast Optotypes

Proceedings of the Latvian Academy of Sciences Section B Natural Exact and Applied Sciences ◽

10.1515/prolas-2017-0004 ◽

2017 ◽

Vol 71 (1-2) ◽

pp. 22-26

Author(s):

Gatis Ikaunieks ◽

Anete Petrova ◽

Karola Panke ◽

Gunta Krūmiņa

Keyword(s):

Visual Acuity ◽

Contact Lens ◽

Contact Lenses ◽

Optical Correction ◽

Optical Defocus ◽

Spectacle Correction ◽

Low Order

Abstract The aim of this study was to assess the visual acuity of myopes with standard and reversed contrast optotypes and to determine how the visual acuity of myopes is affected by optical defocus and the type of optical correction, either contact lenses or spectacles. Twenty-three myopic subjects (18 and 23 years old) with uncorrected vision had their visual acuity assessed with both standard and reversed contrast optotypes. The study also included 10 myopes with contact lens as well as habitual spectacle correction. The visual acuity for myopes with uncorrected vision was better with reversed than standard contrast optotypes. Better reversed contrast than standard contrast visual acuity was obtained also with spectacle and contact lens correction. This result could be due in part to low order aberrations (optical defocus) in myopes spectacle or contact lenses correction.

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VII.—A New Method of investigating Colour Blindness, with a Description of Twenty-three Cases

Proceedings of the Royal Society of Edinburgh ◽

10.1017/s0370164600023853 ◽

1923 ◽

Vol 42 ◽

pp. 75-88 ◽

Cited By ~ 1

Author(s):

R. A. Houstoum

Keyword(s):

Colour Vision ◽

Extreme Case ◽

Original Method ◽

Colour Perception ◽

Homogeneous Population ◽

Normal Colour ◽

The Subject ◽

Colour Blindness ◽

Trained Observers ◽

The University

During the past four years I have been conducting surveys of the colour vision of students in the University of Glasgow. The first survey was made by a colour-perception spectrometer very similar to Dr Edridge-Green's instrument, and embraced 79 observers. The second survey was made by Dr Edridge-Green's bead test, and embraced 100 observers. The third survey, carried out in collaboration with Miss Margaret A. Dunlop, was made by an original method, called here for short the microscope test, and embraced 1000 observers. At present there are two other surveys under progress. The object of these surveys is to find a numerical method of specifying goodness of colour vision; to see, by the application of statistical methods, whether the colour blind fall naturally into groups or are merely outliers of a homogeneous population; to find whether colour blindness is a Mendelian characteristic for men and merely an extreme case of normal variation for women; and to throw light on the subject of colour vision generally. Consequently, the normal have been investigated with as much care as the colour blind. But in the course of the four years I have made the acquaintance of many trained observers with abnormal colour vision, and have been possessed with an ever-growing desire to know exactly, irrespective of all theory, what was the matter with their colour vision. In spite of the vast literature on the subject, the tests generally have been of a very superficial nature, and unsatisfactory to the man with mathematical instincts. As these abnormal cases were beginning to leave the University, I addressed myself last spring to the problem of finding a method of testing which would describe their condition independent of theory, and, indeed, independent of words. This paper describes how the problem was solved, and gives data for twenty-three cases of colour blindness, four of normal colour vision, and one case of exceptionally good colour vision.

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

Dubai Medical Journal ◽

10.1159/000512521 ◽

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

Introduction: 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 <6/18 to 3/60 or having visual field loss to <20° in the better-seeing eye. Children defined to have “blindness” have presenting vision of <3/60 or corresponding visual field of <10°. Purpose: 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. Methods: 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. Results: 1,591 students were screened and evaluated from the end of 2016 to mid-2017. About 21.37% (n = 340) had impaired vision with 20.9% (n = 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. Conclusion: A significant number of students were detected to have uncorrected refractive errors among the vision impaired group (59%, n = 197) despite a school-based vision screening program in place. Seventy-eight percent of the amblyopia cases (n = 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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Possibilities of scleral lenses for visual rehabilitation of patients with corneal scars

Modern technologies in ophtalmology ◽

10.25276/2312-4911-2021-5-157-161 ◽

2021 ◽

pp. 157-161

Author(s):

O.I. Ryabenko ◽

◽

O.M. Selina ◽

E.M. Tananakina ◽

◽

...

Keyword(s):

Visual Acuity ◽

Contact Lenses ◽

Efficacy And Safety ◽

Visual Rehabilitation ◽

Optical Correction ◽

Vision Correction ◽

Post Traumatic ◽

Key Words Cornea ◽

Irregular Astigmatism ◽

Spectacle Correction

Purpose. To analyze the efficacy and safety of SCL in patients with corneal cicatricial changes and other concomitant conditions. Material and мethods. The study included 19 patients (20 eyes) with cicatricial deformity of the cornea of various etiology, who were fitted with scleral contact lenses. Results and discussions. The use of SCL is possible in post-traumatic pathology, such as corneoscleral scars with or without aphakia, as well as after keratitis with an outcome in cicatricial deformity, cicatricial changes after a burn. A significant increase in visual acuity compared with spectacle correction has been proven. Depending on the topography of the scar, it is possible to select scleral lenses such as Oblate and Prolate, as well as with different versions of the support zone: both toric and quadratic. Conclusion. Scleral lenses can be successfully used for optical correction in patients with cicatricial changes in the cornea and other concomitant post-traumatic conditions of ineffectiveness of other methods of visual rehabilitation. Key words: cornea, lenses, vision correction, contact lenses, visual rehabilitation, scleral lenses, corneal scars, post-traumatic astigmatism, aphakia, keratitis, toric lenses, quadratic lenses, astigmatism, irregular cornea, regular cornea, regular astigmatism, irregular cornea, irregular astigmatism, prolate, oblate.

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Modelling the effects of inter-observer variation on colour rendition

Lighting Research and Technology ◽

10.1177/1477153517744387 ◽

2017 ◽

Vol 51 (1) ◽

pp. 37-54 ◽

Cited By ~ 2

Author(s):

MJ Murdoch ◽

MD Fairchild

Keyword(s):

Colour Vision ◽

Spectral Characteristics ◽

Observer Variation ◽

Light Sources ◽

Standard Observer ◽

Natural Range ◽

Normal Colour ◽

Range Of Variation

The colour rendition characteristics of light sources are quantified with measures based on CIE standard observers, which are reasonable representations of population averages. However, even among people with normal colour vision, the natural range of variation in colour sensitivity means any individual may see something different than the standard observer. Modelling results quantify the effects of these inter-observer differences on colour rendition measures defined by IES TM-30-15. In general, inter-observer differences tend to be smaller for light sources with high colour fidelity values, and they are affected by spectral characteristics of different lighting technologies. The magnitude of variation in colour rendition measures, up to 5–10 units in IES TM-30-15 ( Rf, Rg), measures is compared with other sources of variability and ambiguity.

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Visual rehabilitation of patients with irregular cornea

The Eye ◽

10.33791/2222-4408-2019-1-26-32 ◽

2019 ◽

Vol 125 (2019-1) ◽

pp. 26-32 ◽

Cited By ~ 1

Author(s):

Alexander Myagkov ◽

Elena Belousova ◽

Natalya Ignatova ◽

Oksana Petrova

Keyword(s):

Visual Acuity ◽

Contact Lenses ◽

Visual Comfort ◽

Irregular Surface ◽

Visual Rehabilitation ◽

Main Method ◽

Landing Zone ◽

Optical Correction ◽

Selection Of ◽

Spectacle Correction

Purpose: To estimate the possibility of optical correction of an irregular surface of a cornea at primary ectasia (keratoconus) and secondary ectasia (a consequence of radial keratotomy (RKT) and Keratoplasty) for improvement of the maximum of visual acuity. Material and methods: In the study the scleral gas-permeable lenses (SGCL) were fitting by the 60 patients, it was 45 men and 15 women from them. The 46 patients had various stage of keratoconus and 14 patients had the keratectasia after RKT. On the 5 eyes of the patients was carried out keratoplasty earlier. Criteria of successful selection of SGCL considered achievement of steadily high visual acuity, comfort of carrying and the optimal clearance in apical zone, in the limbal and landing zone on the conjunctiva also. The results: In the course of the study, the maximum visual acuity in all patients was achieved with mini-SGKL correction irrespective of type of keratoektasia. All patients observed visual comfort compared with spectacle correction or correction with other types of contact lenses. Conclusion: Scleral gas-permeable contact lenses are the main method of correction at patients with irregular corneas and provide the best visual acuity.

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