Blue Yellow Research Articles

Color vision of people with headaches

The aim of the study is to obtain new data on possible changes in color vision of people with headaches. The object of the study is people who periodically experience primary headaches of different nature. The subject of the study is the specificity of perception of chromatic parameters of the environment and color sensitivity of people with headaches of different nature, quality, intensity and frequency. The data were collected using the Farnsworth-Munsell standard clinical color vision test (FM-100). The study involved 65 people aged 17 to 66 years. The results of the assessment of color vision in the experimental group were compared with the normative indicators and data obtained in the age-matched control group (N=40). Special attention was paid to discussing the possible causes of the identified disorders and analyzing the correlation between various aspects of headache with individual indicators of color sensitivity. The data analysis included calculating the total error (TES), as well as partial errors (PES) along the blue-yellow (B-Y) and red-green (R-G) axes. We also identified partial errors for individual tones. The study revealed a noticeable specificity in the perception of blue-green and blue shades of patients with severe, chronic and non-localized headaches. Since the detected color vision disorders appear to be temporary and are most likely typical of the premonitory phase of headaches, the results of this study may contribute to understanding of headache predictors. Since the identified changes relate to only one group of (blue) shades, the findings of the study can be used in the development of alternative treatment methods. In particular, in choosing the optimal color of tinted lenses, which are offered to patients to relieve headaches and reduce their frequency.

Effect of macular pigment optical density on Yellow‐Blue and Red‐Green colour discrimination

The macular pigment (MP) absorbs preferentially short‐wavelength light and its narrow spectral absorption curve overlaps mostly the spectral responsivity function of S‐cones, although the M‐ and L‐cones are also affected. The MP is restricted to the centre ~14° disc region of the retina with a peak optical density (OD) at the centre in the range 0 to 1 log units. Although the macular pigment optical density (MPOD) decreases rapidly with increasing eccentricity, carotenoid supplementation studies reveal a large uptake of lutein and zeaxanthin, particularly in the parafoveal region and covering the centre ~6° to 8° of the fovea (doi: 10.1111/j.1475‐1313.2006.00386.x).Since the MP contributes to the reduced excitation of S‐cones, it is of interest to examine the effects MP may have on colour vision, particularly when ‘blue‐blocking’ lenses are also involved. We studied the relationship between MPOD and red/green (RG) and yellow/blue (YB) colour thresholds by measuring the spatial distribution of the MP in normal trichromats using the Macular Assessment Profile (MAP) test (doi: 10.1111/j.1475‐1313.2010.00748.x) and the corresponding RG and YB colour thresholds using the CAD test (doi:10.1093/bmb/ldx007).The results show negligible correlation between peak MPOD and YB thresholds and a small, but significant negative correlation with RG thresholds. This observation is of interest since increased MPOD values result in lower RG thresholds. The same experiment was also carried out in subjects with significantly larger amounts of MP following 3 months of supplementation with carotenoids. When averaged over the centre disc region of 2.5° and then over a parafoveal annulus between 2.5° and 4°, the corresponding, mean MP densities show only negligible correlations with RG and YB colour thresholds. To explain these findings, we calculated the expected cone‐contrasts for S‐, M‐ and L‐cones for chromatic displacements defined by the threshold ellipse. The results show that MP absorption of short‐wavelength light has a negligible effect on S‐cone contrast over the whole range of displacement directions associated with the colour threshold ellipse. Repeated calculations with simulated MPOD values up to 1 log unit, produced the same result. More recently, we modelled the effects ‘blue‐blocking’ lenses and pre‐receptor filters in the eye to explore changes to the orientation and the size of the colour threshold ellipse. The model predicts well the measured RG and YB thresholds and confirms the absence of significant threshold changes for MPOD values in the range 0 to 1 log unit. The model does, however, predict systematic changes in the orientation of the major axis (i.e., the tritan axis) and MPOD. These observations are of interest since the orientation of the major axis of the best‐fit ellipse appears to decrease monotonically from ~75° to 55°, as MPOD increases from very small values up to a peak OD of 1 log unit. More work is needed to investigate how YB and RG chromatic sensitivity is affected by combined absorption of short‐wavelength light by MPOD, the lens of the eye and ‘blue‐blocking’ spectacle lenses.

Effect of pre‐receptor filters on chromatic sensitivity and other visual functions in the eye

Spatial and spectral information carried by light emitted from visual displays is filtered as it passes through spectacle lenses in front of the eye as well as by filters within the eye. The image forming and the spectral transmittance properties of the elements involved in image formation in the eye cause changes in both the luminance and colour contrast in retinal images. In addition, the amount of light that reaches the retina is always reduced by pre‐receptor filters and this reduction in retinal illuminance can cause diminished retinal sensitivity to both luminance and colour contrast. Of particular interest are the use of coloured lenses in front of the eye to reduce the short‐wavelength content of the light that reaches the retina and the use of ‘notch’ filters to absorb light selectively in certain wavebands, with inevitable consequences on both the luminance and chromatic contrast of retinal images. The presence of variant cone‐pigments in some subjects or the complete absence of one class of cone pigment in others, can also produce large deviations in both luminance and colour contrast signals that can either enhance or diminish the conspicuity of coloured objects (doi: 10.1364/josaa.22.000017).The purpose of this study was to develop and validate a model of red/green (RG) and yellow/blue (YB) colour discrimination that can also predict how chromatic sensitivity is affected by the use of spectrally‐selective, spectacle lenses or by filters internal to the eye, when viewing visual displays. We examined how RG and YB colour thresholds relate to the corresponding cone contrasts needed for detection of colour differences. The results reveal an invariance of cone contrasts at threshold for different states of chromatic adaptation. In other words, colour contrast signals at threshold follow Weber's law (doi: 10.1111/j.1475‐1313.2010.00773.x). A combination of RG and YB colour signals is needed to predict the colour threshold ellipse. The model relies on these findings and predicts how coloured filters external to the eye as well as pre‐receptor filters within the eye alter the measured RG and YB colour thresholds. Model predictions have been compared against measured colour thresholds using the CAD test (doi: 10.1093/bmb/ldx007). A number of experiments were carried out when the visual display was viewed with no lens in front of the eye or through a number of tinted lenses designed to absorb progressively more blue light.The effects of pre‐receptor filters within the eye such as the lens and the macular pigment have also been investigated. The results show that ‘blue‐blocking’ filters employed in typical spectacle lenses used with daylight illumination cause only small shifts, approximately along the daylight locus, without any significant loss of either RG or YB chromatic sensitivity. ‘Orange’ lenses that absorb greater amounts of short‐wavelength light cause a significant increase in YB thresholds, but have little or no effect on RG thresholds. More surprisingly, the model also predicts that the optical density of the macular pigment has little or no effect on the size of the colour threshold ellipse.Keywords: colour, cone contrasts, blue light, CAD test.

New methods for detection of early loss of rapid flicker, spatial vision, and chromatic sensitivity in glaucoma

Purpose: To examine whether ocular hypertension and early glaucoma cause measurable changes in spatial vision, rapid flicker sensitivity and red/green and yellow/blue colour vision.Methods: We examined subjects aged 40 to 78 years with ocular hypertension (OHT), primary open angle glaucoma (POAG), normal tension glaucoma (NTG), and age matched controls. Monocular best corrected visual acuity (BCVA) was tested using EDTRS charts.VA and Functional Contrast Sensitivity (FCS) with Landolt ring stimuli of both positive and negative contrast were also measured monocularly with the Acuity‐Plus test. Red/green (RG) and yellow/blue (YB) colour thresholds were measured with the Colour Assessment and Diagnostics (CAD) test. Photopic (cone‐enhanced) and mesopic (rod‐enhanced) rapid flicker thresholds were measured at the fovea (0°) and at an eccentricity of 5° in each of the four quadrants using the Flicker‐Plus test. All subjects had their visual fields measured using the Humphrey visual field analyser (24–2 SITA standard protocol). Peripapillary retinal nerve fibre layer thickness (pRNFLT) and macular retinal layer thicknesses were measured using the Heidelberg Spectralis OCT.Results: The mean, logMAR BCVA for OHT patients was 0.00 and for POAG and NTG patients was −0.10 and 0.10, respectively. For control participants, mean logMAR BCVA was 0.00. Mean pRNFL thickness was significantly reduced for glaucoma patients (59.5 ± 7.7 μm) as compared to control subjects (94.6 ± 5.13 μm) and OHT patients (115.5 ± 3.5 μm). POAG and NTG patients showed significantly higher colour thresholds (mean red/green threshold 4.97, blue/yellow 5.28 CAD units) compared to control subjects (mean red/green threshold 2.07, blue/yellow 1.62 CAD units). One OHT patient showed acquired loss of blue/yellow colour vision (3.23 CAD units), with normal VA. The Acuity‐Plus test which employs briefly presented stimuli, also revealed significant loss of VA (3.78 and 3.64 min of arc) and FCS (141.32% and 100%) in an NTG patient, with results outside normal limits for both positive and negative contrast, respectively. Central FCS was higher and outside the normal age limits for POAG patients (73.41% and 89.27%) as compared to age matched controls (61.27% and 33.63%). OHT patients, on the other hand, produced FCS thresholds within normal limits. Flicker modulation thresholds were higher for both rod and cone enhanced stimulus conditions in glaucoma and OHT patients, when compared to control subjects.Conclusion: The results reveal non‐uniform, losses that can affect selectively each of the visual attributes examined in this study. These preliminary findings suggest that in addition to VA and FCS tests, colour vision and rapid flicker sensitivity should also be examined in patients with optic nerve pathologies like glaucoma.

The use of colour and rapid flicker sensitivity tests for early detection and monitoring of vision changes in diabetes

Aims/Purpose: There is increasing evidence of impaired visual function prior to the presence of diabetic retinopathy (DR), yet current diagnostic criteria and treatment onset rely mostly on retinal vascular changes. In this study we measured changes in chromatic and rapid flicker sensitivity in subjects with prediabetes and diabetes to establish the value of such tests as a potential biomarker in the detecting early diabetes.Methods: Three groups of subjects were recruited: 1) normal controls, 2) subjects with prediabetes (HbA1c between 42‐47 mmol/mol), and 3) diabetics (with or without DR). Monocular cone‐ and rod‐enhanced flicker modulation thresholds (FMTs) were measured at the point of regard and in four parafoveal (5°) locations using the Flicker‐Plus test. Monocular red/green (RG) and yellow/blue (YB) colour thresholds were also measured at the fovea using the Colour Assessment and Diagnosis (CAD) test.Results: Both the RG and YB thresholds, as well as rod‐ and cone‐mediated flicker thresholds were significantly higher in both diabetic and prediabetic groups (when compared with healthy controls). When examined individually, ~50% and ~ 63% of the prediabetics and ~ 58% and ~ 70% of the diabetics revealed abnormal RG and YB thresholds, respectively (when compared with the upper normal limits for the corresponding age). HBA1c levels also revealed a positive trend with increasing RG and YB thresholds in the prediabetic group.Conclusions: In agreement with previous findings, both colour and FMTs are affected in patients diagnosed with diabetes. Unexpectedly, those deemed prediabetic that do not meet the clinical criteria for diabetes exhibit considerable loss of both colour and flicker sensitivity. The results suggest that colour and rapid flicker tests can provide useful information when screening for diabetes.

Association between chromatic sensitivity and peripapillary retinal nerve fibre layer thickness in healthy eyes

Purpose: Knowledge of the retinal structure—chromatic sensitivity relationship of healthy eyes would be important for early detection of retinal neuropathies such as glaucoma. This study investigated the association between colour vision thresholds and the thicknesses of the retina in healthy young eyes.Methods: Measurements were made in 56 healthy eyes of 56 young subjects of mean age 25 ± 2.4 years (range 20–31 years), and distance visual acuity ≤0.1 logMAR. Chromatic sensitivity was measured using the Color Assessment and Diagnosis (CAD) test. The macular thicknesses of the central fovea, parafovea, and macular ganglion cell complex (mGCC), and the thickness of the peripapillary retinal nerve fibre layer (pRNFL) were measured by spectral‐domain optical coherence tomography (SD‐OCT). Relationships between red‐green (RG) and yellow‐blue (YB) thresholds and the retinal thicknesses were examined through Spearman correlation.Results: Significant correlations were detected between pRNFL thickness, in the inferior hemisphere, and the RG and YB‐thresholds (r = −0.30, p = 0.03 and r = −0.31, p = 0.02; respectively). Decreased pRNFL thickness correlated with worse colour thresholds. No significant correlations were found between macular thicknesses and colour thresholds.Conclusions: Greater inferior pRNFL thickness was related to better chromatic sensitivity in healthy eyes of young subjects.

Development and validation of a new colour vision screener: A multi‐centre study

Aims/Purpose: The detection of acquired and congenital colour vision deficiency is of importance in the clinic for the early detection of ocular disease and determination of occupational suitability. Conventional methods of colour vision screening often fail to pass all normals and/or correctly identify those with acquired and congenital colour vision deficiency. The Colour Vision Screener (CVS) test [1] was developed to utilize an improved understanding of colour vision mechanisms to overcome the limitations present in conventional colour screening methods. This study aimed to use a robust multi‐centre methodology to fully validate the CVS test.Methods: Over 400 participants, including 124 normal trichromats, 166 deutans and 62 protans, were recruited from 10 international Colour Assessment and Diagnosis (CAD) testing centres. Each participant completed the CVS and the CAD test with calibrated visual displays. The red/green (RG) and yellow/blue (YB) CVS test sensitivity and specificity were established. The RG statistics were compared to the ‘gold standard’ reference for screening for RG congenital colour vision deficiency—the Ishihara pseudoisochromatic plate test.Results: The CVS test correctly identified ~99.1% of normal trichromats. All subjects with congenital RG loss and acquired loss on top of congenital RG deficiency were identified as having abnormal colour vision by the CVS. The Ishihara test, based upon 0 errors on the first 25 plates of the 38‐plate edition, correctly identifies ~80.6% of normal trichromats and 99.5% of subjects with congenital RG loss.Conclusions: Data collected across 10 international CAD centres demonstrate that the CVS can achieve a high sensitivity without sacrificing specificity. This multi‐centre study demonstrates that the CVS is quick, efficient, and easy to use and allows for the rapid and reliable screening of congenital and acquired colour vision deficiencies in large populations.Reference1. Barbur JL, Rodriguez‐Carmona M, Evans BEW. Colour vision assessment‐3. An efficient, two‐step, colour assessment protocol. Colour Research & Application 2021; 46: 33–45. https://doi.org/10.1002/col.22599

The value of assessing progressive loss of red/green and yellow/blue chromatic sensitivity in glaucoma

*Correspondence: franziska.rauscher@medizin.uni-leipzig.deThe value of assessing progressive loss of red/green and yellow/blue chromatic sensitivity in glaucoma.The study employed visual stimuli designed to isolate and reveal how spatial, temporal and chromatic aspects of visual processing change from normal sensitivity to extreme loss in glaucoma. The experiments carried out examined the fovea and each of four paracentral retinal regions, arranged diagonally away from fixation at an eccentricity of 6°. Spatial vision was investigated by measuring both absolute detection thresholds and functional contrast sensitivity using Landolt ring stimuli (Ophthalmic Physiol Opt 2022;42:1363–1378). These psychophysical tests based on Landolt C optotypes measure both detection thresholds and gap orientation discrimination thresholds in the same experiments using randomly interleaved test locations. First‐order motion perception was examined by using moving stimuli embedded in static luminance contrast noise. Red/green (RG) and yellow/blue (YB) colour thresholds were measured with the Colour Assessment and Diagnosis (CAD) test, which makes use of random, dynamic luminance contrast noise (±45%) to isolate the use of RG and YB colour signals. Subjects were normal controls (n = 65) and glaucoma patients with binocular visual field defects (n = 15) classified based on their Humphrey Field Analyser mean deviation (MD) scores. The impairment of visual function varied depending on the stimulus attribute and location tested. The severity of loss increased monotonically with disease progression. For subjects with mild glaucoma (MD −0.01 to −6.00 dB), significantly more data points exceeded the upper normal threshold limits for the corresponding age for RG colour thresholds than for any other visual test (Br Med Bull 2017;122:51–77), followed by motion thresholds. This was particularly the case for the parafoveal locations when compared with the equivalent thresholds measured at the fovea. The results suggest that a multifaceted measure of binocular visual performance based on foveal and parafoveal tests of RG colour vision and first‐order motion, can best inform on the progression of glaucoma and the overall loss of visual performance for comparison with other measures of changes in the quality of life in patients with glaucoma.Keywords: Glaucoma, Visual function, Colour vision, Motion detection, Contrast, Acuity, Colour Assessment and Diagnosis, CAD.

Cerebral achromatopsia

AbstractChromatic sensitivity was assessed in patients with pregeniculate and postgeniculate lesions. We examine changes in central vision along at foveal fixation and in each of the four paracentral quadrants of the visual field using the Colour Assessment and Diagnosis (CAD) test, a dynamic luminance contrast masking technique that isolates the use of Red / Green (RG) and Yellow / Blue (YB) colour signals. Because the extraction of colour signals in early visual processing involves opponent mechanisms, subjects with congenital RG loss of sensitivity exhibit symmetric increase in thresholds towards the long wavelength (“red”) and middle wavelength (“green”) regions of the spectrum locus. This is also frequently the case with acquired loss of chromatic sensitivity as a result of retinal or optic nerve disease. The findings from this study represent an exception to this rule. The patients investigated showed a marked asymmetry in colour thresholds. The study reveals how discrete, localized damage to visual pathways can cause selective loss of visual function and how the latter varies with retinal topography.The 36 pregeniculate patients investigated exhibited impairment in both RG and YB. Loss of colour vision was symmetrical for both RG and YB discrimination. Some pregeniculate patients exhibited substantial loss of colour vision in areas where perimetric loss was largely absent. All quadrants revealed similar symmetric loss of colour sensitivity.In 23 patients with postgeniculate lesions, patients with pre‐striate damage exhibited symmetric loss of chromatic sensitivity which affected either one or both chromatic mechanisms. Striate or extra‐striate lesions tended to exhibit general loss of colour vision within the area identified by visual field testing. More specific chromatic loss was associated with less impaired areas that were often normal on perimetric testing. Some patients with striate or extra‐striate lesions presented with asymmetric chromatic loss for one or more colour categories. When striate or extra‐striate lesions were also accompanied by underlying pre‐striate damage, chromatic sensitivity loss was always symmetric.The findings from this study show that the loss of chromatic sensitivity in cerebral achromatopsia depends strongly on the exact location and extent of the lesion with significant variation over the visual field. The same subject can exhibit loss of chromatic sensitivity that is either RG or YB specific, but also, spatially localized, non‐opponent loss of sensitivity for primary colours.

Colour‐related, binocular interactions in patients with dyschromatopsia

AbstractWe report findings of monocular and binocular assessments of colour vision and thresholds for rod‐ and cone‐mediated sensitivity in two young patients (P1 and P2) diagnosed with monocular dyschromatopsia. Altered, monocular, colour perception with no clear diagnosis was reported in each patient based on results from a number of clinical visual assessment tests carried out over several years. Electrodiagnostic tests also revealed reduced Yellow / Blue (YB) chromatic sensitivity in P1. Both patients exhibited unexpected binocular interactions of colour signals. This abstract focuses mostly on the results obtained in P1, but similar results using the same visual assessment tests will also be presented for P2.P1 experienced visual discomfort, often manifested as differences between monocular and binocular viewing, noise‐like appearance of uniform fields and colours over the field, when viewed monocularly with either eye. As a result of these reports, we re‐examined P1's visual deficits using the Colour Assessment and Diagnosis (CAD) and the Flicker‐Plus (FP) tests (http://www.city-occupational.co.uk/). The FP test measures rod‐ and cone‐mediated rapid flicker sensitivity centrally (along the direction of gaze) and at 6 deg eccentricity in each of the four quadrants.Colour Vision. P1 shows significant loss of YB colour vision when tested monocularly in the right eye, but normal red‐green (RG) and YB colour vision in the left eye. When tested binocularly, P1 continues to show the same loss of YB colour vision observed when using only the right eye. These results were unexpected since P1 shows ‘normal’ binocular summation for both colour and flicker sensitivity, even when the thresholds are above the normal range.Rod‐ / Cone‐sensitivity. The patient's cone‐mediated, flicker sensitivity at all five locations investigated (under binocular viewing) was normal (with flicker detection thresholds, often under 2%), but only for the cone‐enhanced condition. When tested with rod‐enhanced stimuli, P1 shows much reduced sensitivity with larger thresholds in the periphery, but only in binocular viewing. Such responses have not been observed previously.In conclusion, P1 shows loss of YB colour vision in the right eye and also significant loss of rod‐mediated sensitivity at each of the five locations investigated. The patient's cone mediated thresholds, at every location tested, were consistently below the mean expected for normal trichromats, both binocularly and with each eye. The YB colour vision measured binocularly remained severely abnormal with thresholds similar to the right eye, in spite of normal colour vision in the left eye. Preliminary observations also suggest that the patient's colour and rapid flicker sensitivity can be affected by fatigue and other factors.Although patient, P2, varied significantly to P1 in monocular thresholds, a similar binocular, inhibitory interaction between the two eyes was observed when processing colour signals. These observations and the unusual interactions between signals derived from the two eyes point towards abnormal central processing of colour signals.

Changes in visual function associated with hydroxychloroquine retinal toxicity

AbstractIntroduction: Non‐infectious inflammatory diseases, such as systemic lupus erythematosus, rheumatoid arthritis, dermatomyositis, antiphospholipid antibody syndrome and others cause significant morbidity and are treated with immunosuppression. Hydroxychloroquine (HCQ) sulfate is used as a second line immunosuppressant and has many advantages over other agents. These include increased life expectancy, reduced risk of neoplasia, reduced risk of diabetes and hypercholesterolaemia. HCQ is safe in pregnancy. After more than 5 years of treatment, HCQ can cause a degenerative maculopathy characterized by loss of parafoveal photoreceptors and RPE cells, leading to a ring‐like visual field defect. Current detection of early retinal toxicity relies on central visual field testing, optical coherence tomography (OCT) scan and fundus autofluorescence. The reason for the parafoveal predilection for retinopathy is not understood. HCQ is concentrated in melanin‐containing cells, and there is increased melanin concentration in the macular RPE cells. A hypothesis is that HCQ concentrated in the macular RPE cells leads to toxicity, with macular pigment protecting the fovea but leaving a ring of potentially vulnerable tissue in the parafoveal region. We were interested to investigate parafoveal function in patients with mild HCQ maculopathy and report the results of detailed macular function assessment of red/green (RG) and yellow / blue (YB) colour vision and rod‐ and cone‐mediated rapid flicker sensitivity.Methods: Two patients with confirmed early hydroxychloroquine maculopathy participated in the study. RG and YB colour thresholds were measured with the Colour Assessment and Diagnosis (CAD) test. Cone and rod‐mediated rapid flicker sensitivity was also measured in both central and paracentral vision using the Flicker‐Plus test. Both patients had taken HCQ for more than 15 years and had paracentral scotomas on 10–2 field test and loss of the parafoveal outer nuclear layer and ellipsoid layer, confirming the presence of maculopathy. To test the hypothesis of parafoveal toxicity risk, 20 short wavelength (BAF) and infrared wavelength (IRAF) autofluorescence images were reviewed. The BAF images are surrogate markers of the macular pigment and the IRAF the melanin concentration. Normalized maps of the difference between BAF and IRAF were calculated to investigate the possibility of a ring of vulnerable tissue.Results: Both patients had normal RG, but abnormal YB colour thresholds. One subject had normal cone flicker thresholds, but the rod flicker thresholds were raised in all quadrants in both eyes. The second subject had significantly elevated rod thresholds and elevated cone flicker thresholds in both eyes. Of note is that the degree of retinopathy in the second patient was greater than in the first. The areas of greatest threshold elevation correlated with the areas of greatest field loss and anatomical disruption on OCT.Conclusion: These new findings show that hydroxychloroquine retinopathy affects preferentially both YB colour vision and rod‐mediated flicker sensitivity. The cone‐mediated flicker sensitivity is also affected in more advanced disease. A model for the anatomical location of the toxicity will be presented, based on the hypothesis outlined above.

The value of colour assessment in diagnostic dilemmas

AbstractBackground: When the goal of clinical assessment is to segment, divide, and classify cases into neat discrete boxes it can often be frustrating to encounter cases which do not fit standard diagnosis algorithms. However, such diagnostic dilemmas often provide a valuable insight into the boundaries of current clinical procedures and the potential value psychophysical assessment can provide when used in conjunction with standard diagnosis algorithms. We present such a case involving localized retinal dysfunction that is not fully consistent with signs of either autoimmune retinopathy or occult maculopathy.Methods: Specific visual function loss was investigated in a health 32‐year‐old male with suspected localized retinal dysfunction, affecting the central retina. Blood tests and electro‐diagnostics were carried out after the patient presented with acute onset ‘foggy’ central vision. The working diagnosis from this initial visit was autoimmune retinopathy and oral steroids were prescribed. Following no change in symptoms a year after initially presenting, the patient was referred to City, University of London for bespoke assessments of specific visual functions. These included assessments of central and peripheral red / green (RG) and yellow / blue (YB) colour vision, mesopic visual acuity (VA), functional contrast sensitivity (FCS), rod‐ and cone‐mediated flicker sensitivity, and pupil responses measured using both rod‐ and cone‐enhanced stimuli.Results: The loss of vision affected primarily the central 20° with a mean VA of 6/36 in each eye. Fundus images, fluorescein angiography, and full field electroretinograms (ERGs) were normal, but pattern and focal ERGs were undetectable indicating localized dysfunction in central vision with OCT images showing a disrupted ellipsoid zone in each eye. The patient's mean corpuscular volume was 69 femtoliters, with red cell indices suggestive of thalassemia. Testing at City, University of London confirmed a loss of VA and FCS in the central 10° field, although both VA and FCS depended strongly on light level and were less affected with negative contrast stimuli. A loss of RG and YB colour vision was also measured centrally. Outside the central 10° field EA had almost normal colour and spatial vision. Rod‐ and cone‐mediated, flicker thresholds were elevated, with cone thresholds 10‐fold higher than normal. Pre‐stimulus pupil size, constriction amplitudes and latencies were normal with both centrally presented and peripheral stimuli.Conclusions: Psychophysical measurements in a patient with presumed autoimmune maculopathy showed atypical macular dysfunction that appears to preferentially affect negative contrast stimuli. Despite damage to the retinal mechanisms involved in spatial vision and light adaptation pupil responses remained unaffected. This unusual case highlights the importance of detailed phenotyping in understanding unknown aetiology.

Loss of colour vision in patients at risk of developing diabetes

AbstractRecent studies carried out in diabetic patients with no more than moderate maculopathy revealed that over 70% had significant losses of both Yellow/Blue (YB) and Red/Green (RG) colour vision (https://doi.org/10.1111/j.1755-3768.2012.F073.x). The purpose of this study was to investigate whether clinically ‘normal’ subjects, identified as being at ‘risk’ of developing diabetes show significant changes in rod‐ and cone‐mediated rapid flicker sensitivity as well as RG and YB colour vision.Three groups of subjects were recruited; a normal subject group (n = 40), a ‘high‐risk’ group (n = 150) and subjects diagnosed with diabetes (n = 23). The inclusion criteria for ‘high‐risk’ group required 3 or more recognized risk factors for diabetes (e.g., age > 45, HbA1C >5.7, high blood pressure, smoking history, high BMI, family history of diabetes, FPG levels >100 mg/dL). All subjects had full ophthalmic assessment and their RG and YB colour vision, Functional Contrast Sensitivity (FCS), Visual Acuity (VA) and Rod‐ and Cone‐mediated flicker sensitivity were measured using AVOT tests (https://researchcentres.city.ac.uk/applied-vision/avot).Consistent with previous findings, the diabetic group show significant loss of both RG and YB colour vision. Our findings show that these subjects also exhibit higher thresholds for rod and cone mediated vision. In addition, the ‘high‐risk’ group who are clinically classified as ‘normal’, also show significant loss of colour vision and rod and cone sensitivity. The latter group, do not, however, show significant differences in either VA or FCS. These findings suggest that accurate assessment of colour vision and rod‐ and cone‐ mediated rapid flicker sensitivity qualify as important risk factors in prediabetic screening.

Chromatic Contrast Sensitivity Functions and Colour Discrimination in Smoker Patients.

In this study, effects of smoking on colour vision with the Farnsworth–Munsell 100 Hue test (FM100h) and achromatic (A), red-green (RG), and blue-yellow (BY) contrast sensitivity functions were evaluated. In total, 50 non-smoker controls and 25 smokers, divided into two groups (group 1, less than 10 cigarettes per day, with 15 patients, and group 2, >10 cigarettes per day, with 10 patients) took part in the experiments. Best-corrected visual acuity (BCVA), FM100h, and A, RG, and BY contrast sensitivity functions were measured. Total and partial RG and BY error scores (TES and PTES) and colour axis index (CA) were used in the analysis. No differences between smoker and non-smoker groups were found in BCVA, CA and A and BY contrast sensitivity, but TES and PTES values and RG contrast sensitivity at 1 cpd were statistically different. Differences between smoker groups were not significant. Error scores in smokers were positively correlated with the number of cigarettes smoked per day, and in BY also with age. Tobacco caused discrimination losses in both chromatic mechanisms but affected the red-green pathway more than the blue-yellow, and therefore, a partial RG score of FM100h test seems to be a good predictor of smoker colour deficiencies.

Chromatic visual evoked potentials identify optic nerve dysfunction in patients with Graves' orbitopathy.

To explore visual dysfunction in Graves' orbitopathy (GO) objectively by analyzing chromatic visual evoked potentials (cVEP) and evaluate its diagnostic efficiency for dysthyroid optic neuropathy (DON). In this cross-sectional study, we analyzed pattern-reversal VEP (pVEP), red-green (R-G) and blue-yellow (B-Y) cVEP in 93 subjects (21 with DON, Group A, 30 with GO, Group B, and 42 healthy controls, Group C) at Wuhan Union Hospital, China. Compared with Group C, the amplitudes of B-Y cVEP were significantly lower in Group B, whereas all amplitudes of cVEP, latencies and amplitudes of pVEP in Group A were significantly impaired. In addition, the pVEP latency at 60 arcmin (60'), pVEP amplitudes and R-G cVEP amplitudes were significantly different between Group A and B. Moreover, 60'cVEP R-G negative-positive (N-P) amplitude was correlated with crowding index (P = 0.001), the average thickness of ganglion cell layer and inner plexiform layer (P = 0.004). Furthermore, combination of 60'cVEP R-G amplitude and 60'pVEP P100 latency had better diagnostic efficiency than each single parameter, with optimal cut-off values of 14.20μV and 110.65ms, respectively. GO may induce electrophysiological changes. The presence of B-Y cVEP anomalies in moderate to severe GO patients may be an early sign of preclinical DON. A decline in 60'cVEP R-G amplitude is associated with apical crowding and thinner inner intra-retinal layers. The combination of 60'cVEP R-G N-P amplitude and 60'pVEP latency can be a useful diagnostic index for DON.

Visual function deficits in eyes with resolved endophthalmitis

To evaluate the changes in functional vision in patients with resolved endophthalmitis. This was a cross-sectional study. The study included 20 patients with resolved endophthalmitis and best-corrected visual acuity of 20/100 or better. Visual acuity (VA), contrast threshold (CT), red/green (RG) and yellow/blue (YB) colour vision and 15 Hz flicker modulation threshold (FMT) were assessed using standard psychophysical techniques. The median age was 54 years. The median visual acuity was 0.27 (~ 20/40—Snellen Equivalent) ((interquartile range [IQR]), 0.30) logMAR). The median log contrast threshold (CT) was − 1.13 (IQR, 0.36) log units (normative value for age-matched CT: − 1.61 log units). The median red/green (RG) and yellow/blue (YB) thresholds were 11.52 (IQR, 26.19) and 9.45 (IQR, 16.20) CAD units respectively, which were at least 5 times higher than age-matched normative RG and YB thresholds. The median central cone- mediated FMT was 17.64% (IQR, 23.40%), which was much higher compared to age-matched FMT (5.48% [IQR, 3.47]). Linear regression revealed significant relationship between contrast thresholds and foveal thickness (y = 0.001x−1.47, R2 = 0.20, p = 0.048). Though endophthalmitis may resolve with a good visual acuity, deficits in visual functions like chromatic discrimination, cone-mediated flicker and contrast sensitivity persist.

Microextraction-colorimetric determination of anionic surfactants in natural and waste waters

An eco-friendly, simple, rapid and cheap method for determining anionic surfactants in natural and waste waters by microextraction-colorimetric method has been developed. The essence of the proposed approach consisted in extraction and concentration of analytes in an acidic medium in the form of associates with organic reagents (methylene blue and acridine yellow) by dispersion liquid-liquid microextraction using a mixture of chloroform-acetonitrile as an extracting and dispersing solvent, followed by aggregation of extractant microparticles by centrifugation and subsequent measurements of color characteristics using a smartphone. The values of the basic components of the RGB colorimetric system were used as an analytical signal to calculate the final color: The selection of optimal conditions for microextraction concentration of anionic surfactants from natural waters (the nature of the extracting and dispergating solvents, the volume of the dispergating solvent) was performed for the sodium dodecyl sulfate — methylene blue system. To study the colorimetric characteristics of the prepared extracts, a smartphone «iPhone X» was used as a color-registering device equipped with a specialized software product «RGBer». To minimize the measurement error by fixing the distance to the object under study and lighting conditions, we propose an installation that increases the accuracy and sensitivity of the determination and makes the method more mobile. The total content of the most common components of detergents was determined: sodium dodecyl sulfate, sulfonol, laureth sulfate and disodium laureth-3-sulfosuccinate. The detection limits ranged within 0.01 – 0.02 and 0.05 mg/liter. The range of detectable contents for all analytes was 0.05 – 1.0 mg/liter. For the determined surfactants, the equations of the relationship between the analytical signal and the concentration were obtained. The calibration graphs are linear with coefficients of the approximation reliability ≤0.98. The correctness of the method was tested on samples of natural water using the spike test procedure. The relative standard deviation of the analysis results does not exceed 0.13. The analysis duration is 20 – 30 min.

Age-related changes in visual search: manipulation of colour cues based on cone contrast and opponent modulation space

Reduced retinal illuminance affects colour perception in older adults, and studies show that they exhibit deficiencies in yellow-blue (YB) discrimination. However, the influence of colour cues on the visual attention in older individuals remains unclarified. Visual attention refers to the cognitive model by which we prioritise regions within the visual space and selectively process information. The present study aimed to explore the effect of colour on visual search performance in older observers. In our experiment, younger observers wearing glasses with a filter that simulated the spectral transmittance of the aging human lens and older observers performed two types of search tasks, feature search (FS) and conjunction search (CS), under three colour conditions: red-green, YB, and luminance. Targets and distractors were designed on the basis of the Derrington–Krauskopf–Lennie colour representation. In FS tasks, reaction times changed according to colour in all groups, especially under the YB condition, regardless of the presence or absence of distractors. In CS tasks with distractors, older participants and younger participants wearing glasses showed slower responses under chromatic conditions than under the achromatic condition. These results provide preliminary evidence that, for older observers, visual search performance may be affected by impairments in chromatic colour discrimination.

Color vision assessment‐3. An efficient, two‐step, color assessment protocol

AbstractColor vision tests and multi‐test protocols in current use often fail to detect small changes in red/green (RG) and yellow/blue (YB) color vision due to poor sensitivity. The tests also have low specificity. In this study, we examine how improved understanding of within‐ and inter‐subject variability in RG and YB color vision and accurate assessment of the differences in color thresholds between the least‐sensitive, age‐matched normal trichromats, and the least‐affected deutans and protans can be used to design an efficient color vision screener (CVS) test. To achieve this objective, we examined two extensive data sets from earlier studies and carried out new experiments to provide better estimates of within‐subject variability in color thresholds and to validate the CVS test. The data sets provide essential information on inter‐subject variability, the effects of normal aging on RG and YB thresholds, and the spread in RG color thresholds in deutan and protan subjects. A statistical model was developed to optimize the parameters of the CVS test and to predict the limits of what can be achieved in color assessment. The efficiency and repeatability of the CVS test were then assessed in 84 subjects. The results match model predictions and reveal close to 100% test efficiency. The test takes between 140 and 160 seconds to complete and has close to 100% repeatability. An efficient, “two‐step” protocol based on the initial use of the CVS test followed by full color assessment in only those who fail the CVS test is also described.

Chromatic visual evoked potentials indicate early dysfunction of color processing in young patients with demyelinating disease.

Chromatic visual evoked potentials (cVEP) primarily reflect the parvocellular visual pathway function, which has been shown to be predominantly affected in demyelinating disease (DD). The purpose of this study was to evaluate cVEP responses and to compare them with other structural and functional findings in young patients with DD. Thirty patients (8-28years of age) with DD with or without a history of optic neuritis (ON) were investigated. Twenty-five eyes had at least one episode of ON (ON-group) and 35 eyes had no clinically evident episode of ON (nON-group). OCT imaging was performed using a high-resolution spectral-domain OCT (SD-OCT), measuring retinal nerve fiber layer (RNFL) thickness. Pattern reversal electroretinography (PERG) and visual evoked potentials (VEP) were recorded according to the ISCEV standard, and chromatic visual evoked potentials (cVEP) were recorded to isoluminant red-green (R-G) and blue-yellow (B-Y) 7° circle stimuli, composed of horizontal sinusoidal gratings with spatial frequency 2 cycles/°, 90% chromatic contrast and onset-offset (300:700ms) mode of stimulation. Structural and functional measures were analyzed and compared between the groups. Both general (G) and temporal (T) RNFL thicknesses were reduced below normal limits in most of the eyes. However, in the ON-group (G: 77.5 ± 20.6, T: 51.4 ± 23.4µm), the thinning was more significant (p < 0.001) than in the nON-group (G: 95.4 ± 12.1, T: 70.1 ± 11.5µm). PERG N95 was within normal limits in the nON-group, while it was significantly more affected in the ON-group (7.4 ± 1.0 vs. 5.1 ± 2.0μV; p < 0.0001). Similarly, also VEP P100 latency and amplitude showed a greater percentage of abnormality in the ON-group, the latency being longer (117.2 ± 16.9 vs. 99.4 ± 4.6ms; p < 0.0001) and the amplitude lower (9.1 ± 5.1 vs. 16.4 ± 7.5μV; p < 0.0001). The cVEP N-wave amplitude to R-G and B-Y stimuli was reduced below normal limits in both ON- and nON-groups; however, cVEP to B-Y stimulation were slightly more affected in the ON-group (4.0 ± 3.8 vs. 5.9 ± 3.3µm; p = 0.02). A positive correlation between cVEP amplitude and RNFL thickness and between cVEP amplitude and PERG N95 amplitude, as well as a strong negative correlation between cVEP amplitude and P100 latency was observed. These findings demonstrate that cVEP indicate early abnormality of parvocellular pathway function in eyes with or without a history of optic neuritis and can be used together with other structural and functional parameters to evaluate visual pathway integrity of young patients with DD.