Chromatic discrimination in fixed saturation levels from tufted capuchin monkeys with different color vision genotypes.

Recent research has proposed new approaches to investigate color vision in Old World Monkeys by measuring suprathreshold chromatic discrimination. In this study, we aimed to extend this approach to New World Monkeys with different color vision genotypes by examining their performance in chromatic discrimination tasks along different fixed chromatic saturation axes. Four tufted capuchin monkeys were included in the study, and their color vision genotypes were one classical protanope, one classical deuteranope, one non-classical protanope, and a normal trichromat. During the experiments, the monkeys were required to perform a chromatic discrimination task using pseudoisochromatic stimuli with varying target saturations of 0.06, 0.04, 0.03, and 0.02 u'v' units. The number of errors made by the monkeys along different chromatic axes was recorded, and their performance was quantified using the binomial probability of their hits during the tests. Our results showed that dichromatic monkeys made more errors near the color confusion lines associated with their specific color vision genotypes, while the trichromatic monkey did not demonstrate any systematic errors. At high chromatic saturation, the trichromatic monkey had significant hits in the chromatic axes around the 180° chromatic axis, whereas the dichromatic monkeys had errors in colors around the color confusion lines. At lower saturation, the performance of the dichromatic monkeys became more challenging to differentiate among the three types, but it was still distinct from that of the trichromatic monkey. In conclusion, our findings suggest that high saturation conditions can be used to identify the color vision dichromatic phenotype of capuchin monkeys, while low chromatic saturation conditions enable the distinction between trichromats and dichromats. These results extend the understanding of color vision in New World Monkeys and highlight the usefulness of suprathreshold chromatic discrimination measures in exploring color vision in non-human primates.

Combined influence of medication and symptom severity on visual processing in bipolar disorder.

Previous studies have reported visual impairments in patients with bipolar disorder (BPD), but unclear were whether clinical variables would be associated with those disturbances. Here, we investigate the relationship between visual functioning, in terms of color discrimination, and the impact of BPD duration, mood state, and the patients' medication. Forty-five participants (25-45 years old) were recruited for this study. Color discrimination was performed using the Cambridge Colour Test. Serial multiple mediations were run to investigate the assumption of association between color discrimination and the clinical variables. Our findings showed that, compared with healthy controls, BPD patients' performance was worse for the Protan, Deutan, and Tritan vectors, revealing deterioration of color discrimination. In addition, the mediation analyses revealed a strong direct (p < .001) and moderate-to-high indirect effects (p < .01) of medication and symptom severity on color discrimination. Overall, both longer the duration of the disease and greater the symptom severity of BPD patients resulted in worse performance. It highlights the importance of examining the wider clinical context of an affective disorder to understand how it affects visual processing in this population.

Heavy and light smokers have slight differences in chromatic discrimination.

Objectives: The effects of smoking on color vision have been scarcely studied. To bridge such gap, this study examined if there were differences in chromatic discrimination between heavy and light smokers. Methods: The psychophysical Trivector test was used to evaluate chromatic discrimination in healthy controls (n = 36), heavy smokers (n = 29), and light smokers (n = 32). The subject's task was to identify the orientation of the Landolt C ring gap - presented and randomized in one of the four positions (e.g., up, down, right, and left). Results: The thresholds for Protan (red), Deutan (green) and Tritan (blue) were higher in heavy smokers compared to nonsmokers but not to light smokers. Conclusions: The results confirm that heavy smoking and chronic exposure to its harmful compounds affect color discrimination when compared to light smoking; and this is more pronounced in heavy smokers than light smokers. This is particularly important to understand the differences among smokers on visual and multisensory processing.

Melanopsin driven enhancement of cone-mediated visual processing.

The precise control of visual sensitivity to variations in external lighting is critical for optimising human visual function in a changing environment. In photopic illumination, the cone photoreceptors and their post-receptoral pathways have a primary role in regulating these adjustments; it is not fully understood how a small population of melanopsin-expressing, intrinsically photosensitive retinal ganglion cells (ipRGCs) can interact with the three cone photoreceptor classes to modulate human visual function. Here we investigated interactions between these inner and outer retinal photoreceptor classes in participants with trichromatic colour vision under conditions that independently controlled the excitations of ipRGCs, cones and rods in the retina. In the peripheral retina, we show that interaction between melanopsin- and cone-directed signals affect conscious, image-forming vision. The interaction patterns are inconsistent with any potential effects arising from artefacts due to open-field and penumbral-cone contrasts, or rod intrusion. For cone signals mediated via each of the three primary visual pathways, melanopsin activation enhances contrast sensitivity. The contrast response functions indicate this enhancement is a more generalised facilitation effect that onsets at ∼9% melanopsin contrast. The implication for human vision is that the contrast sensitivity of cone-mediated visual processes can be modulated by the level of melanopsin excitation in the stimulus light.

New iPAD-based test for the detection of color vision deficiencies.

PURPOSE: To develop and validate a new iPad-based color vision test (Optopad). METHODS: A total of 341 student eyes were enrolled in a first comparative study between Optopad and the Isihara tests. In a second comparative study, Optopad vs. the Farnworth-Munsell test (FM 100H), a total of 66 adult eyes were included. Besides the agreement between tests, the correlation between FM 100H and Optopad outcomes were investigated. Multiple regression analysis was used to predict the total error score (TES) from contrast thresholds measured with the Optopad test. RESULTS: The Ishihara and Optopad tests detected the same anomalous patients. Concerning FM 100H vs. Optopad, 10 subjects were diagnosed as anomalous with both tests, 3 mild anomalous cases based on TES were classified as normal with Optopad, and 2 anomalous subjects based on Optopad test showed normal TES values. Statistically significant correlations of TES and partial error red-green (PTESRG) with thresholds measured with the red-green Optopad stimuli were found. A multiple quadratic regression model was obtained relating TES and chromatic contrast values from Optopad (R2 = 0.855), with only 13 cases showing residuals of ≥ 25 units. CONCLUSIONS: The design and implementation of a chromatic contrast discrimination test has been carried out, with promising clinical results. This test seems to provide comparable outcomes to those obtained with Ishihara and FM 100H tests.

Calidad de vida relativa a la visión según estudios psicofísicos en pacientes hipermétropes con cirugía facorrefractiva / Quality of life relative to the vision according to psychophysical studies in hyperopic patients undergoing phaco-refractive surgery

Objetivo: describir los resultados de la calidad visual para la mejoría de la discriminación cromática, así como la estereopsia y la sensibilidad al contraste, posterior a la cirugía facorrefractiva en pacientes hipermétropes mayores de 40 años, y si la mejoría visual es sustancial en los parámetros de función visual según estudios psicofísicos. Métodos: se realizó un estudio descriptivo, longitudinal y prospectivo a 70 pacientes operados en el período de enero a diciembre del año 2016, hipermétropes présbitas con buena visión corregida, atendidos en el Servicio de Microcirugía del Instituto Cubano de Oftalmología "Ramón Pando Ferrer", quienes mostraron mejoría subjetiva en su calidad de vida al disminuir la dependencia de los espejuelos. Se realizó un estudio de sensibilidad al contraste con la cartilla de Pelli-Robson; discriminación cromática con la prueba de Farnsworth Munsell 100-Hue y estereopsia a través de la prueba de The Netherlands Organization. Resultados: hubo una mejoría significativa en todos los exámenes realizados. La sensibilidad al contraste pasó de una media en el prequirúrgico de 1,44 cd/m2 a 1,56 cd/m2 en el posquirúrgico. La prueba FMH-100 mejoró cuantitativa y cualitativamente (de 142,06 errores en el pre, bajó a 52,91 en la poscirugía); predominaron discriminadores promedios con 50 pacientes y 13 altos discriminadores; mejoró la estereopsia con y sin cristales después de la cirugía, lo que pudo cuantificarse. Conclusiones: hay una mejoría objetiva de la calidad visual después de la lensectomía refractiva en el paciente hipermétrope, demostrada en los resultados de la discriminación cromática, la estereopsia y la sensibilidad al contraste(AU)

Objective: describe visual quality results related to improved chromatic discrimination, stereopsis and contrast sensitivity after phaco-refractive surgery in hyperopic patients aged over 40 years, and determine whether substantial visual improvement is achieved in visual function parameters according to psychophysical studies. Methods: a prospective longitudinal descriptive study was conducted of 70 presbyopic hyperopic patients with good corrected vision undergoing surgery from January to December 2016 at the Microsurgery Service of "Ramón Pando Ferrer" Cuban Institute of Ophthalmology, who experienced subjective quality of life improvement on reducing their dependence on eyeglasses. Contrast sensitivity was evaluated with the Pelli-Robson chart, chromatic discrimination with the Farnsworth Munsell 100-Hue test and stereopsis with The Netherlands Organization test. Results: significant improvement was observed in all the tests performed. Contrast sensitivity rose from a preoperative mean of 1.44 cd/m2 to 1.56 cd/m2 in the postoperative period. Results of the FMH-100 test improved both quantitatively and qualitatively (from 142.06 errors in the preoperative period to 52.91 in the postoperative period); average discriminators prevailed with 50 patients and 13 high discriminators; stereopsis improved after surgery with and without glasses, which could be quantified. Conclusions: objective quality of life improvement is observed in hyperopic patients after refractive lensectomy, as is evidenced by chromatic discrimination, stereopsis and contrast sensitivity results(AU)

Is discrimination enhanced at the boundaries of perceptual categories? A negative case.

The human visual system imposes discrete perceptual categories on the continuous input space that is represented by the ratios of excitations of the cones in the retina. Is discrimination enhanced at the boundaries between perceptual hues, in the way that discrimination may be enhanced at the boundaries between speech sounds in hearing? In the chromaticity diagram, the locus of unique green separates colours that appear yellowish from those that appear bluish. Using a two-alternative spatial forced choice and an adapting field equivalent to the Daylight Illuminant D65, we measured chromatic discrimination along lines orthogonal to the locus of unique green. In experimental runs interleaved with these performance measurements, we obtained estimates of the phenomenological boundary from the same observers. No enhancement of objectively measured discrimination was observed at the category boundary between yellowish and bluish hues. Instead, thresholds were minimal at chromaticities where the ratio of long-wave to middle-wave cone excitation was the same as that for the background adapting field.

Long-term loss of color vision after exposure to mercury vapor

We evaluated the color vision of 24 subjects (41.6 ± 6.5 years; 6 females) who worked in fluorescent lamp industries. They had been occupationally exposed to mercury vapor (10.6 ± 5.2 years) and had been away from the source of exposure for 6.4 ± 4.04 years. Mean urinary concentration of mercury was 40.6 ± 36.4 æg/g creatinine during or up to 1 year after exposure and 2.71 ± 1.19 æg/g creatinine at the time of color vision testing or up to 1 year thereafter. All patients were diagnosed with chronic mercury intoxication, characterized by clinical symptoms and neuropsychological alterations. A control group (N = 36, 48.6 ± 11.9 years, 10 females, 1.5 ± 0.47 æg mercury/g creatinine) was subjected to the same tests. Inclusion criteria for both groups were Snellen VA 20/30 or better and absence of known ophthalmologic pathologies. Color discrimination was assessed with the Farnsworth D-15 test (D-15) and with the Lanthony D-15d test (D-15d). Significant differences were found between the two eyes of the patients (P < 0.001) in both tests. Results for the worst eye were also different from controls for both tests: P = 0.014 for D-15 and P < 0.001 for D-15d. As shown in previous studies, the D-15d proved to be more sensitive than the D-15 for the screening and diagnosis of the color discrimination losses. Since color discrimination losses were still present many years after the end of exposure, they may be considered to be irreversible, at least under the conditions of the present study.