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At least 379 records · Page 21Linked to original sources
PubMed1979

Blue field entoptic phenomenon in cataract patients.

The blue field entoptic phenomenon (BFE), which allows the observation of one's own leukocytes flowing in macular retinal capillaries, was used to predict postoperative macular function in 136 consecutive patients undergoing uncomplicated cataract operation. The results were compared to those obtained with three commonly used tests: two-light discrimination, color perception, and the Purkinje vascular entoptic phenomenon. All four tests identified a nearly equal number of the good maculae (visual acuity 20/40 of better) ranging from 87% for the two-light discrimination test to 94% for the BFE test. However, the tests varied greatly in predicting poor macular function (visual acuity 20/50 or worse). The BFE test identified more than 75% of the poor maculae; the Purkinje vascular entoptic test and the two-light discrimination test, only 22%; and the color perception test, 11%. A positive response to the BFE test indicated a .98 probability of good macular function; a negative response indicated a .82 probability of poor macular function, predictions that were better than the other three tests or their combination.

Cataract↗
PubMed1976

Polymorphism of human color vision.

The genetic polymorphism of human color vision is examined within the framework of a photopigment replacement model. An analysis of the X-linked recessive dichromacies and anomalous trichromacies indicates that one source of variability of normal color perception may be the inclusion of several distinct phenotypes in what is usually described as normal color vision. This analysis also reveals the cause of the dominance hierarchy at the protan and deutan loci, the perceptual effects of dosage compensation, and the phenotypes of various compound hemizygotes.

Alleles↗
PubMed1975

Color and form perception on the Rorschach as a function of eye color.

Recent research had demonstrated that dark-eyed individuals are more reactive than light-eyed people. The present paper investigated one area of reactivity, ease of emotional arousal. The hypothesis that dark-eyed male subjects (n equals 40) would show greater ease of arousal than light-eyed male subjects (n equals 40) was tested using color and form responses on the Rorschach as dependent measures. The predicted interaction was significant; light-eyed subjects gave relatively more form responses, but dark-eyed subjects gave relatively more color responses. Implications for future research and application were discussed.

Arousal↗
PubMed1992

A bidimensional theory of achromatic color vision.

The theory is based on a perceptive color system where the achromatic colors are specified by their degree of similarity to the three qualities white, black and luminous. Black and luminous are treated as opponent variables. It is assumed that white and luminous/black are determined by different kinds of visual processes termed the w- and the b-process. The relationship between these processes and luminance parameters in a simple disc/ring configuration is derived from available data. The b-process is related to stimulus contrast in a simple manner. It is assumed to involve cells with antagonistic center/surround organization of the receptive field. The w-process is primarily determined by the local luminance, and it is assumed to involve cells that lack a center/surround organization of the receptive field. The w-process has properties similar to the processes involved in chromatic color vision. The theory can account for different kinds of psychophysical data on achromatic colors like data on simultaneous contrast, color scaling, and color constancy.

Color Perception↗
PubMed2005

Behavioral deficits and cortical damage loci in cerebral achromatopsia.

Lesions to ventral occipital cortex can produce severe deficits in color vision, a syndrome known as cerebral achromatopsia. Because most studies examine relatively few cases, however, uncertainty remains about precisely which cortical loci, when damaged, produce the syndrome. In addition, the extents of the associated perceptual deficits remain unclear. To address these issues, we performed a meta-analysis of 92 case reports from the literature. The severity of color vision deficits of the cases varied greatly, although nearly all showed some deficit in color discrimination. Almost all cases tested also showed some loss of spatial vision. Lesion overlap analyses revealed a relatively small region of high overlap in ventral occipital cortex. The region of high overlap was located near areas identified by neuroimaging studies as important for color perception. For comparison, we performed a similar analysis of prosopagnosia, a disorder of face perception, and found several regions of high lesion overlap adjacent to the region associated with achromatopsia. Because the behavioral deficits in achromatopsia are often incomplete and never restricted to color vision, the region of high lesion overlap may be one critical stage within a stream of many visual areas that participate nonexclusively in color perception.

Cerebral Cortex↗
PubMed2002

Color and defective color vision as factors in the conspicuity of signs and signals.

The conspicuity of road traffic signs and signals for a group of observers with the color vision defect of deuteranopia is compared with that for a control group of observers with normal color vision. Conspicuity was measured by the proportion of reports of target objects detected in 300-ms presentations of projected slides of road scenes. There were two instructions, one designed to measure attention conspicuity and the other, search conspicuity. The attention conspicuity of red, orange, and green color-coded traffic control devices was significantly less for deuteranopes than for the observers with normal color vision, but this was not true for yellow and blue color-coded signs. This result is consistent with our understanding of the color perceptions of deuteranopes. The reduction of conspicuity was not so great for the search conspicuity condition. We conclude that redundant color coding does contribute to the conspicuity of signs and signals and that deuteranopes--and probably those with other severe forms of defective color vision--have a significantly reduced ability to notice colored targets, such as road signs and signals, in complex visual environments. The actual and potential application of this work is in the design of signs so they are conspicuous, especially when the user group includes people with defective color vision.

Adolescent↗
PubMed2001

Video color perimetry: impairment in glaucoma suspects.

PURPOSE: To detect mild visual field impairment in asymptomatic glaucoma suspect patients. METHODS: Color perception within the visual field was tested with customized color video perimetry. The key features of the system were stimuli color desaturation, low-level luminance and equiluminant gray background. Twenty patients with asymptomatic glaucoma were tested and compared with a group of age-matched control subjects. RESULTS: Automated perimetry test findings differed significantly in the two groups, particularly for short-wavelength sensitivity (blue). The severity of color impairment correlated directly with intraocular pressure. CONCLUSION: Desaturated low-luminance video perimetry will reliably detect and quantify asymptomatic visual field defects. A previous work on multiple sclerosis has detected a mild long-wavelength (red) impairment in asymptomatic patients after an episode of optic neuritis, even in clinically unaffected fellow eyes. Our findings in glaucoma suspect patients indicate that a mild blue impairment could be the initial sign of this disease.

Adult↗
PubMed1991

[The molecular genetics of color blindness].

The gene structures of three color pigments have been reported by Nathans et al. in 1985. One copy of red gene and 1 to 3 copies of green genes are tandemly repeated on X chromosome. As the structures of red and green genes are highly homologous (96%) and tandemly repeated, they cross-over on chromosome during meiosis and hybrid genes were produced. The function of these hybrid genes exhibits abnormal spectrum for red and green light. The 5' portion of the gene determines which cone cell type express the gene and the 3' portion of the gene determines the type of spectrum. In the 3' portion, exon 4 are associated with a small shift of spectrum and exon 5 determines a large shift of spectrum. For example, a hybrid gene with 5' region of red and 3' region of green is expressed in the red cones and exhibits green spectrum. Abnormality of color perception depends on the hybrid ratio of red and green genes.

Base Sequence↗
PubMed1999

Color vision deficits and laser eyewear protection for soft tissue laser applications.

PURPOSE: Laser safety considerations require urologists to wear laser eye protection. Laser eye protection devices block transmittance of specific light wavelengths and may distort color perception. We tested whether urologists risk color confusion when wearing laser eye protection devices for laser soft tissue applications. MATERIALS AND METHODS: Subjects were tested with the Farnsworth-Munsell 100-Hue Test without (controls) and with laser eye protection devices for carbon dioxide, potassium titanyl phosphate (KTP), neodymium (Nd):YAG and holmium:YAG lasers. Color deficits were characterized by error scores, polar graphs, confusion angles, confusion index, scatter index and color axes. Laser eye protection device spectral transmittance was tested with spectrophotometry. RESULTS: Mean total error scores plus or minus standard deviation were 13+/-5 for controls, and 44+/-31 for carbon dioxide, 273+/-26 for KTP, 22+/-6 for Nd:YAG and 14+/-8 for holmium:YAG devices (p <0.001). The KTP laser eye protection polar graphs, and confusion and scatter indexes revealed moderate blue-yellow and red-green color confusion. Color axes indicated no significant deficits for controls, or carbon dioxide, Nd:YAG or holmium:YAG laser eye protection in any subject compared to blue-yellow color vision deficits in 8 of 8 tested with KTP laser eye protection (p <0.001). Spectrophotometry demonstrated that light was blocked with laser eye protection devices for carbon dioxide less than 380, holmium:YAG greater than 850, Nd:YAG less than 350 and greater than 950, and KTP less than 550 and greater than 750 nm. CONCLUSIONS: The laser eye protection device for KTP causes significant blue-yellow and red-green color confusion. Laser eye protection devices for carbon dioxide, holmium:YAG and Nd:YAG cause no significant color confusion compared to controls. The differences are explained by laser eye protection spectrophotometry characteristics and visual physiology.

Adult↗
PubMed2001

The dissociation of color from form and function knowledge.

We report on two brain-damaged subjects who exhibit the uncommon pattern of loss of object color knowledge, but spared color perception and naming. The subject P.C.O., as in previously reported patients, is also impaired in processing other perceptual and functional properties of objects. I.O.C., in contrast, is the first subject on record to have impaired object color knowledge, but spared knowledge of object form, size and function. This pattern of performance is consistent with the view that semantic information about color and other perceptual properties of objects is grounded in modality-specific systems. Lesion analysis suggests that such grounding requires the integrity of the mesial temporal regions of the left hemisphere.

Adult↗
PubMed2004

[The analysis of refractive error in children and adolescents from 6-15 years of age based on 1000 examinations in two major Polish regions].

PURPOSE: The aim of this study is to present the results of screening examinations of refractive errors, taken on 1002 of school children ranging from 6 to 15 years of age. MATERIAL AND METHODS: As the result of Internet screening visual acuity and color perception tests named "I can see..." in 10,021 children from randomly chosen schools in Poland in the year 2002, the group of 1002 children was chosen. In this group, the subjective and objective refractive error examination was taken as well as the visual acuity test, color perception with the use of Ishihara tables and full ophthalmologic examination. RESULTS: Average visual acuity was RE: 0.72 (SD +/- 0.31) and LE: 0.72 (SD +/- 0.31). The prevalence of emmetropia was 34%. In the examined group myopia in 17%, hyperopia in 20%, astigmatism in 5.5% of children was found, and in 24.5% of patients complex errors occur such as myopic and hyperopic astigmatism.

Adolescent↗