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PubMed1995

Survey of colour contrast sensitivity in non-ophthalmic users of blue-green wavelength argon lasers.

BACKGROUND: Previous studies have shown that ophthalmologists using blue-green argon laser may suffer subtle defects in their colour vision. A reduction in colour contrast sensitivity in the tritan colour confusion axis, an early manifestation of blue cone photoreceptor injury by the high energy photons of the laser, has been demonstrated and has prompted a reappraisal of laser safety in ophthalmology. Argon laser is also frequently used in scientific research, often at higher power output and for longer periods than is used in clinical practice. The scientists operating these lasers are at risk of developing similar phototoxic retinal injury. METHODS: The colour contrast sensitivity of 18 scientists who regularly use short wavelength argon laser was investigated. RESULTS: Eye protection was infrequently used and individuals had been subjected to between 580 and 7200 hours of cumulative laser exposure during the course of their research. CONCLUSION: The use of blue-green argon laser by the scientists investigated was not associated with a significant reduction in colour contrast sensitivity.

Adult↗
PubMed1998

Blue-yellow colour vision in an onchocercal area of northern Nigeria.

AIM: To determine if the City University Tritan Test is a useful addition to visual function assessment in rural communities in northern Nigeria. METHODS: The study was a cross sectional survey. The participants were 8394 people, aged 5 years and over, living in 37 rural communities, mesoendemic and nonendemic for onchocerciasis, in Kaduna State in northern Nigeria. The main outcome measures were the detection of a defect in blue-yellow colour vision by two criteria: (1) failure with the City University tritan screening plates; (2) failure with the City University grading plates to identify severe tritan defects. RESULTS: 91% of those aged 10 years and above could perform the test. Below this age, there were difficulties in comprehension. The test showed good inter- and intraobserver agreement. After adjustment for confounders the odds of failing the screening plates were significantly increased in the presence of optic atrophy or glaucoma (3.55 (2.48-5.08) and 15.9 (4.22-60.2) respectively). There was a greater increase in the adjusted odds of failing the grading plates in the presence of optic atrophy or glaucoma (5.30 (2.97-9.45) and 8.87 (1.61-48.7) respectively). Cataract had a smaller effect on the screening plates, adjusted odds 1.63 (0.95-2.80). CONCLUSION: Blue-yellow colour vision testing is a useful addition to visual function assessment in those aged 10 years and above in rural northern Nigeria, particularly in the detection of optic nerve disease.

Adolescent↗
PubMed1995

Gene conversion between red and defective green opsin gene in blue cone monochromacy.

Blue cone monochromacy is an X-linked condition in which the function of both the red pigment gene (RCP) and the green pigment gene (GCP) is impaired. Blue cone monochromacy can be due to a red/green gene array rearrangement existing of a single red/green hybrid gene and an inactivating C203R point mutation in GCP. We describe here a family with blue cone monochromacy due to the presence of the C203R mutation in both RCP and GCP. The flanking sequences of the C203R mutation in exon 4 of RCP were characteristic for GCP, indicating that this mutation was transferred from GCP into RCP by gene conversion.

Base Sequence↗
PubMedDate not supplied

Familial Kallmann syndrome with unilateral renal aplasia.

On the basis of studies in two brothers and their double first cousin, the Kallmann syndrome (KS) is discussed as an X-linked syndrome of anosmic hypogonadotropic hypogonadism. The anosmia is thought to represent agenesis or hypoplasia of the olfactory lobes, the mildest form of the alobar holoprosencephaly developmental field defect; this is supported by the finding of hypotelorism in two of the patients and their mother. The endocrine defect is thought to represent a hypothalamic abnormality of the luteinizing hormone releasing hormone; borderline normal intelligence may represent another pleio-tropic CNS manifestation of the KS gene. All three affected males had unilateral renal aplasia, associated in one with ipsilateral absence of the testis. The presence of at least two developmental field defects (involving the CNS and urogenital system) makes it likely that the KS is a true multiple congenital anomaly syndrome; this is supported by the finding of additional, mostly minor, anomalies reported by other investigators. Heterozygous females may also show manifestations of anosmia, hypogonadism, possibly even internal genital malformation; however, genetic heterogeneity of anosmic hypogonadism is possible, and for the time being it is probably better to designate sporadic female cases of anosmic hypogonadism as examples of the olfacto-genital syndrome of DeMorsier. Linkage studies are urgently needed to clear up the question of genetic heterogeneity and to help develop empiric recurrence risk figures in anosmic hypogonadism.

Adult↗
PubMed1968

The luminosity curve of the protanomalous fovea.

Threshold spectral sensitivities (in the dark, or against bright colored backgrounds) are identical in the red-green range for both protanopes (dichromats) and protanomalous trichromatic color defectives. The latter, however, must have an additional photolabile cone pigment in the red-green range, and its presence is revealed by heterochromatic brightness matching through the spectrum (i.e. luminosity curves). The absorption spectrum of the anomalous cone pigment can be inferred from the protanomalous and protanopic luminosity curve, given reasonable assumptions as to how the different cone mechanisms pool their responses. Depending upon these assumptions, the pigment inferred is either (a) dilute solution of the normal red pigment (assumed density 1.0 for the deuteranope) or (b) similar in its absorption spectrum to the normal green pigment but shifted slightly toward the long wave end of the spectrum. Experimental attempts to choose between these alternatives have so far proved equivocal though (b) seems more likely on the basis of indirect evidence.

Color Perception Tests↗
PubMed1995

Horizontal cells function normally in ethambutol-treated goldfish.

Ethambutol, a tuberculostatic drug, induces red-green colour vision defects in man and goldfish. The ethambutol-induced red-green colour vision defect in goldfish was argued to originate in the retina because after ethambutol application: (1) inhibitive interactions in red-green (double) opponent ganglion cells are lost [Van Dijk & Spekreijse, 1982 (Investigative Ophthalmology and Visual Science, 24, 128-133); Wietsma & Spekreijse, 1992 (Investigative Ophthalmology and Visual Science Suppl., 33, 1032)] and (2) the depolarizing responses to red light in the biphasic horizontal cells are reduced. To account for these findings Spekreijse, Wietsma and Neumeyer [(1991) Vision Research, 31, 551-562] suggested that ethambutol induced dark adaptation in the retina. In this paper the dark adaptation hypothesis is tested with the following results: (1) ethambutol changes only transiently the receptive field size and spectral sensitivity of horizontal cells; (2) the spectral characteristics of horizontal cells do not change in long-term ethambutol-treated goldfish; (3) formation of spinules on horizontal cell dendrites in cone terminals, a parameter for light adaptation, remains unaffected. Therefore we conclude that ethambutol does not induce functional dark adaptation of horizontal cells and that the ethambutol-induced red-green colour vision deficiency does not originate in the horizontal cell layers.

Action Potentials↗
PubMed2005

Impact of congenital colour vision defects on occupation.

AIMS: To investigate whether there is an association between congenital colour vision defects (CVD) and occupational choice and employment history, in order to inform the debate about the value of universal childhood screening for these disorders. METHODS: Participants were 6422 males and 6112 females from the 1958 British birth cohort, followed from birth to 33 years, whose colour vision was assessed (Ishihara test) at 11 years. RESULTS: A total of 431 males (6.7%) had CVD. Men with CVD had pursued some careers for which normal colour vision is currently regarded as essential; for example, eight men (3.1%) with CVD were in the police, armed forces, or fire-fighting service at 33 years compared to 141 men (3.8%) with normal colour vision. They were, however, under-represented compared to those with normal colour vision, in other occupations; for example, no men with CVD were employed in electrical and electronic engineering at 33 years compared to 15 men (0.4%) with normal colour vision. CONCLUSIONS: The findings of this study suggest there is little to be gained by continuing with existing school screening programmes for CVD, whose primary purpose is to advise affected children against certain careers. Other ways of informing young people about potential occupational difficulties and pathways for referral for specialist assessment are likely to be more useful.

Career Choice↗
PubMed2000

Neurological deficits in solvent-exposed painters: a syndrome including impaired colour vision, cognitive defects, tremor and loss of vibration sensation.

Five individuals are described who had participated in a study of former dockyard painters. All had worked between 16 years and 45 years as industrial painters, much of the time inside ships. All underwent structured neurological examination, colour vision testing (allowing calculation of a colour confusion index corrected for age and alcohol), and detailed psychometric testing. An occupational history sufficient to allow estimation of past exposure to solvents was taken. All gave a history of exposure to high concentrations of solvents at work, and several described episodes of acute narcosis. All showed neurological deficits and some had overt neurological disease, although in no case had this previously been linked to their work. The most striking features, sufficient to constitute a syndrome, were acquired blue-yellow colour vision deficits, coarse tremor, impaired vibration sensation in the legs and cognitive impairment. Their estimated cumulative exposures to solvents ranged between the equivalent of 13 and 37 calendar years working at the Occupational Exposure Standard concentration (OES years). This study for the first time gives an indication of the concentrations of solvents likely to lead to serious neurological disease in humans. It serves as a reminder to physicians to take an occupational history from patients with obscure neurological or psychological impairment.

Aged↗
PubMed2003

Visual dysfunction in retinal and optic nerve disease.

Visual perceptions seen with retinal and optic nerve disease may overlap with those resulting from retrochiasmal disorders. A few disorders typically present with distinctive perceptions, but the majority have less specific symptoms. Features include whether or not the visual phenomena are negative or positive, monocular or binocular, and the location and form of any deficits. Among negative phenomena, transient visual loss usually is the result of ischemic disease, but particular precipitants may suggest demyelination or photoreceptor degeneration. The pattern and location of visual field defects may help localize disorders to the level of the macula, papillomacular or other inner retina nerve fiber bundles, optic nerve, or chiasm. Altered brightness perception may point to optic nerve or photoreceptor disease. Decreased acuity is among the most common and least specific symptoms, but association with other symptoms may help to narrow the differential diagnosis. Dyschromatopsia points to either a photoreceptor or optic nerve pathologic condition (Table 7). Among positive phenomena, hallucinations resulting from anterior visual system disorders typically are unformed, although deafferentation of retrochiasmal pathways may produce formed hallucinations. The common "floaters" frequently are benign, but occasionally herald more concerning disorders. Various types of photopsias commonly occur with vitreal disorders or photoreceptor disorders. Macular disease typically leads to distortions of the central visual field, and other particular disorders lead to a host of characteristic distortions of color, form, or brightness. Careful attention to the ophthalmologic examination, visual fields, and subtle variance in symptomatology also help to distinguish among various disorders.

Color Vision Defects↗
PubMed1981

A new class of visual defect. Spreading inhibition elicited by chromatic light stimuli.

This paper deals with a single male subject, M., who has a well-defined visual defect of a kind not previously described. The defect is associated with a potent inhibitory response to long-wavelength stimuli, which spreads for up to 12 deg from the area of stimulation, suppressing M.'s detection of other high contrast stimuli. The effect can also be observed, weakly, with certain other coloured stimuli, but not with yellows or whites. Detailed psychophysical data are given for threshold sensitivity, colour matching, two-colour increment thresholds and visual acuity, all of which are more or less abnormal, depending on the stimulus colour. No abnormal effects were, however, observed with white light stimuli. On the basis of M.'s ability to fuse red and green random dot stereogram pairs, we argue that the inhibition arises centrally in the visual pathways. and we examine the implications of M.'s response characteristics for the analysis of central visual processing.

Adult↗
PubMed1991

Two systems for colour-naming defects: verbal disconnection vs colour imagery disorder.

Two subjects affected by pure alexia and showing no central dyschromatopsia or generalized aphasia, performed poorly on traditional tasks with visually-presented colour stimuli and on tasks with objects presented verbally. Three experiments were conducted to evaluate the possible role of mental colour imagery in recalling the colours of objects from memory. It was concluded that Case I, with left occipital lobe softening, had preserved imagery systems, but failed to recode the colours of mentally generated colour images, just as he failed to name visually presented colours, suggesting a language-imagery disconnection. In contrast, Case II, with a bilateral occipital lesion, had sustained damage to her long-term visual memories for colours as chromatic attributes of objects. This content-specific imagery deficit was concomitant with colour agnosia. The present findings are discussed in terms of current cognitive theories on imagery deficits.

Aged↗
PubMed1998

Medical, morphological and functional aspects of Greek football referees.

OBJECTIVE: The aim of the study was to investigate state of health, morphological and functional profile of football referees (Rs). EXPERIMENTAL DESIGN: A prevalence study. PARTICIPANTS: 188 Greek active male Rs of A, B, C and D football divisions have been evaluated. MEASURES: Standard clinical-instrumental and anthropometric methods were used. Appropriate functional tests were used for evaluation of visual performance, physical condition and mental ability. RESULTS: Mean age, height, weight, and BMI were 36.3 +/- 4.5 years, 177.4 +/- 5.7 cm, 81.6 +/- 7.8 kg, and 25.9 +/- 2.1 kg.m-2 respectively. 64% and 6% were overweight and obese respectively. In 27.2% resting blood pressure exceeded upper normal limits. Active (41.5%) and former smokers (17.0%) were identified. Visual acuity and colour discrimination were defective in 2.4% and 0.7% respectively. Stereo depth perception deficiently in 7.1%. Compared to international standards, Rs' mean scores in the 6 physical condition field tests were found satisfactory. All Rs were found efficient in the agility test, two-thirds in the maximal and prolonged speed tests and half of them in the endurance test. Relatively more Rs of A and B divisions were found fit as compared to Rs of C and D divisions. Average IQ score was 112.5 +/- 11.1, while about 90% and 34% of the Rs' IQ score was > or = 100 and > or = 120 respectively. CONCLUSIONS: Average male Greek football R is an apparently healthy, young to middle aged, rather overweight, and functionally efficient. The great majority of Rs of A and B divisions appear better trained and somewhat better functional than Rs of C and D divisions.

Adult↗
PubMedDate not supplied

Electrophysiological findings in dominant optic atrophy (DOA) linking to the OPA1 locus on chromosome 3q 28-qter.

Pattern and flash visual evoked cortical potentials (PVEP, FVEP), and pattern electroretinograms, (PERG) were recorded in 13 affected individuals from 8 families with DOA. These were selected as representative from 87 affected members of 21 pedigrees with DOA who were examined, and who underwent genetic linkage analysis. Linkage to the OPA1 locus on chromosome 3q 28-qter was demonstrated in all families. VA ranged from 6/9 to HM: visual fields showed a variable centro-caecal defect; SLO (when performed) showed diffuse nerve fibre loss; MRI (when performed) showed small intra-orbital optic nerves. In 9/13 patients the PVEP was absent in one or both eyes. Most recordable PVEPs were of abnormal latency, but the delays were not marked (peak times 116-135 msec); amplitudes were low or subnormal. PERG fell within the normal range in 9 eyes of 7 patients. 14 eyes showed an abnormal N95:P50 ratio in keeping with ganglion cell dysfunction. Some severely affected eyes showed P50 component involvement, but in no eye was the PERG extinguished. Significant interocular asymmetries in at least one electrophysiological measure were present in 6/13 patients. Colour contrast thresholds were significantly elevated for all three colour confusion axes, with tritan being most affected.

Adolescent↗
PubMed1993

Colour vision anomalies following experimental glaucoma in monkeys.

Spectral sensitivity defects, associated with chronic elevated intraocular pressure (IOP) produced by Argon laser trabeculoplasty, were studied in monkeys. Increment-threshold spectral sensitivity (ITSS) and threshold versus intensity (TVI) functions were measured using a behavioural model. Elevated IOP resulted in short wavelength (SW) sensitivity losses characteristic of many ocular diseases. The amount of SW sensitivity loss for ITSS functions depended upon the intensity level and chromatic composition of the background field. The optimum condition identifying the greatest SW sensitivity reduction was a yellow background of moderate intensity (100-1000 Td). In the early stages of experimental glaucoma, the cone mechanisms and the rod mechanism typically showed decreased test and field sensitivities. The SW cone pathway has slightly greater threshold elevation (approximately 0.3 log unit) compared to the rod and cone pathways. On the other hand, in the advanced stages of experimental glaucoma, the largest sensitivity losses were in the longer-wavelength, red-green opponent mechanisms, with the rod and SW cone pathways showing smaller losses. The similarities of the colour vision anomalies in this animal model with those of patients with glaucoma, provides support for its use as an experimental model for human glaucoma.

Animals↗
PubMed1997

Clinical use of the City University Test (2nd Edition).

The City University test (TCU test) aims to identify people with significant colour deficiency and to classify the type of defect. 222 people with congenital red-green colour deficiency, diagnosed with the Nagel anomaloscope, were examined with the TCU test (2nd Edition). All deuteranopes and 44% of deuteranomalous trichromats failed the TCU test. Deutans who failed could be subdivided into two categories of severity depending on whether errors were made on five or more plates. 96% of protanopes and 26% of protanomalous trichromats failed. Protans made fewer errors than deutans and subcategories of severity could not be distinguished according to the number of errors made. The Farnsworth D15 test was found to be more effective than the TCU test in identifying significant protan colour deficiency. Detection and classification rates varied on all the plates of the TCU test. Mixed protan and deutan classification errors were made by 61% of subjects with the majority result correct in 80%. The most efficient plates are identified and recommendations are made for the optimum use of the TCU test in clinical practice.

Color Perception Tests↗
PubMed2001

A disorder of colour perception associated with abnormal colour after-images: a defect of the primary visual cortex.

A 64 year old woman with posterior cortical atrophy secondary to probable Alzheimer's disease is described. Her presenting symptom was of seeing objects as abnormally coloured after prior exposure to a coloured stimulus. Formal testing disclosed that the patient experienced colour after-images of abnormal latency, duration, and amplitude.The demonstration of prolonged colour after-images in a patient with a cortical disease process provides strong evidence that the generation of colour after-images is mediated at least in part by the visual cortex. A mechanism for the generation of colour after-images is proposed in which abnormal prolongation of the images results from excessive rebound inhibition of previously excited wavelength selective neurons in V1. This may occur as a consequence of the relative sparing of inhibitory interneurons in V1 in the context of the degeneration of excitatory neurons that occurs in Alzheimer's disease.

Afterimage↗
PubMed1995

Colour contrast sensitivity in patients with age-related Bruch's membrane changes.

Patients with bilateral drusen as a manifestation of early age-related macular degeneration (AMD) may have minor psychophysically detectable visual defects in the presence of normal visual acuity. In a variety of retinal diseases, one of the earliest changes in visual processing is an impairment of normal colour vision. This study was undertaken to evaluate colour vision deficits in patients with macular drusen and to determine whether changes in colour contrast sensitivity may occur over time. In a prospective study, colour vision in 84 eyes of 84 patients aged 55-84 years (mean, 68.89 +/- 6.23 years) with macular drusen and clear media was tested using a computer graphics technique. A total of 47 patients were reviewed annually for up to 2 years and measurements were obtained at annual intervals. Colour contrasts sensitivity along protan, deutan and tritan colour confusion lines was determined at a foveal and a parafoveal region. The sensitivity to all stimuli showed large variations between patients. The thresholds for foveal blue-colour contrast sensitivity were elevated and increased during the review period. In contrast, there was no significant change in sensitivity with time for red and green at the foveal or parafoveal region. Tritan threshold changes suggest that the SW cone-receptor population is more susceptible to damage associated with early age-related macular disease than are red or green cones. The results indicate that blue colour contrast sensitivity determined over time may serve as a measure to assess the progression of age-related maculopathy prior to the manifestation of atrophic or exudative macular lesions associated with visual loss.

Aged↗
PubMed1968

The luminosity curve of the deuteranomalous fovea.

Analogous to protans, the two types of deutan color-defectives-the dichromats (deuteranopes) and the anomalous trichromats (deuteranomalous)-do not differ in spectral sensitivity in the red-green range at threshold (either in the dark or against bright colored backgrounds). However, luminosity curves obtained by heterochromatic brightness matching show the latter to be slightly more sensitive in the blue-green, and slightly less so in the red, than the former. Experiment proves that these differences are due (at least in part) to contributions of cones containing the deuteranomalous anomalous pigment which are missing from the deuteranope's eye. The absorption spectrum of the anomalous pigment can be inferred with assumptions (analogous to those already made with protanomalous trichromats) about how the different cone mechanisms pool their responses to yield luminosity. Two alternatives thus revealed are (a) the normal red pigment in dilute solution or (b) a spectrum very similar to that of the normal red pigment but shifted slightly toward the short wave end of the spectrum. Since the spectrum inferred by (a) has the same lambda(max) as the normal red pigment, (a) predicts that deuteranomalous observers will require a negative red primary when matching monochromatic lights of wavelengths near the lambda(max). This is not observed.

Color Perception Tests↗