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Following an apparent left parietal CVA, a patient developed a severe and nearly complete color amnesia which was not associated with any disturbance in color vision or color perception. Like all previously reported cases with color amnesia, this patient was alexic but, unlike most previously reported cases, he was not aphasic.
An experimental study of Allergan's Oxysept Comfort system was performed by measuring the slight reddish hue that appears in the disinfecting solution, indicating to the users that their lenses are again ready to be worn. The temporal evolution of the color of the solution has been measured under standardized conditions and analyzed in the CIELAB system, from the perspective of the typical threshold discrimination of the human eye. Color differences between neutralized and non-neutralized solutions occurred in an appropriate direction of the color space to enhance discrimination and were clearly perceptible by normal observers (greater than 9.7 +/- 1.2 CIELAB units). Colorimetric analyses have been used to draw conclusions regarding observers with defective color vision. The color of the solution changes abruptly, approximately 25 min after the neutralization process begins, and remains nearly constant after about 60 min, this agreeing well with the temporal evolution of the hydrogen peroxide concentration.
The classical twin method was used to examine the genotype--phenotype relationship in color vision. Suprathreshold color differences were assessed by 5 pairs of monozygotic (MZ) and 3 pairs of dizygotic (DZ) twins. The control group included 3 unrelated normal trichromats, a non-twin sibling pair, and a previously diagnosed deuteranomal. Concordance rates were calculated by Spearman's correlation coefficients (rs) and Procrustean distances (gl) between the reconstructed color spaces for each related pair of observers. For 4 pairs of the MZ twins, the rs values were comparable to intraindividual variability in the control normal trichromat; they were significantly higher (0.94-0.97) than those for the DZ twins and siblings (0.72-0.82). The gl values for the MZ twins (0.008-0.029) were lower than for the DZ twins (0.073-0.079) and siblings (0.053). The high concordance between each pair of the MZ twins suggests that their shared photopigment genome constrains a contribution of possible individual variations in nongenetic factors to variability of their color spaces. Lower concordance rates in the DZ twins and siblings can be attributed to differences in the inherited arrays of photopigment genes. Contributions to intrapair variation in color spaces of twins from cognitive factors such as perceptual-cognitive color categorization and decision-process variability are discussed.
Malingering is the conscious creation of a functional defect or denial of a true defect. Positive malingering is the former, and negative malingering is the latter. Hysteria is similar to malingering except that it is unconscious. Ocular malingering is common among draft evaders. The flight surgeon or military ophthalmologist will more commonly see the negative malingerer in peacetime because of the high physical standards for flying. Wartime creates a sudden shift towards positive malingering, however, for obvious reasons. This paper carefully defines the distinctions between malingering, hysteria, and true disease consistent with the defect claimed. It also provides a systematic approach to history, examination, and special testing of a possible ocular malingerer/hysteric. A number of common ocular complaints are considered separately, including decreased visual acuity, visual field defects, night vision defects, color vision defects, ocular muscle defects, automutilatory defects, opacification of transparent media, blepharospasm, intraocular disease, and asthenopia.
Individual differences in abnormal color vision are well known. A fundamental unresolved problem is the great variation in color vision even among those classified as having the same color-vision defect. Several physiological hypotheses have been proposed to account for this variation but little consideration has been given to how (and how much) color matching and discrimination are affected by the posited physiological mechanisms. Advances in molecular genetics have renewed interest in this problem, which is at the foundation of the relation between genotype and phenotype. We report here theoretical Rayleigh ranges (chromatic discrimination) and quantal matches for deuteranomalous trichromats with photopigments in the red/green range that vary in their separation and optical density. The results show there is relatively little loss of discrimination with pigments of normal optical density separated by as little as 2-3 nm. With pigments separated by 4 nm or less, however, optical density can strongly influence discrimination when varied independently in the two types of cone. Moderately lower (or higher) optical density in only one cone-type affects discrimination by altering the shape of the cone's relative spectral sensitivity function. The lack of correlation between Rayleigh-match midpoint and range, which is reported in the literature, may be accounted for by independent variation in pigment separation and optical density.
The classification of neutral grays is helpful for the differential diagnosis of color vision defects, especially when anomaloscopic examination is not possible. In congenital color vision defects the PR, RP region of the spectrum appears 'dark' to protan-defective subjects and 'light' to deutan-defective subjects. Acquired color vision defects have a common base type, the type III blue-yellow defect. The defect develops depending on the site of the primary lesion and also on the fixation mode. Classification of neutral grays may help in differentiating optic nerve diseases from retinal diseases; when visual functions become mediated by rods, sensitivity shifts and the BV, B region of the spectrum will appear relatively 'light' to the patient.
PURPOSE: To determine the underlying molecular genetic basis of a retinal dystrophy identified in a 4-generation family and to examine the phenotype and the degree of intrafamilial variability. DESIGN: Prospective case series. PARTICIPANTS: Six affected individuals from a nonconsanguineous British family. METHODS: Detailed ophthalmologic examination, color fundus photography, autofluorescence imaging, and electrophysiologic assessment were performed. Blood samples were taken for DNA extraction, and mutation screening of GUCA1A, the gene encoding guanylate cyclase-activating protein 1 (GCAP1), was undertaken. RESULTS: All affected subjects complained of mild photophobia and reduced central and color vision. Onset was between the third and fifth decade, with subsequent gradual deterioration of visual acuity and color vision. Visual acuity ranged between 6/9 and counting fingers. Color vision was either absent or markedly reduced along all 3 color axes. A range of macular appearances was seen, varying from mild retinal pigment epithelial disturbance to extensive atrophy. Electrophysiologic testing revealed a range of electrophysiologic abnormalities: isolated cone electroretinography abnormalities, reduced cone and rod responses (with cone loss greater than rod), and isolated macular dysfunction. The 4 coding exons of GUCA1A were screened for mutations in affected and unaffected family members. A single transition, A319G, causing a nonconservative missense substitution, Tyr99Cys, segregated uniquely in all affected subjects. CONCLUSIONS: The Tyr99Cys GUCA1A mutation has been previously shown to cause autosomal dominant progressive cone dystrophy. This is the first report of this mutation also causing both cone-rod dystrophy and isolated macular dysfunction. The phenotypic variation described here exemplifies the intrafamilial heterogeneity of retinal dysfunction that can be observed in persons harboring the same mutation and chromosomal segment.
We examined the effects of probing human color mechanisms using sinusoidal spectral power distributions (SPD's) varying in frequency (i.e., from 0.1 to 5.0 cycles/300 nm for a constant starting phase) and phase (i.e., from 0 to 360 deg for a fixed frequency of 1 cycle/300 nm) through computer simulation using several color models. Predicted modulation sensitivity functions (MSF's) in spectral frequency and phase differ among the models and indicate that measurements of the minimum amplitudes necessary to detect sinusoidal SPD's would be useful for distinguishing among theories of color vision. MSF's obtained from similar analyses of dichromats' color mechanisms reveal characteristic patterns of modulation sensitivities and suggest that such measures could serve to distinguish type and degree of color-vision defect. Some implications based on sinusoidal approximations to illuminant and reflectance spectra are discussed along with more general considerations regarding sine-wave SPD's as a probe for mechanisms of color vision.
We determined the genotypes of the X-chromosome-linked red/green color vision genes by a novel PCR/SSCP-based method and assessed expression by mRNA analysis in retinae of 51 unselected post mortem eye specimens from Caucasian males of unknown color vision status. All individuals had a single red (long-wave) pigment gene and one or more (an average of two) green (middle-wave) pigment genes. Four males had 5'green-red3' hybrid genes in addition to normal red and green pigment genes. These findings are consistent with earlier studies on human visual pigment gene structure using Southern blotting and with a recent study using pulsed-field electrophoresis. We interpret claims of much larger numbers of red, green and green-red hybrid genes to be technical artifacts. The ratio of expressed red to green pigment retinal mRNA varied widely (1-10 with a mode of 4) and was not correlated with that of red to green pigment genes. In one individual with a green-red hybrid gene in addition to normal red and green pigment genes, the normal red pigment gene and the hybrid gene were both expressed, but the normal green gene was not. This person presumably had deuteranomalous color vision. Two with green-red hybrid genes expressed the normal red and green pigment genes, but not the hybrid genes. These two individuals presumably had normal color vision. We interpret the failure to express their green-red hybrid genes to be caused by their location at a more distal position in the visual pigment gene array.
PURPOSE: The aviation signal light gun (LG) is believed by some to be the only color-critical task in aviation without redundant coding. However, there are questions regarding its practicality as a test of color vision given that the brightness and colors may vary between airports. METHODS: The chromaticity coordinates and relative intensities of five LGs were measured with a portable spectroradiometer. Four of the LGs were measured at airports in southern Ontario and compared with a newly purchased LG (ATI Avionics). The air traffic controllers (ATCs) were also surveyed regarding the frequency of LG use. RESULTS: Only 40% of the LGs at the airports were in good working condition. All working LGs met the ICAO standards for airport signal lights. However, differences did exist between models which were related to the date of manufacture. Older LG lights were dimmer and their green and white lights were more yellow than the newer LGs. ATCs reported that they used the LG primarily for pilot instruction and demonstration. However, in two locations, the LG was used to signal pilots who were flying their aircraft in for radio repair. This occurred about once or twice a month. DISCUSSION: The LG is used primarily for instructional purposes. However, if a radio repair shop is at the airport, then the LG will be used about once to twice a month. There is sufficient variability in the light colors and intensity across airports so that any given LG cannot be used as valid practical test of color vision in aviation.
PURPOSE: The authors examined the influences of diabetes on the results of visual function testing in patients with ocular hypertension (OHT). METHODS: Color vision (desaturated D-15), contrast sensitivity together with both transient and steady-state pattern electroretinogram (PERG) findings from patients with documented OHT were examined in a historic cohort study. All patients were examined at least four times (mean, 7.8 examinations) during a follow-up period that ranged from 1.5 to 4 years. Only individuals who maintained normal visual fields throughout the follow-up period were included in this analysis. The sample included 158 patients with OHT. Of these patients, 32 were African-American and 23 had a history of noninsulin-dependent diabetes with no evidence of retinopathy (by ophthalmoscopy). Normative data were obtained from a control group that included 65 white subjects with normal vision who did not have diabetes and who were similar in age to the patients in the OHT group. RESULTS: Color vision, contrast sensitivity, and PERG results were reduced significantly in patients with diabetes and OHT relative to control subjects. Patients with OHT who did not have diabetes did not have similar abnormalities. Color vision and PERG results also were reduced significantly in patients with diabetes and OHT relative to those with OHT who did not have diabetes. Only the steady-state PERG was reduced in African-American patients with OHT (relative to both control subjects and white patients with OHT). CONCLUSIONS: Patients with diabetes and OHT have significantly greater color vision, contrast sensitivity and PERG abnormalities than patients with OHT without diabetes. Race factors do not play a major role in these differences. Screening for diabetes is recommended before drawing conclusions from the results of these types of functional tests in patients with OHT.
BACKGROUND: The Holmes-Wright lantern (Type A) is an approved occupational color vision test for airline pilots in the European Economic Community and for specific occupations in the British Armed Forces. The colors shown are red, green and white signal lights. HYPOTHESIS: The Holmes-Wright lantern is a sensitive screening test for red-green color deficiency in photopic viewing and the pass/fail level is similar to that of the Farnsworth Lantern (Falant) if the same scoring method is applied. METHOD: There were 138 color deficient subjects identified with the Ishihara plates and diagnosed with the Nagel anomaloscope, completed a color vision test battery which included three runs of the nine color pairs of the Holmes-Wright lantern at high brightness in normal room illumination. RESULTS: Screening sensitivity on a single error was found to be 97% compared with the Ishihara plates. Using the Falant scoring method, 20 subjects passed. These were 1 deuteranope, 2 protanomalous trichromats and 17 deuteranomalous trichromats (22% of 88 anomalous trichromats). The mean error score was greater for protans than for deutans but the mean number of qualitative error categories was smaller. Green/white confusions were the most frequent errors. It was not possible to predict who would pass the lantern test from other test results but all subjects with a Nagel anomaloscope matching range > 15 scale units who failed the Farnsworth D15 test or were grading as moderate/severe with the American Optical Company (Hardy, Rand and Rittler) plates failed. CONCLUSIONS: The Holmes-Wright lantern is a sensitive screening test for red-green color deficiency. Although a similar percentage of anomalous trichromats fail the Holmes-Wright lantern as fail the Falant, if the same scoring method is used, the superior correlation between the Holmes-Wright result and other color vision tests designed to grade the severity of color deficiency suggests that the two lantern results are not equivalent.
Unrelated patients with achromatopsia, macular degeneration with onset under age 50 years, cone degeneration or dysfunction, cone-rod degeneration, or macular malfunction were screened for mutations in the three genes known to be associated with achromatopsia: the GNAT2 gene encoding the alpha subunit of cone transducin and the CNGA3 and CNGB3 genes encoding the alpha and beta subunits of the cone cGMP-gated cation channel. We found no examples of patients with GNAT2 mutations. Out of 36 achromats, 12 (33%) had mutations in CNGA3 (13 different mutations including five novel mutations) and 12 (33%) had mutations in CNGB3 (six different mutations including four novel mutations). All achromats with CNG mutations had residual, presumably cone function as determined by computer-averaged 30-Hz electroretinograms (ERGs). There was considerable variability in acuity and color vision, with most patients having acuities of 20/200-20/400 and complete absence of color perception, and others having acuities of 20/25-20/40 and some color vision. Two pseudodominant achromatopsia cases were uncovered, both with CNGA3 mutations, including one family in which some compound heterozygotes with achromatopsia mutations were clinically unaffected. We found two novel CNGB3 changes in three patients with juvenile macular degeneration, a phenotype not previously associated with mutations in the cone channel subunits. These patients had subnormal acuity (20/30-20/60), normal to subnormal color vision, and normal to subnormal full-field cone ERG amplitudes. Our results indicate that some patients with channel protein mutations retain residual foveal cone function. Based on our findings, CNGB3 should be considered as a candidate gene to be evaluated in patients with forms of cone dysfunction, including macular degeneration.
PURPOSE: To describe the color vision disturbance reported by patients in whom a clear intraocular lens (IOL) was implanted in one eye and a yellow-tinted (blue-light-absorbing) IOL in the other eye. DESIGN: Retrospective interventional case series. METHODS: Data recorded included demographic information, dates of surgery, IOL model and power (manufacturer is the same for all lenses), best-corrected visual acuity, and subjective visual complaints. RESULTS: Four of five patients had no spontaneous color vision complaints. When these patients were informed of the unintended mismatch, all remarked that they could perceive a color vision difference, but that it was not bothersome. One of the five patients reported "beige" vision. None of the patients wanted an IOL exchange. CONCLUSION: Many patients can tolerate the color vision imbalance that results when a clear IOL is implanted in one eye and a yellow-tinted IOL is implanted in the other eye.
Future helmet mounted systems and cockpit displays will rely on color graphics and information that high performance aircraft pilots will need to discern and understand. Color in displays may help reduce pilot workload. The effect of high G and reduced eye level blood pressure on field-of-view has been study extensively. The effect of high sustained acceleration on color vision, however, is unknown. Research on visual contrast sensitivity, night vision, and visual acuity under acceleration in a human centrifuge has demonstrated changes in vision. We began by having normal color vision subjects view a magnified color aerial map and describe what they saw as we slowly ramped up the G profile from baseline (1.4 G) at 0.1G/sec until they experienced almost complete blackout. At that point subjects began straining and the centrifuge was rapidly decelerated. Several subjects described the river fading away before much else happened. Then the yellow and green features of the terrain faded together. Reds and dark blues appeared to change to black but remained legible until the entire image also faded to black. Computer types call the color of a river on a map cyan. So a display was created that resembled a device know as a "light bar" that is routinely used in centrifuge research. It consisted of a 45 degree wide square projection of green dots in the periphery and a red dot in the center on a white background. Due to our new curiosity about cyan we added dots halfway between the green and red that were cyan. We then ran several people through the same slow onset ramp until near blackout. Several reported that the cyan disappeared completely, significantly before the green. Then the green disappeared, and finally the central red dot. For those who experience it, it is a very useful and repeatable early end point where vision is affected but still available. Next we borrowed a color wheel from the hypobaric chamber and taped it to the wall of the cab. Several subjects reported discomforting angular optical vection due to torsional nystagmus. Thus, a vertical bar arrangement of colors was selected that minimized disruption from involuntary eye movements.
Exposure to organic solvents, which are widely used in industry, can lead to dysfunction of the nervous system. However, controversy continues about the nature of early-stage damage to the nervous system from low-grade chronic exposure to organic solvents. Since loss of color-vision can be a sensitive early marker of neurotoxic damage, the main aim of this study was to investigate the association between low-level chronic exposure to organic solvents, especially benzene, and acquired dyschromatopsia. The study initially comprised 1236 workers who were employed at a large petrochemical distillation factory. After excluding those workers who may have had color-vision impairment due to congenital or acquired eye diseases and those with other medical conditions, 908 males who had worked for at least 6 months were included in the final analysis. Those who worked only in the office were categorized as nonexposed, while those who worked at outside facilities were divided into three groups of approximately equal size according to their estimated cumulative exposure levels to benzene (low, medium, high). Color-vision was assessed using the Lanthony D-15 desaturated panel color test. The results showed that the color-confusion index (CCI) was positively related to age. In the qualitative assessment of types of color-vision loss, the prevalence of total dyschromatopsia was significantly higher with increasing cumulative exposure levels in the left eye (p<0.05) but not in the right eye. The significance for the prevalence of type III dyschromatopsia was borderline in the left eye (p=0.0571). The relationship between acquired dyschromatopsia and exposure level also showed an increase in the odds ratio in the left eye but not in the right eye. Taken together, these results suggest that chronic low-level exposure to benzene can lead to acquired dyschromatopsia.
Air traffic controllers perform a variety of tasks which require them to identify, discriminate, and name colors. Qualification standards for this occupation require applicants and incumbents to have normal color vision. The validity of this standard has been questioned and is currently under review. In this study, 22 deutans and 78 normals were tested on a set of tasks which simulated critical tasks performed daily by air traffic controllers. The four tasks included discriminating red from black pencil marks on flight progress strips, color-naming of 1 degree and 0.1 degree discs, and identification of colored line segments embedded in a multicolored background. Deutans classified as mild were found to perform all tasks as well as normals. Moderate deutans performed only the large disc color-naming task as well as normals, whereas severe deutans performed none of the tasks as well as normals. Different methods for scoring the color vision tests were explored to determine their value as predictors of task performance. The D-15 relative error score was found to be the single best predictor of performance on the tasks (r-square = 0.602). It is concluded that mild deutan color defectives have adequate color vision for safe performance of several critical air traffic control tasks. Moderate and severe deutans do not. In addition, the results of several methods for scoring color vision tests can be used to predict group, but not individual, performance with high reliability.
We analyzed the data obtained from the Malbrel chromatometer, a device that examines color vision. The principle of the chromatometer is based on the opponent chromatic receptive fields of the retina. It shows two adjacent luminous windows of small size that can be either red and green or yellow and blue. The patient's task is to adjust the brightness of the red window (or the yellow window) to a fixed green (or blue) window luminance. Several luminance levels were studied and data were recorded using specific software. The luminance and the chromatic coordinates of the windows have been determined. The aim of the statistical study was to compare the data with a simple distribution law and therefore to know if the chromatometre allows measurement of color vision. In this investigation, 95 eyes were studied. Each patient has to match 4 red/green brightness levels and 4 yellow/blue brightness levels. The main characteristics were evaluated: the means, medians and standard deviations. Then, from the qq-plots we verified that the data distribution was near normal distribution. The percentile curves allowed 3 types of color vision to be determined. Around the median normal color vision can be defined. Between the 10(th) and the 20(th) percentiles and between the 80(th) and the 90(th) percentiles, a small anomaly was present. Below the 10(th) percentile or above the 90(th) percentile, a substantial anomaly was present.