Color Defects Research Articles

Repeatability of the Holmes-Wright Type A Lantern Color Vision Test

Recent studies showing a lack of internal consistency for the Holmes-Wright Type A Lantern (HWA) raise the issue as to whether the lantern test is repeatable. This study determines the HWA repeatability for several scoring criteria. There were 78 individuals with normal color vision (NCV) and 80 individuals with defective color vision (DCV) who were tested during two separate visits. Three runs of the test lights were always presented in dim room illumination. An additional dark-adapted run was presented during both visits for a subset of 61 subjects. Repeatability was evaluated for the following pass/fail criteria: the Joint Aviation Requirements, Farnsworth's criterion, the Commission Internationale de l'Eclairage criterion for the HWA, a perfect performance, and the 99th and 100th percentile scores of the NCV sample. The NCV agreement for passing both sessions was high, with 96% having a perfect score at both sessions. The DCV agreement for passing both sessions was lower, ranging from 0.62 to 0.80. Criteria which stopped the test after a perfect performance on the first run had the lowest values. The DCV agreement for failing both sessions was high, ranging from 0.97 to 0.99. Stopping the test after a perfect performance on the first run should be abandoned. Presenting three runs of the nine test lights and allowing no more than two errors is repeatable, passes all the NCV, and minimizes the number of individuals who pass the lantern at the first session and fail at a later session.

Defective Colour Vision. I-Its Nature

The various types of defective colour vision are described with particular reference to the sensations experienced. Two theories of colour vision, the trichromatic and opponent–colours theories, are described briefly and the recent objective proof of both is reviewed.

Reduction of drosopterin content caused by a 45-nt insertion in Henna pre-mRNA of Drosophila melanogaster

Phenylalanine hydroxylase is assumed to be a key enzyme in drosopterin metabolism, but direct in vivo evidence to support this hypothesis is still absent. In the present study, we found a new natural recessive purple eye mutant of Drosophila melanogaster, Hn ( bp ), which was a 45-nt insertion mutant in the second exon of Henna. The insertion resulted in a predicted protein with 15 additional amino acids as compared to the wild-type protein. Further analysis of protein structure showed that the predicted mutant protein probably had two more beta-sheets, which may cause instability of two alpha-helices near the catalytic centre of the enzyme in the Biopterin-Hydroxyl binding domain. Hn ( bp ) mutant showed eye color defect with decrease of mRNA level, as well as drosopterin content reduction. The drosopterin defect could be fully rescued by expression of wild type Henna in the Hn ( bp ) background by GMR-GAL4 UAS-Henna/UAS-Henna:Hn ( bp )/Hn ( bp ) transgenic line. All taken together, it can be concluded that the mutation in Henna is responsible for drosopterin reduction in mutant Hn ( bp ), which provides key in vivo evidence to support the hypothesis that Henna is involved in drosopterin synthesis.

Red Green Colour Blindness among the Lingayath of Karnataka

A study of defective colour vision was carried out in 350 unrelated Lingayath individuals of both the sexes. It was found that the percentage frequency of red green colour blindness was 2.4%.

Quality evaluation of pickling cucumbers using hyperspectral reflectance and transmittance imaging—Part II. Performance of a prototype

This article reports on the development of a hyperspectral imaging prototype for online evaluation of external and internal quality of pickling cucumbers. The prototype consisted of a two-lane round belt conveyor, two illumination sources (one for reflectance and one for transmittance), and a hyperspectral imaging unit. It had a novel feature of simultaneous imaging under reflectance mode in the visible region (400–675 nm) and transmittance mode for the red and near-infrared region (Red-NIR) (675–1000 nm). Reflectance information from the visible region was intended for evaluating the external characteristics of cucumbers such as skin color, whereas transmittance information from Red-NIR was used for internal defect detection (i.e., hollow center). Additional features of the prototype included simultaneous acquisition of reflectance and transmittance from calibration references that were installed in the system, to provide real-time, continuous corrections of individual hyperspectral images from each sample. Methods and algorithms were developed of estimating cucumber fruit size and correcting the effect of fruit size on transmittance measurements. The system was calibrated and evaluated for detecting the color, size, and internal defect of pickling cucumbers.

Rayleigh matches in carriers of inherited color vision defects: The contribution from the third L/M photopigment

The mother or daughter of a male with an X-chromosome-linked red/green color defect is an obligate carrier of the color deficient gene array. According to the Lyonization hypothesis, a female carrier's defective gene is expressed and thus carriers may have more than two types of pigments in the L/M photopigment range. An open question is how a carrier's third cone pigment in the L/M range affects the postreceptoral neural signals encoding color. Here, a model considered how the signal from the third pigment pools with signals from the normal's two pigments in the L/M range. Three alternative assumptions were considered for the signal from the third cone pigment: it pools with the signal from (1) L cones, (2) M cones, or (3) both types of cones. Spectral-sensitivity peak, optical density, and the relative number of each cone type were factors in the model. The model showed that differences in Rayleigh matches among carriers can be due to individual differences in the number of the third type of L/M cone, and the spectral sensitivity peak and optical density of the third L/M pigment; surprisingly, however, individual differences in the cone ratio of the other two cone types (one L and the other M) did not affect the match. The predicted matches were compared to Schmidt's (1934/1955) report of carriers' Rayleigh matches. For carriers of either protanomaly or deuteranomaly, these matches were not consistent with the signal from the third L/M pigment combining with only the signal from M cones. The matches could be accounted for by pooling the third-pigment's response with L-cone signals, either exclusively or randomly with M-cone responses as well.

Protanomaly without darkened red is deuteranopia with rods

The Rayleigh match, a color match between a mixture of 545 + 670 nm lights and 589 nm light in modern instruments, is the definitive measurement for the diagnosis of inherited red–green color defects. All trichromats, whether normal or anomalous, have a limited range of 545 + 670 nm mixtures they perceive to match 589 nm: a typical color-normal match range is about 50–55% of 670 nm in the mixture (deutan mode), while deuteranomals have a range that includes mixtures with less 670 nm than normal and protanomals a range that includes mixtures with more 670 nm than normal. Further, the matching luminance of the 589 nm light for deuteranomals is the same as for normals but for protanomals is below normal. An example of an unexpected Rayleigh match, therefore, is a match range above normal (typical of protanomaly) and a normal luminance setting for 589 nm (typical of deuteranomaly), a match called protanomaly “when the red end of the spectrum is not darkened” [Pickford, R.W. (1950). Three pedigrees for color blindness. Nature, 165, 182.]. In this case, Rayleigh matching does not yield a clear diagnosis. Aside from Pickford, we are aware of only one other report of a similar observer [Pokorny, J., & Smith, V. C. (1981). A variant of red–green color defect. Vision Research, 21, 311–317]; this study predated modern genetic techniques that can reveal the cone photopigment(s) in the red–green range. We recently had the opportunity to conduct genetic and psychophysical tests on such an observer. Genetic results predict he is a deuteranope. His Rayleigh match is consistent with L cones and a contribution from rods. Further, with a rod-suppressing background, his Rayleigh match is characteristic of a single L-cone photopigment (deuteranopia).

Thermal, optical and spectroscopic assessment of Y b 3+ : NaY (MoO 4) 2 single crystal as a potential diode pumped laser near 1.04 μm

Large crystals of pure and Y b 3+ doped NaY (MoO 4) 2 have been grown using the Czochralski method. The major problem with these crystals is that they are black in colour, causeing total absorption in the visible range, this was resolved by annealing and the nature of the colour defect was discussed. Measurements such as DTA, thermal expansion in different crystallographic directions, and refractive index as a function of wavelength were investigated. The broad absorption band at about 980 nm and high value of the absorption cross-section are obtained for the Y b 3+ doped crystal. The results show that Y b 3+:NaY (MoO 4) 2 crystal has potential as a promising laser crystal.

Stem Cell Factor Functions as an Outgrowth-Promoting Factor to Enable Axon Exit from the Midline Intermediate Target

Commissural axons are attracted to the midline intermediate target by chemoattractants, but upon crossing the midline they switch off responsiveness to attractants and switch on responsiveness to midline repellents, which expel the axons from the midline and enable them to move on. Here we show that midline exit also requires the stimulation of axon outgrowth by Stem Cell Factor (SCF, also known as Steel Factor). SCF is expressed by midline floor plate cells, and its receptor Kit, a receptor tyrosine kinase, is expressed by commissural axons. In Steel and Kit mutant mice, the majority of commissural axons line up transiently at the contralateral edge of the floor plate, showing a delay in midline exit. In vitro, SCF selectively promotes outgrowth of postcrossing, but not precrossing, commissural axons. Our findings identify SCF as a guidance cue in the CNS, and provide evidence that exiting intermediate targets requires activation of outgrowth-promoting mechanisms.

Disturbed perception of colours associated with localized cerebral lesions. By J. C. Meadows (From the National Hospital for Nervous Diseases, Queen Square, London WCIN 3BG) Brain 1974: 97; 615-632.

Acquired cerebral achromatopsia is, at best, rare and its existence denied altogether by many authorities: thus Sir Gordon Holmes writing in 1918 and basing his views on ‘a very large number of cases’ considered that ‘isolated loss or dissociation of colour vision is not produced by cerebral lesions’. John Meadows aims to draw attention to evidence that bilateral but relatively discrete brain lesions may in fact lead to impaired colour vision. In discussing patients with acquired cerebral achromatopsia, his focus is on loss or impairment of the ability to distinguish hues or perceive the brightness of colours. For affected individuals, the world is grey and some may struggle with everyday activities through their inability to distinguish colours. But confusion has crept into the literature as a result of failure to distinguish the symptom of colour loss from abnormalities found only on formal testing; inability to name rather than perceive colour; situations in which the relevance of colour for interpreting the nature of an object or scene is lost; and failure to recognize that lesions of the anterior visual pathway may result in selective loss of acuity for colour compared with a white target. Starting with the case of McKay and Dunlop (The cerebral lesions in a case of complete acquired colour-blindness. Scot Med Surg J 1899; 5: 503–12), and accepting 14 other examples, Dr Meadows extracts the subtleties of the patients’ descriptions, often verbatim, that allow the distinction between cerebral achromatopsia and defective colour vision better explained by one or other of the ambiguities already listed. Thus, Bodamer's patient—‘speaking’ in 1947—describes everything as black and white as if sitting in the cinema: and Pallis's case feels that ‘my shirts all look dirty … I have no idea what tie to wear … I can tell peas and bananas only by …

Influence of saw and secateur pruning on stem discolouration, wound cicatrisation and diameter growth of Betula pendula

The aim of this case study was to compare the impacts of saw and secateur pruning on silver birch (Betula pendula Roth). Data were collected from two saw pruned stands in 2005, and one secateur pruned stand in 2003. All the stands were located in southern Finland. The sample stems were felled, and their butt logs were sawn into flitches, whose knot features and colour defects were measured. In addition, discs were sawn from each stem in order to study the annual ring widths. In this material, pruning with secateurs appeared to cause less colour defects than pruning with a saw. Irrespective of the pruning method used, the colour defects in the stem wood were at their largest in cases where the basal knob or the stem bark appeared to be damaged by pruning. Colour defects spread mainly towards the pith, only in a few cases towards the stem surface. The cicatrisation time of the knots as well as the length of the bark stick remaining inside the stem did not show significant differences between the two pruning methods. Pruning of the lowest living branches appears to have no effect on the diameter growth of silver birch trees.

Albinism and Leucism Among European Viperinae: a Review

The records of albino, partial albino, and leucistic individuals among four species of European Viperinae ( Vipera ammodytes , Vipera aspis , Vipera seoanei , and Vipera berus ) were summarized based on literature records, museum material, reports of field herpetologists and herpetoculturists, and a short description of all reported specimens was made. For the first three species only scattered observations have been made (1, 1, and 6 reports), whereas at Vipera berus these defects proved to be more widespread (16 reports), and present an occurrence pattern shift to the Nordic countries. Different hypotheses are postulated on the offset geographic distribution pattern of albinism and leucism at this species, taking into account the differences in predation pressure and population densities between populations in Southern and Northern Europe. The possible negative effect of the color defects on the fitness and survival of the specimens carrying them is debated.

Features Extraction for Eggplant Fruit Grading System Using Machine Vision

Machine vision based grading for agricultural crops has been well developed and accepted as an attractive grading method. However, machine vision based grading for eggplant fruit is not available yet. This study reports on the attempt to develop an eggplant grading machine using six CCD cameras as the sensing device. Feature extraction algorithms were developed to extract eggplant's features, i.e., length, diameter, volume, curvature, color homogeneity, calyx color, calyx area, and surface defect. The system could acquire six images per fruits covering the entire surface of the eggplant fruits. An agreement rate of 78.0% was achieved in the feasibility study where the machine vision based grading was compared with manual grading. The throughput of the developed system was 0.3 second per fruit. Details of the system, an outline of the algorithm, and performance results are reported in this article.

Diagnostic impact of SPECT image display on assessment of obstructive coronary artery disease

Diagnostic assessment of myocardial perfusion impacts the management of patients with suspected coronary artery disease (CAD). Although various image displays are available for single photon emission computed tomography (SPECT) interpretation, the effects of display differences on SPECT interpretation remain undetermined. We studied 183 patients undergoing SPECT, including 131 consecutive patients referred for angiography and 52 at low CAD risk. Studies were visually interpreted by use of color and gray images, with readers blinded to the results of the other display. In accordance with established criteria, a summed stress score (SSS) of 4 or greater was considered abnormal. The prevalence of abnormal SPECT findings was higher with gray images than with color images (54% vs 48%, P < .001) based on a uniform criterion (SSS > or =4). However, color images yielded equivalent sensitivity (79% vs 82%, P = .7) and improved specificity for global (50% vs 33%, P = .02) and vessel-specific CAD involving the right coronary artery (P < .01) and left anterior descending artery (P < .05). When the criterion for gray images was adjusted upward (SSS > or =5) to reflect increased mean defect severity (SSS of 5.1 vs 4.4, P = .01), gray and color images provided equivalent sensitivity and specificity for global and vessel-specific CAD. SPECT interpretation can vary according to image display as a result of differences in perfusion defect severity. Adjustment of abnormality criteria for gray images to reflect minor increases in defect severity provides equivalent diagnostic performance of gray and color displays for CAD assessment.

The Canon of Potato Science: 47. After-cooking Darkening

Potato after-cooking darkening (ACD) is a tuber colour defect that occurs after cooking, including boiling, baking, frying or dehydration. The dark colour ranges from light grey to almost black, depending on cultivar. The development of the colour is caused by a non-enzymatic oxidation process during cooking, and reaches its maximum level in about 2 h after cooking is completed. After-cooking darkening is one of the most widespread and undesirable characteristics of cultivated potato. Although it does not affect the flavour or nutritional value of the potatoes, the dark colour significantly affects the appearance of products. After-cooking darkening is caused by the oxidation reaction of the ferrouschlorogenic acid complex, resulting in a bluish-grey compound ferri-dichlorogenic acid. It is suggested that tubers with higher concentration of chlorogenic acid show higher degree of ACD. Therefore these tubers have higher susceptibility to ACD. Although iron (Fe) is involved in the reaction, its concentration does not determine the degree of ACD in tubers. However, iron chelating agents, such as citric acid, ascorbic acid, malete, phosphate, and EDTA, can decrease the degree of ACD by preventing the iron to react with chlorogenic acid. The degree of the darkness in a tuber is not evenly distributed: it is always higher at the stem end and in the cortex tissue just under the skin, and lower at the bud end and the central location of the tuber. After-cooking darkening is a quantitative trait that is predominantly controlled by genetic factors. Therefore, it is cultivar dependent. Other tuber quality traits, such as skin colour, flesh colour, specific gravity and frying colour, are not related to ACD. Potato Research (2007) 50:403–406 DOI 10.1007/s11540-008-9061-x

Luminance contrast with clear and yellow-tinted intraocular lenses

To determine whether yellow-tinted intraocular lenses (IOLs) negatively affect luminance contrast in postoperative cataract patients. Department of Ophthalmology, Sir Mortimer B. Davis Jewish General Hospital, McGill University, Montreal, Quebec, Canada. Luminance contrast was measured using the minimum-motion technique. The stimulus consisted of blue and red sinusoidal gratings differing in luminance. Patients had implantation of a clear or yellow-tinted IOL and were tested monocularly 2 to 9 weeks after cataract surgery. No patient had concomitant ocular diseases or congenital color defects, assessed by their ophthalmologist, or flicker-sensitive epilepsy. All patients had a visual acuity of 20/40 or better a mean of 4 weeks+/-2 (SD) postoperatively. Patients ranged in age from 55 to 89 years. An independent-samples Student t test showed that patients with a yellow-tinted IOL had significantly lower luminance contrast values than patients with a clear IOL (P<.05). The results suggest that yellow-tinted IOLs affect the perception of luminance under photopic conditions. More blue light was required to make luminance judgments with a yellow-tinted IOL than with a clear IOL. Further study of the functional impact of luminance reduction by yellow-tinted IOLs is warranted.

Red-Green Color Vision Impairment in Duchenne Muscular Dystrophy

The present study evaluated the color vision of 44 patients with Duchenne muscular dystrophy (DMD) (mean age 14.8 years; SD 4.9) who were submitted to a battery of four different color tests: Cambridge Colour Test (CCT), Neitz Anomaloscope, Ishihara, and American Optical Hardy-Rand-Rittler (AO H-R-R). Patients were divided into two groups according to the region of deletion in the dystrophin gene: upstream of exon 30 (n=12) and downstream of exon 30 (n=32). The control group was composed of 70 age-matched healthy male subjects with no ophthalmological complaints. Of the patients with DMD, 47% (21/44) had a red-green color vision defect in the CCT, confirmed by the Neitz Anomaloscope with statistical agreement (P<.001). The Ishihara and the AO H-R-R had a lower capacity to detect color defects--5% and 7%, respectively, with no statistical similarity between the results of these two tests nor between CCT and Anomaloscope results (P>.05). Of the patients with deletion downstream of exon 30, 66% had a red-green color defect. No color defect was found in the patients with deletion upstream of exon 30. A negative correlation between the color thresholds and age was found for the controls and patients with DMD, suggesting a nonprogressive color defect. The percentage (66%) of patients with a red-green defect was significantly higher than the expected <10% for the normal male population (P<.001). In contrast, patients with DMD with deletion upstream of exon 30 had normal color vision. This color defect might be partially explained by a retina impairment related to dystrophin isoform Dp260.

Identifying constituents of whey protein concentrates that reduce the pink color defect in cooked ground turkey

Whey protein concentrate constituents were tested for their ability to reduce naturally occurring pink color defect and pink cooked color induced by sodium nitrite (10 ppm) and nicotinamide (1.0%) in ground turkey. β-lactoglobulin (1.8%), α-lactalbumin (0.8%), bovine serum albumin (0.15–0.3%), lactose (1.0–3.0%), potassium chloride (500–1500 ppm), and ferrous iron chloride (0.3–30 ppm) had no effects on cooked pink color. Lactoferrin (30–5000 ppm) increased or decreased pink color depending on its concentration in samples without added sodium nitrite or nicotinamide. Annatto (0.1–1.0 ppm) reduced pink color whereas the higher concentration of magnesium chloride (22–88 ppm) and ferric iron chloride (0.3–30 ppm) increased pink color in samples with added nicotinamide. Calcium chloride (160–480 ppm) was the only tested constituent that consistently reduced pink cooked color in samples with and without added nitrite and nicotinamide. Due to the variability of whey protein concentrates and the number of constituents that do not reduce pink cooked color, the addition of calcium alone or dried milk minerals containing calcium, phosphate, and citrate, represents a better means to regularly prevent the pink color defect in cooked ground turkey.

Calcium chloride and tricalcium phosphate effects on the pink color defect in cooked ground and intact turkey breast

Calcium chloride (250, 500 ppm) was examined for its ability to reduce the pink color defect induced by sodium nitrite (10 ppm) and nicotinamide (1.0%) in cooked ground turkey in the presence and absence of sodium tripolyphosphate (0.25, 0.5%) and sodium citrate (0.5, 1.0%). The ability of tricalcium phosphate (0.1–0.5%) to reduce pink cooked color also was evaluated in ground turkey and both calcium chloride and tricalcium phosphate were tested for their effects on pink cooked color in whole breast muscle. The combination of calcium chloride and sodium tripolyphosphate, not calcium chloride alone, was necessary for a reduction in pink cooked color induced by nicotinamide. Subsequently, in the presence of phosphate, both calcium chloride and sodium citrate reduced pink cooked color and were most effective in combination. Tricalcium phosphate also was capable of reducing pink cooked color in ground turkey, however substituting tricalcium phosphate for sodium tripolyphosphate resulted in lower pH and cooking yields. Neither calcium chloride nor tricalcium phosphate was capable of reducing pink cooked color in whole turkey breast. Currently, a combination of sodium tripolyphosphate, calcium chloride, and sodium citrate represents the most suitable means for reducing or preventing the pink color defect in uncured ground turkey.

UV-vis absorption of the transition metal-doped SiO 2–B 2O 3–Na 2O glasses

Ultravoilet (UV)–vis absorption spectra of undoped and transition metal (TM)-doped borosilicate glasses before and after successive gamma rays irradiation are reported. Before irradiation, the undoped glass reveals UV absorption due to trace iron impurities and no visible bands whereas the TM-doped glasses show the absorption bands which are characteristic for each TM ion in the UV and visible regions. The induced absorption bands are examined and related to either intrinsic radiation-induced defects from the host base borosilicate glass or extrinsic induced defects generated from TMs. The response of the glasses to gamma irradiation is related to the creation of defect color centers, the approach of a saturation condition and/or the possible photochemical effect on TM.