Effects of age and optical blur on real depth stereoacuity

Stereoscopic depth perception utilizes the disparity cues between the images that fall on the retinae of the two eyes. The purpose of this study was to determine what role aging and optical blur play in stereoscopic disparity sensitivity for real depth stimuli. Forty-six volunteers were tested ranging in age from 15 to 60 years. Crossed and uncrossed disparity thresholds were measured using white light under conditions of best optical correction. The uncrossed disparity thresholds were also measured with optical blur (from +1.0D to +5.0D added to the best correction). Stereothresholds were measured using the Frisby Stereo Test, which utilizes a four-alternative forced-choice staircase procedure. The threshold disparities measured for young adults were frequently lower than 10 arcsec, a value considerably lower than the clinical estimates commonly obtained using Random Dot Stereograms (20 arcsec) or Titmus Fly Test (40 arcsec) tests. Contrary to previous reports, disparity thresholds increased between the ages of 31 and 45 years. This finding should be taken into account in clinical evaluation of visual function of older patients. Optical blur degrades visual acuity and stereoacuity similarly under white-light conditions, indicating that both functions are affected proportionally by optical defocus.

Color vision impairment in type 2 diabetes assessed by the D-15d test and the Cambridge Colour Test

Color vision impairment emerges at early stages of diabetes mellitus type 2 (DM2) and may precede diabetic retinopathy or the appearance of vascular alterations in the retina. The aim of the present study was to compare the evaluation of the color vision with two different tests - the Lanthony desaturated D-15d test (a traditional color arrangement test), and the Cambridge Colour Test (CCT) (a computerized color discrimination test) - in patients diagnosed with DM2 without clinical signs of diabetic retinopathy (DR), and in sex- and age-matched control groups. Both color tests revealed statistically significant differences between the controls and the worst eyes of the DM2 patients. In addition, the degree of color vision impairment diagnosed by both tests correlated with the disease duration. The D-15d outcomes indicated solely tritan losses. In comparison, CCT outcomes revealed diffuse losses in color discrimination: 13.3% for best eyes and 29% for worst eyes. In addition, elevation of tritan thresholds in the DM2 patients, as detected by the Trivector subtest of the CCT, was found to correlate with the level of glycated hemoglobin. Outcomes of both tests confirm that subclinical losses of color vision are present in DM2 patients at an early stage of the disease, prior to signs of retinopathy. Considering the advantages of the CCT test compared to the D-15d test, further studies should attempt to verify and/or improve the efficiency of the CCT test.

Color-space distortions following long-term occupational exposure to mercury vapor

Color vision was examined in subjects with long-term occupational exposure to mercury (Hg) vapor. The color vision impairment was assessed by employing a quantitative measure of distortion of individual and group perceptual color spaces. Hg subjects (n = 18; 42.1 +/- 6.5 years old; exposure time = 10.4 +/- 5.0 years; time away from the exposure source = 6.8 +/- 4.6 years) and controls (n = 18; 46.1 +/- 8.4 years old) were examined using two arrangement tests, D-15 and D-15d, in the traditional way, and also in a triadic procedure. From each subject`s `odd-one-out` choices, matrices of inter-cap subjective dissimilarities were derived and processed by non-metric multidimensional scaling (MDS). D-15d results differed significantly between the Hg-group and the control group (p < 0.05), with the impairment predominantly along the tritan axis. 2D perceptual color spaces, individual and group, were reconstructed, with the dimensions interpreted as the red-green (RG) and the blue-yellow (BY) systems. When color configurations from the Hg-group were compared to those of the controls, they presented more fluctuations along both chromatic dimensions, indicating a statistically significant difference along the BY axis. In conclusion, the present findings confirm that color vision impairments persist in subjects that have received long-term occupational exposure to Hg-vapor although, at the time of testing, they were presenting mean urinary concentration within the normal range for non-exposed individuals. Considering the advantages of the triadic procedure in clinical evaluation of acquired color vision deficiencies, further studies should attempt to verify and/or improve its efficacy.

A computer-controlled color vision test for children based on the Cambridge Colour Test

The present study aimed at providing conditions for the assessment of color discrimination in children using a modified version of the Cambridge Colour Test (CCT, Cambridge Research Systems Ltd., Rochester, UK). Since the task of indicating the gap of the Landolt C used in that test proved counterintuitive and/or difficult for young children to understand, we changed the target Stimulus to a patch of color approximately the size of the Landolt C gap (about 7 degrees Of Visual angle at 50 cm from the monitor). The modifications were performed for the CCT Trivector test which measures color discrimination for the protan, deutan and tritan confusion lines. Experiment I Sought to evaluate the correspondence between the CCT and the child-friendly adaptation with adult subjects (n = 29) with normal color vision. Results showed good agreement between the two test versions. Experiment 2 tested the child-friendly software with children 2 to 7 years old (n = 25) using operant training techniques for establishing and maintaining the subjects` performance. Color discrimination thresholds were progressively lower as age increased within the age range tested (2 to 30 years old), and the data-including those obtained for children-fell within the range of thresholds previously obtained for adults with the CCT. The protan and deutan thresholds were consistently lower than tritan thresholds, a pattern repeatedly observed in adults tested with the CCT. The results demonstrate that the test is fit for assessment of color discrimination in young children and may be a useful tool for the establishment of color vision thresholds during development.

Irreversible color vision losses in patients with chronic mercury vapor intoxication

This longitudinal study addresses the reversibility of color vision losses in subjects who had been occupationally exposed to mercury vapor. Color discrimination was assessed in 20 Hg-exposed patients (mean age = 42.4 +/- 6.5 years; 6 females and 14 males) with exposure to Hg vapor during 10.5 +/- 5.3 years and away from the work place (relative to 2002) for 6.8 +/- 4.2 years. During the Hg exposure or up to one year after ceasing it, mean urinary Hg concentration was 47 +/- 35.4 mu g/g creatinine. There was no information on Hg urinary concentration at the time of the first tests, in 2002 (Ventura et al., 2005), but at the time of the follow-up tests, in 2005, this value was 1.4 +/- 1.4 mu g/g creatinine for patients compared with 0.5 +/- 0.5 mu g/g creatinine for controls (different group from the one in Ventura et al. (2005)). Color vision was monocularly assessed using the Cambridge Colour Test (CCT). Hg-exposed patients had significantly worse color discrimination (p < 0.02) than controls, as evaluated by the size of MacAdam`s color discrimination ellipses and color discrimination thresholds along protan, deutan, and tritan confusion axes. There were no significant differences between the results of the study in Ventura et al. (2005) and in the present follow-up measurements, in 2005, except for worsening of the tritan thresholds in the best eye in 2005. Both chromatic systems, blue-yellow and red-green, were affected in the first evaluation (Ventura et al., 2005) and remained impaired in the follow-up testing, in 2005. These findings indicate that following a long-term occupational exposure to Hg vapor, even several years away from the source of intoxication, color vision impairment remains irreversible.

Characterization of Opsin Gene Alleles Affecting Color Vision in a Wild Population of Titi Monkeys (Callicebus brunneus)

The color vision of most platyrrhine primates is determined by alleles at the polymorphic X-linked locus coding for the opsin responsible for the middle- to long-wavelength (M/L) cone photopigment. Females who are heterozygous at the locus have trichromatic vision, whereas homozygous females and all males are dichromatic. This study characterized the opsin alleles in a wild population of the socially monogamous platyrrhine monkey Callicebus brunneus (the brown titi monkey), a primate that an earlier study suggests may possess an unusual number of alleles at this locus and thus may be a subject of special interest in the study of primate color vision. Direct sequencing of regions of the M/L opsin gene using feces-, blood-, and saliva-derived DNA obtained from 14 individuals yielded evidence for the presence of three functionally distinct alleles, corresponding to the most common M/L photopigment variants inferred from a physiological study of cone spectral sensitivity in captive Callicebus. Am. J. Primatol. 73:189-196, 2011. (C) 2010 Wiley-Liss, Inc.

Color texture analysis based on fractal descriptors

Color texture classification is an important step in image segmentation and recognition. The color information is especially important in textures of natural scenes, such as leaves surfaces, terrains models, etc. In this paper, we propose a novel approach based on the fractal dimension for color texture analysis. The proposed approach investigates the complexity in R, G and B color channels to characterize a texture sample. We also propose to study all channels in combination, taking into consideration the correlations between them. Both these approaches use the volumetric version of the Bouligand-Minkowski Fractal Dimension method. The results show a advantage of the proposed method over other color texture analysis methods. (C) 2011 Elsevier Ltd. All rights reserved.

Color tunability of intense upconversion emission from Er3+-Yb3+ co-doped SiO2-Ta2O5 glass ceramic planar waveguides

This work reports on the infrared-to-visible CW frequency upconversion from planar waveguides based on Er3+-Yb3+-doped 100-xSiO(2)-xTa(2)O(5) obtained by a sol-gel process and deposited onto a SiO2-Si substrate by dip-coating. Surface morphology and optical parameters of the planar waveguides were analyzed by atomic force microscopy and the m-line technique. The influence of the composition on the electronic properties of the glass-ceramic films was followed by the band gap ranging from 4.35 to 4.51 eV upon modification of the Ta2O5 content. Intense green and red emissions were detected from the upconversion process for all the samples after excitation at 980 nm. The relative intensities of the emission bands around 550 nm and 665 nm, assigned to the H-2(11/2) -> I-4(15/2), S-4(3/2) -> I-4(15/2), and F-4(9/2) -> I-4(15/2) transitions, depended on the tantalum oxide content and the power of the laser source at 980 nm. The upconversion dynamics were investigated as a function of the Ta2O5 content and the number of photons involved in each emission process. Based on the upconversion emission spectra and 1931CIE chromaticity diagram, it is shown that color can be tailored by composition and pump power. The glass ceramic films are attractive materials for application in upconversion lasers and near infrared-to-visible upconverters in solar cells.

Nonlinear (magnetic) correction to the field of a static charge in an external field

We find the first nonlinear correction to the field produced by a static charge at rest in a background constant magnetic field. It is quadratic in the charge and purely magnetic. The third-rank polarization tensor-the nonlinear response function-is written within the local approximation of the effective action in an otherwise model-and approximation-independent way within any P-invariant nonlinear electrodynamics, QED included. DOI: 10.1103/PhysRevD.86.125028

Color stability, surface roughness and microhardness of composites submitted to mouthrinsing action

Objective: The purpose of this study was to evaluate the effect of mouth rinse solutions Lion color stability, surface roughness and microhardness of two composite resins. Material and Methods: Fifty test specimens of each composite (Filtek Z250 and Z350; 3M ESPE) were made using a teflon matrix (12x2 mm). Color, surface roughness and Knoop microhardness baseline measurements of each specimen were made and specimens (n=10) were immersed in 5 mouth rinse solutions: G1: distilled water (control), G2: Plax Classic, G3: Plax alcohol-free; G4: Periogard, and G5: Listerine. Final measurements of color, roughness and microhardness were performed and the results submitted to statistical analysis (2-way ANOVA, Bonferroni's test; p<0.05). Results: The most significant color change was observed for Z250 when immersed in Listerine (p<0.05). Z350 showed greater color change when immersed in Plax alcohol-free (p<0.05), but with no significant difference for Listerine (p>0.05). With regard to roughness, both composites showed significant changes when immersed in Listerine in comparison with Plax alcohol-free (p<0.05). Microhardness of Z350 was shown to be significantly changed when the composite was immersed in Plax alcohol-free (p<0.05). Conclusion: Composite changes depended on the material itself rather than the mouth rinse solution used.

Outcomes of correction of internal hip rotation in patients with spastic cerebral palsy using proximal femoral osteotomy

Internal hip rotation (IHR) is the major cause of intoeing gait in patients with cerebral palsy (CP). Femoral derotation osteotomy (FDO) is the preferred treatment to correct excessive anteversion, however the condition may persist or recur postoperatively. Retrospective clinical and kinematic evaluation of 75 spastic diplegic CP patients was conducted for a mean duration of 22 months following proximal FDO. The patients were divided into two groups depending on the correction or persistence of IHR evident at kinematics after surgery. If corrected, mean patient follow-up was extended to 53 months. Outcomes were analyzed using Two Proportions Equality, Mann-Whitney and Wilcoxon tests. IHR persisted in 33.3% of cases at mean follow-up of 22 months and subtrochanteric femur osteotomy was more frequent in this group (p = 0.033). Thirty-five of the fifty-four patients with first-round gait correction were monitored during the extended follow-up. Those for whom IHR recurred (9.5%) had undergone FDO at a comparatively younger age. Patient gender, operations prior to or at the time of femoral osteotomy, topographic classification, GMFCS level, or the extent of preoperative clinical and kinematic abnormalities had no apparent influence on persistence or recurrence of abnormal gait. (C) 2012 Elsevier B.V. All rights reserved.

Using the Hard, Randy, and Rittler Test to Evaluate Color Vision in Capuchins (Cebus libidinosus)

The identification of color vision types in primates is fundamental to understanding the evolution and biological function of color perception. The Hard, Randy, and Rittler (HRR) pseudoisochromatic test categorizes human color vision types successfully. Here we provide an experimental setup to employ HRR in a nonhuman primate, the capuchin (Cebus libidinosus), a platyrrhine with polymorphic color vision. The HRR test consists of plates with a matrix composed of gray circles that vary in size and brightness. Differently colored circles form a geometric shape (X, O, or Delta) that is discriminated visually from the gray background pattern. The ability to identify these shapes determines the type of dyschromatopsy (deficiency in color vision). We tested six capuchins in their own cages under natural sunlight. The subjects chose between two HRR plates in each trial: one with the gray pattern only and the other with a colored shape, presented on the left or right side at random. We presented the test 40 times and calculated the 95 % confidence limits for chance performance based on the binomial test. We also genotyped all subjects for exons 3 and 5 of the X-linked opsin genes. The HRR test diagnosed two subjects as protan dichromats (missing or defective L-cone), three as deutan dichromats (missing or defective M-cone), and one female as trichromat. Genetic analysis supported the behavioral data for all subjects. These findings show that the HRR test can be applied to diagnose color vision in nonhuman primates.

Correction of Severe Ptosis with a Silicone Implant Suspensor: 22 Years of Experience

Background: Patients with severe ptosis caused by poor or absent function of the levator muscle but with good frontalis muscle excursion usually benefit from a frontalis sling procedure. This is currently carried out using organic or inorganic material to connect the upper eyelid to the frontalis muscle. Methods: The aim of this study was to evaluate retrospectively 112 patients who underwent frontalis sling procedures between 1989 and 2011 using a preformed silicone implant suspensor to correct severe ptosis. Results: The results obtained using this technique were good or fair in 95.54 percent of the cases and poor in 4.46 percent of the cases. The authors discuss the results of the study and the cases in which the procedure should be indicated and highlight the advantages of the method. Conclusion: The availability of this low-cost sterile device, together with the fact that it is ready to use, requires less invasive surgery, saves time, and is sufficiently versatile to allow adjustments to be made at any time, makes the silicone eyelid sling an attractive choice for correcting ptosis. (Plast. Reconstr. Surg. 129: 453e, 2012.)

Long-Term Occupational Exposure to Organic Solvents Affects Color Vision, Contrast Sensitivity and Visual Fields

The purpose of this study was to evaluate the visual outcome of chronic occupational exposure to a mixture of organic solvents by measuring color discrimination, achromatic contrast sensitivity and visual fields in a group of gas station workers. We tested 25 workers (20 males) and 25 controls with no history of chronic exposure to solvents (10 males). All participants had normal ophthalmologic exams. Subjects had worked in gas stations on an average of 9.6 +/- 6.2 years. Color vision was evaluated with the Lanthony D15d and Cambridge Colour Test (CCT). Visual field assessment consisted of white-on-white 24-2 automatic perimetry (Humphrey II-750i). Contrast sensitivity was measured for sinusoidal gratings of 0.2, 0.5, 1.0, 2.0, 5.0, 10.0 and 20.0 cycles per degree (cpd). Results from both groups were compared using the Mann-Whitney U test. The number of errors in the D15d was higher for workers relative to controls (p<0.01). Their CCT color discrimination thresholds were elevated compared to the control group along the protan, deutan and tritan confusion axes (p<0.01), and their ellipse area and ellipticity were higher (p<0.01). Genetic analysis of subjects with very elevated color discrimination thresholds excluded congenital causes for the visual losses. Automated perimetry thresholds showed elevation in the 9 degrees, 15 degrees and 21 degrees of eccentricity (p<0.01) and in MD and PSD indexes (p<0.01). Contrast sensitivity losses were found for all spatial frequencies measured (p<0.01) except for 0.5 cpd. Significant correlation was found between previous working years and deutan axis thresholds (rho = 0.59; p<0.05), indexes of the Lanthony D15d (rho = 0.52; p<0.05), perimetry results in the fovea (rho = -0.51; p<0.05) and at 3, 9 and 15 degrees of eccentricity (rho = -0.46; p<0.05). Extensive and diffuse visual changes were found, suggesting that specific occupational limits should be created.

Estimate of corrected values and the effect of correction for measurement error in dietary data obtained by the Food Frequency Questionnaire for Adolescents (AFFQ)

The scope of this study was to estimate calibrated values for dietary data obtained by the Food Frequency Questionnaire for Adolescents (FFQA) and illustrate the effect of this approach on food consumption data. The adolescents were assessed on two occasions, with an average interval of twelve months. In 2004, 393 adolescents participated, and 289 were then reassessed in 2005. Dietary data obtained by the FFQA were calibrated using the regression coefficients estimated from the average of two 24-hour recalls (24HR) of the subsample. The calibrated values were similar to the the 24HR reference measurement in the subsample. In 2004 and 2005 a significant difference was observed between the average consumption levels of the FFQA before and after calibration for all nutrients. With the use of calibrated data the proportion of schoolchildren who had fiber intake below the recommended level increased. Therefore, it is seen that calibrated data can be used to obtain adjusted associations due to reclassification of subjects within the predetermined categories.