Trichromatic critical flicker frequency as potential visual test in cataract and macula disease patients.

PURPOSE: To investigate the capacity of critical flicker frequency (CFF) in discriminating cataract eyes with or without macula disease using trichromatic flickers, and to develop a model to predict postoperative best corrected visual acuity (BCVA). METHODS: Patients were divided into two groups based on the presence or absence of macular disease. CFF threshold measurements of red (R-CFF), green (G-CFF), and yellow (Y-CFF) flickers were conducted both preoperatively and postoperatively. A generalized estimating equations model (GEE) was employed to examine the relationship between CFF threshold and 3-month postoperative BCVA. RESULTS: A total of 115 eyes were enrolled, with 59 eyes in the cataract alone group and 56 eyes in the cataract with macular disease group completing the follow-up. R-CFF was found to be consistent before and after cataract removal (P = 0.06), even in cases where OCT was not performed successfully (P > 0.05). Y-CFF showed the highest AUC (0.798) for differentiating ocular comorbidities. According to the GEE model, in patients with a CFF threshold below 26 Hz, the odds ratios for achieving a postoperative VA of 20/40 or better were 34.8% for R-CFF, 26.0% for G-CFF, and 24.5% for Y-CFF. CONCLUSION: CFF emerges as a promising tool for predicting postoperative BCVA, providing valuable supplementary insights when fundus examination is obstructed. R-CFF demonstrates the best resistance to cataracts, while Y-CFF exhibits the highest sensitivity both in identifying macular diseases and predicting postoperative BCVA of 20/40 or better.

Assessment of the perception of vertical subjectivity in children born preterm.

Children born preterm have increased rates of paediatric mortality and morbidity. Prematurity has been associated with impaired visual perception and visuo-motor integration. The alteration of the perception of verticality translates into alterations of the vestibular system at central and/or peripheral level, which may manifest itself in symptoms such as imbalance, dizziness or even vertigo. The aim of this study was to compare subjective visual vertical (SVV) test scores in children born preterm with those of children born at term at ages between 7 and 10. One hundred ten children with no neurodevelopmental disorder of 7 to 10 years of age were studied using a mobile application on a smartphone attached to a wall by means of a rotating plate. The SVV test was compared between two groups: a group of 55 preterm children (53 very preterm children born under 32 weeks of gestational age and 2 preterm with very low birth weight) and another group of 55 children born at term (after 37 weeks of gestational age). The SVV results were analysed for comparison with respect to prematurity, sex and age. We found no significant differences in the SVV study in the comparison between preterm and term children. In addition, no significant differences were observed regarding sex or age between 7 and 10 years.  Conclusion: We found no alterations in the perception of vertical subjectivity in children between 7 and 10 years of age, with antecedents of very preterm birth and/or very low birth weight. What is Known: • The different studies published so far suggest the existence of balance disorders in premature children, although in most of these studies the children are examined at an age when the vestibular system is not mature and with non-specific tests for the study of the vestibular system. What is New: • We compared the results of the subjective visual vertical (SVV) test in a group of 55 preterm children (53 very preterm children born under 32 weeks of gestational age and 2 preterm with very low weight at birth) and in a group of 55 children born at term (after 37 weeks of gestational age), at the ages of 7 to 10 years and observed no differences. • We conclude that, if there had been any vestibular alterations due to very premature birth, these must have been compensated by the age of 7.

Quantitative visual tests in primary open-angle glaucoma patients according to three different lights with different color-rendering index.

PURPOSE: To compare quantitative visual tests, such as visual acuity, contrast sensitivity, and color vision tests in patients with primary open-angle glaucoma (POAG) patients according to three different light systems with different color-rendering index (CRI). METHODS: This was a cross-sectional study of 36 eyes in 36 patients with POAG. Three different light systems consisting of a 3-band fluorescent lamp (CRI 80), a white LED (CRI 75), and a quantum dot LED (CRI > 95) were used. All lights had the same illuminance of 230 lx to exclude illuminance effects. The visual testing included best-corrected visual acuity (BCVA) using an ETDRS chart, a CSV-1000E contrast test, and a color test performed by the Farnsworth Munsell 100-hue test. RESULTS: There was no significant difference in BCVA (p = 0.86). There were no significant differences in the detail contrast tests according to the three light systems (p = 0.95, p = 0.94, p = 0.94, respectively, p = 0.64). There was significant difference between the three light systems in color test (p = 0.042). The color test scores with a quantum dot LED were significantly lower than those of the white LED and 3-band fluorescent lamp (p = 0.03 and 0.047, respectively). CONCLUSIONS: POAG patients did not show significant differences in visual acuity scores and contrast test scores, expressed as black and white symbols, according to the different light systems. However, POAG patients tested under a quantum dot LED (CRI > 95) could distinguish color differences better than in the other light systems.

Evaluation of a cattle rapid test for early pregnancy diagnosis in sheep.

The early pregnancy diagnosis allows optimizing production and timely management correction, with a greater reproductive output of livestock. The Idexx Rapid Visual Pregnancy Test® consists of an ELISA for visual reading which does not require the use of readers in the laboratory, with satisfactory pregnancy diagnoses at 28 days of pregnancy in cattle. Therefore, the aim of this study was to evaluate this rapid test and to verify the most appropriate day for the diagnosis of pregnancy in the ovine species. For this purpose, 98 serum samples from pregnant sheep and 36 from non-pregnant were used, with duplicate samples, and diagnosis was confirmed by ultrasound examination, used as the gold standard. The numbers of positive samples obtained at 26, 28, and 30 days of pregnancy were 26, 27, and 45, respectively. The Rapid Visual Pregnancy Test correctly identified 100% of the samples as positive at pregnancy of days 26, 28, and 30. The sensitivity and specificity of the test were also 100%. The Idexx Rapid Visual Pregnancy Test, initially indicated for cattle, is effective for the detection of pregnancy in the ovine species, enabling diagnosis of pregnant sheep from the 26th day of pregnancy.

A hairpin-type DNA probe for direct colorimetric detection of endonuclease activity and inhibition based on the deaggregation of gold nanoparticles.

A method is described for the determination of the activity of endonuclease. It based on the deaggregation of gold nanoparticles (AuNPs) aggregated by the action of poly(diallyldimethylammonium chloride) (PDDA). A single-stranded DNA (ssDNA) is released after enzymatic cleavage catalyzed by endonuclease. The released fragments bind electrostatically to PDDA and inhibit the PDDA-induced aggregation of AuNPs. This is accompanied by a color change from blue to red and a decrease in the absorption ratio (A630/A520). Under the optimal conditions, this ratio increases linearly in the 0.001 to 1 U·µL-1 EcoRI endonuclease activity range. The detection limit is of 2 × 10-4 U·µL-1 which is much better or at least comparable to previous reports. The method is deemed to have wide scope in that it may be used to study other endonuclease activity (such as BamHI) by simply changing the specific recognition site of the hairpin-like DNA probe. The assay may also be employed to screening for inhibitors of EcoRI endonuclease. Graphical abstract Schematic presentation of the colorimetric assay based on the deaggregation of AuNPs for the detection of endonuclease activity. A single-stranded sequence (ssDNA) is released by the EcoRI cleavage, which electrostatically binds to PDDA and inhibits the PDDA-induced aggregation of AuNPs accompanying with a color change from blue to red.

Ratiometric fluorometric determination of the anthrax biomarker 2,6-dipicolinic acid by using europium(III)-doped carbon dots in a test stripe.

Europium(III)-doped carbon dots (Eu-CDs) were prepared from citric acid and europium nitrate via a one-pot pyrolytic method. The Eu-CDs emit intense blue fluorescence (with excitation/emission peaks at 365/465 nm), are water soluble and biocompatible. On addition of 2,6-dipicolinic acid (DPA; an anthrax biomarker), ligand-to-ion energy transfer occurs from DPA to Eu(III) which has a red emission peaking at 615 nm. This results in an increase of the intensity of the red fluorescence. DPA can be detected by the ratio of fluorescence intensities at 616 and 475 nm. The method has an analytical range that extends from 5 to 700 nmol·L-1, with a 5 nmol·L-1 detection limit. The Eu-CDs also were incorporated into a test paper for visual detection of DPA with a portable UV lamp and a smartphone. In this case, the detection limit is 1 µmol·L-1. The Eu-CDs internalize well into HeLa cells, and this paves the way to bioimaging. Graphical abstract Schematic of a method for visual detection of 2,6-dipicolinic acid (DPA, an anthrax biomarker) by using a test stripe impregnated with europium(III)-doped carbon dots (Eu-CDs).

A pregnancy test strip for detection of pathogenic bacteria by using concanavalin A-human chorionic gonadotropin-Cu3(PO4)2 hybrid nanoflowers, magnetic separation, and smartphone readout.

Pregnancy test strips are widely used in daily life. A commercial pregnancy test strip was modified to obtain a point-of-care device for the detection of pathogenic bacteria. Hybrid nanoflowers were prepared from concanavalin A, human chorionic gonadotropin, and Cu3(PO4)2 via a one-pot method. They were used as signaling probes in an off-the-shelf pregnancy test strip. This modified lateral flow immunoassay can detect Escherichia coli O157:H7 with a detection limit of 4 CFU·mL-1, and Salmonella typhimurium with a detection limit of 3 CFU·mL-1. Conceivably, the method has high potential as a portable and cost-effective tool for rapid determination of a wide range of analytes, especially in resource-constrained settings. Graphical abstract Hybrid nanoflower loaded human chorionic gonadotropin (hCG) and concanavalin A (hCG - nanoflowers) were synthesized via a one-pot method and used as signal labels with commercial commercial-off-the-shelf pregnancy test strips to detect pathogenic bacteria targets, thus yielding an easily smartphone readout signal.

Gold nanoparticle-based colorimetric ELISA for quantification of ractopamine.

The work describes a gold nanoparticle-based colorimetric enzyme-linked immunosorbent assay (ELISA) for ractopamine. The ELISA is based on an indirect competitive approach. In the presence of ractopamine, gold(III) ions are oxidized by H2O2 to form red AuNPs. On the other hand, the AuNP in solution are purple-blue due to aggregation if the sample does not contain ractopamine. The absorption, best measured at 560 nm, increases linearly in the 2 to 512 ng·mL-1 ractopamine concentration range, and the detection limit is as low as 0.35 ng·mL-1 in urine. Ractopamine can also be detected visually, even in the presence of other ß-agonists and antibiotics. The results obtained by this method are consistent with those obtained by LC-MS/MS as demonstrated by analysis of sheep urine. The ELISA method described here is inexpensive, easy-to-use, and suitable for rapid screening of ractopamine in animal samples. Graphical abstract Schematic presentation of a colorimetric indirect competitive immunoassay for ractopamine. It is based on the use of catalase labeled IgG and the measurement of the absorption of red gold nanoparticles (AuNPs) that are generated by the reaction of gold ions with H2O2. In the absence of ractopamine, the solution becomes blue.

Glucose oxidase assisted visual detection of glucose using oxygen deficient α-MoO3-x nanoflakes.

An optical method is described for the quantitation of glucose by using oxygen-deficient α-MoO3-x nanoflakes. It is based on the use of glucose oxidase (GOx) which produces hydrogen peroxide on oxidation of glucose. Hydrogen peroxide then oxidizes the α-MoO3-x nanoflakes, and this results in a visible color change from blue to colorless. The color change can be measured photometrically at 740 nm. The method has a 68 nM detection limit. Graphical Abstract Mechanism of glucose detection using blue colored oxygen deficient 2D α-MoO3-x nanoflakes. Hydrogen peroxide (H2O2) is formed as a by-product in the conversion of glucose to glucono-1,5-lactone by glucose oxidase (GOx). In the presence of H2O2, the oxygen vacancies in α-MoO3-x nanoflakes are filled up, and this leads to the loss of blue color of the nanoflakes because they are converted back to colorless bulk α-MoO3.

Colorimetric aptasensor for progesterone detection based on surfactant-induced aggregation of gold nanoparticles.

This paper proposes an aptasensor for progesterone (P4) detection in human serum and urine based on the aggregating behavior of gold nanoparticles (AuNPs) controlled by the interactions among P4-binding aptamer, target P4 and cationic surfactant hexadecyltrimethylammonium bromide (CTAB). The aptamer can form an aptamer-P4 complex with P4, leaving CTAB free to aggregate AuNPs in this aptasensor. Thus, the sensing solution will turn from red (520 nm) to blue (650 nm) in the presence of P4 because P4 aptamers are used up firstly owing to the formation of an aptamer-P4 complex, leaving CTAB free to aggregate AuNPs. However, in the absence of P4, CTAB combines with aptamers so that AuNPs still remain dispersed. Therefore, this assay makes it possible to detect P4 not only by absorbance measurement but also through naked eyes. By monitoring the variation of absorbance and color, a CTAB-induced colorimetric assay for P4 detection was established with a detection limit of 0.89 nM. Besides, the absorbance ratio A650/A520 has a linear correlation with the P4 concentration of 0.89-500 nM. Due to the excellent recoveries in serum and urine, this biosensor has great potential with respect to the visual and instrumental detection of P4 in biological fluids.

Visual, rapid, and cost-effective BK virus detection system for renal transplanted patients using gold nanoparticle coupled loop-mediated isothermal amplification (nanoLAMP).

A substantial percentage of kidney transplant recipients show transplant failure due to BK virus-induced nephropathy. This can be clinically controlled by the rapid and timely detection of BK virus infection in immune-compromised patients. We report a rapid (two hours from sample collection, processing, and detection), cost-effective (< 2$), highly sensitive and BKV-specific nanoLAMP (loop-mediated isothermal amplification) diagnostic methodology using novel primers and gold nanoparticles complex-based visual detection. The standardized nanoLAMP showed an analytical sensitivity of 25 copies/µl and did not cross-react with closely related JC and SV40 viruses. This nanoLAMP showed diagnostic sensitivity and specificity as 91% and 96%, respectively, taking 50 BK virus-negative (confirmed by qPCR from the plasma of healthy donors) and 57 positive BKV patient samples (confirmed by clinical parameters and qPCR assay). This simple two-step, low-cost, and quick (1-2 h/test) detection would be advantageous over the currently used diagnostic methodology. It may change the paradigm for polyomavirus infection-based failure of renal transplant.

The Relationship between Anxiety, Visual Function, and Symptomatology in University Students.

Mental health concerns have emerged at the university level, with the psychological well-being of students being increasingly affected. This cross-sectional study investigated the proportion of university students having anxiety, and its effects on their visual function and symptomatology. We included 41 students (26.1 ± 4.8 years), and their visual function was assessed through several tests to produce a general visual performance index (VPI). The visual symptomatology was studied using the Conlon Visual Discomfort Survey and the Quality of Vision (QoV) questionnaire. The students were classified into two groups according to the Generalized Anxiety Disorder Screener (GAD-7) test ("no anxiety" and "anxiety" groups). The visual function evaluation indicated significantly worse VPI in the anxiety group (p = 0.047). These students also showed significantly higher scores in the Conlon survey (p = 0.004) and two subscales of the QoV questionnaire: symptom severity (p = 0.041) and symptom bothersomeness (p = 0.013). Moreover, the multiple linear regression model showed a significant association between visual discomfort according to the Conlon questionnaire and the level of anxiety (r = 0.405; R2 = 0.164; B = 0.405; p = 0.012). It is important to study the influence of psychological factors on vision, not only for refractive error, but also for binocular and accommodative disorders.

Single-Layered Two-Dimensional Metal-Organic Framework Nanosheets as an in Situ Visual Test Paper for Solvents.

Through a facile-operating ultrasonic force-assisted liquid exfoliation technology, the single-layered two-dimensional (2D) [Co(CNS)2(pyz)2] n (pyz = pyrazine) nanosheets, with a thickness of sub-1.0 nm, have been prepared from the bulk precursors. The atomically thickness and the presence of abundant sulfur atoms with high electronegativity arrayed on the double surfaces of the sheets are making this kind of 2D MOF (metal-organic framework) nanosheets highly sensitive to intermolecular interactions. As a result, it can be well dispersed in all kinds of solvents to give a stable colloidal suspension that can be maintained for at least one month, accompanied by significant solvatochromic behavior and various optical properties, which thus have shown the potential to be practically applicated as in situ visual test paper for solvent identification and solvent polarity measurements. More importantly, combined with a smartphone, this kind of 2D-MOF nanosheets can be developed into in situ visual test paper to identify isomers and determine the polarity of mixed solvents quantitatively and qualitatively, suggesting the promising application of a portable, economical, and in situ visual test strategy in real world.

Optical method for detecting oxygen via the chromogenic reaction catalyzed by polyphenol oxidase.

The present work describes a method for detecting the ingress of gas phase oxygen into packed food. It uses the enzyme polyphenol oxidase (PPO)from Mushroom and Mediterranean dwarf palm. The PPO is incorporated into an indubiose film along with a non-toxic polyphenol such as gallic acid or chlorogenic acid. If exposed to oxygen, the test spot undergoes an irreversible and visible color change from pale to deep brown due to the PPO catalyzed oxidation of the respective polyphenol by oxygen. The color change can be detected visually or by spectrophotometry at 470 nm. The effect of the amount of oxygen or substrate, type of enzyme substrate, enzyme source, temperature and duration of storage on the response were studied. Air oxygen can be detected within 30 min under optimized condition. The smallest amount of oxygen that can be detected with acceptable response time (120 min) is 5%. The test is highly selective for oxygen and the detector is stable over time. The detector may be used in any application as long as the presence or absence of oxygen in a sealed space is determined prior to the application using the detector.

Assessment of occupational exposure to gaseous peracetic acid.

OBJECTIVES: In order to assess short-term exposure to peracetic acid (PAA) in disinfection processes, the Authors compared 4 industrial hygiene monitoring methods to evaluate their proficiency in measuring airborne PAA concentrations. MATERIAL AND METHODS: An active sampling by basic silica gel impregnated with methyl p-tolyl sulfoxide (MTSO), a passive solid phase micro-extraction technique using methyl p-tolyl sulfide (MTS) as on-fiber derivatization reagent, an electrochemical direct-reading PAA monitor, and a novel visual test strip PAA detector doped with 2,2'-azino-bis (3-ethylbenzothiazoline)-6-sulfonate were evaluated and tested over the range of 0.06-16 mg/m3, using dynamically generated PAA air concentrations. RESULTS: The linear regression analysis of linearity and accuracy showed that the 4 methods were suitable for PAA monitoring. Peracetic acid monitoring in several use applications showed that the PAA concentration (1.8 mg/m3) was immediately dangerous to life or health as proposed by the National Institute of Occupational Safety and Health, and was frequently exceeded in wastewater treatment (up to 7.33 mg/m3), and sometimes during food and beverage processes and hospital high-level disinfection operations (up to 6.8 mg/m3). CONCLUSIONS: The methods were suitable for the quick assessment of acute exposure in PAA environmental monitoring and can assist in improving safety and air quality in the workplace where this disinfectant is used. These monitoring methods allowed the evaluation of changes to work out practices to reduce PAA vapor concentrations during the operations when workers are potentially overexposed to this strong antioxidant agent. Int J Occup Med Environ Health 2018;31(4):527-535.

Behavioral Differences in the Upper and Lower Visual Hemifields in Shape and Motion Perception.

Perceptual accuracy is known to be influenced by stimuli location within the visual field. In particular, it seems to be enhanced in the lower visual hemifield (VH) for motion and space processing, and in the upper VH for object and face processing. The origins of such asymmetries are attributed to attentional biases across the visual field, and in the functional organization of the visual system. In this article, we tested content-dependent perceptual asymmetries in different regions of the visual field. Twenty-five healthy volunteers participated in this study. They performed three visual tests involving perception of shapes, orientation and motion, in the four quadrants of the visual field. The results of the visual tests showed that perceptual accuracy was better in the lower than in the upper visual field for motion perception, and better in the upper than in the lower visual field for shape perception. Orientation perception did not show any vertical bias. No difference was found when comparing right and left VHs. The functional organization of the visual system seems to indicate that the dorsal and the ventral visual streams, responsible for motion and shape perception, respectively, show a bias for the lower and upper VHs, respectively. Such a bias depends on the content of the visual information.

Sensory quality of lamb following long-term frozen storage.

The study analysed the effect of frozen storage duration (FSD) on lamb sensory quality. Trained panel evaluated Longissimus lumborum aged for 1d in unfrozen carcass plus 3d in modified atmosphere packaging on thawed (1, 9, 15 or 21 month FSD) or refrigerated (0 month FSD) meat. Consumer acceptability test was performed on leg chops (Semimembranosus) kept in the same conditions but those chops for the visual test were retail displayed up to 10d from packaging. FSD differed on texture variables and fresh meat showed intermediate values among thawed meats for trained evaluators. Consumers gave the lowest acceptability to 21 months FSD and preferred 1 month FSD, being all meats 'acceptable'. A third of the population scored fresh meat with the lowest acceptance after consumption, although its visual score remained 'acceptable' 3d longer than most of thawed meats. As thawed and fresh meats were equally preferred at short display, consumer concerns about thawed meat might be reconsidered.

Cathodal HD-tDCS on the right V5 improves motion perception in humans.

Brain lesions in the visual associative cortex are known to impair visual perception, i.e., the capacity to correctly perceive different aspects of the visual world, such as motion, color, or shapes. Visual perception can be influenced by non-invasive brain stimulation such as transcranial direct current stimulation (tDCS). In a recently developed technique called high definition (HD) tDCS, small HD-electrodes are used instead of the sponge electrodes in the conventional approach. This is believed to achieve high focality and precision over the target area. In this paper we tested the effects of cathodal and anodal HD-tDCS over the right V5 on motion and shape perception in a single blind, within-subject, sham controlled, cross-over trial. The purpose of the study was to prove the high focality of the stimulation only over the target area. Twenty one healthy volunteers received 20 min of 2 mA cathodal, anodal and sham stimulation over the right V5 and their performance on a visual test was recorded. The results showed significant improvement in motion perception in the left hemifield after cathodal HD-tDCS, but not in shape perception. Sham and anodal HD-tDCS did not affect performance. The specific effect of influencing performance of visual tasks by modulating the excitability of the neurons in the visual cortex might be explained by the complexity of perceptual information needed for the tasks. This provokes a "noisy" activation state of the encoding neuronal patterns. We speculate that in this case cathodal HD-tDCS may focus the correct perception by decreasing global excitation and thus diminishing the "noise" below threshold.

Colorimetric Au nanoparticle probe for speciation test of arsenite and arsenate inspired by selective interaction between phosphonium ionic liquid and arsenite.

The exposure of millions of people to unsafe levels of arsenite (AsIII) and arsenate (AsV) in drinking waters calls for the development of low-cost methods for on-site monitoring these two arsenic species in waters. Herein, for the first time, tetradecyl (trihexyl) phosphonium chloride ionic liquid was found to selectively bind with AsIII via extended X-ray absorption fine structure (EXAFS) analysis. Based on the finding, an AsIII-specific probe was developed by modifying gold nanoparticles with the ionic liquid. Futhermore, Hofmeister effect was primarily observed to significantly affect the sensitivity of gold nanoparticle probe. With the colorimetric probe, we developed a protocol for naked eye speciation test of AsIII and AsV at levels below the World Health Organization (WHO) guideline of 10 µg L(-1). This method featured with high tolerance to common coexisting ions such as 10 mM PO4(3-), and was validated by assaying certified reference and environmental water samples.

Antioxidant diet supplementation and lamb quality throughout preservation time.

Diet supplementation (DS) (100, 200, 300ppm vitamin E -VE; 150ppm product rich in flavonoids-PRF; 100+100ppm VE-PRF; no supplementation) effect was evaluated on lamb quality throughout 10days after sampling (preservation time: PT). pH, colour, myoglobin forms and lipid oxidation were analyzed on Longissimus muscle. Trained panellists evaluated colour intensity of chops packaged in modified atmosphere under display up to 12days. PT had a larger effect on quality than DS. DS showed a clear antioxidant effect on lipids, especially at long PT and at high doses of VE. Visual test showed statistical differences among DS from day 4 of display where 200 and 300ppm VE improved visual colour score. In general, supplementation with antioxidants showed better meat quality and diets higher than 100ppm VE showed higher antioxidant capacity than the rest. The PRF diet was similar for a short PT but lower at a long PT. More research on flavonoids is necessary.