Measurement of the index of refraction (the ratio of the velocity of light or other radiation in the first of two media to its velocity in the second as it passes from one into the other).

Tonic accommodation, age, and refractive error in children. (1/409)

PURPOSE: An association between tonic accommodation, the resting accommodative position of the eye in the absence of a visually compelling stimulus, and refractive error has been reported in adults and children. In general, myopes have the lowest (or least myopic) levels of tonic accommodation. The purpose in assessing tonic accommodation was to evaluate it as a predictor of onset of myopia. METHODS: Tonic accommodation was measured in children enrolled in the Orinda Longitudinal Study of Myopia using an infrared autorefractor (model R-1; Canon, Lake Success, NY) while children viewed an empty lit field or a dark field with a fixation spot projected in Maxwellian view. Children aged 6 to 15 years were measured from 1991 through 1994 (n = 714, 766, 771, and 790 during the 4 years, successively). Autorefraction provided refractive error and tonic accommodation data, and videophakometry measured crystalline lens curvatures. RESULTS: Comparison of the two methods for measuring tonic accommodation shows a significant effect of age across all years of testing, with the lit empty-field test condition yielding higher levels of tonic accommodation compared with the dark-field test condition in children aged 6 through 11 years. For data collected in 1994, mean (+/-SD) tonic accommodation values for the lit empty-field condition were significantly lower in myopes, intermediate in emmetropes, and highest in hyperopes (1.02 +/- 1.18 D, 1.92 +/- 1.59 D, and 2.25 +/- 1.78 D, respectively; Kruskal-Wallis test, P < 0.001; between-group testing shows each group is different from the other two). Age, refractive error, and Gullstrand lens power were significant terms in a multiple regression model of tonic accommodation (R2 = 0.18 for 1994 data). Lower levels of tonic accommodation for children entering the study in the first or third grades were not associated with an increased risk of the onset of myopia, whether measured in the lit empty-field test condition (relative risk = 0.90; 95% confidence interval = 0.75, 1.08), or the dark-field test condition (relative risk = 0.83; 95% confidence interval = 0.60, 1.14). CONCLUSIONS: This is the first study to document an association between age and tonic accommodation. The known association between tonic accommodation and refractive error was confirmed and it was shown that an ocular component, Gullstrand lens power, also contributed to the tonic accommodation level. There does not seem to be an increased risk of onset of juvenile myopia associated with tonic accommodation.  (+info)

A new approach to the study of ocular chromatic aberrations. (2/409)

We measured the ocular wavefront aberration at six different visible wavelengths (between 450 and 650 nm) in three subjects, using a spatially resolved refractometer. In this technique, the angular deviation of light rays entering the pupil at different locations is measured with respect to a target viewed through a centered pupil. Fits of the data at each wavelength to Zernike polynomials were used to estimate the change of defocus with wavelength (longitudinal chromatic aberration, LCA) and the wavelength-dependence of the ocular aberrations. Measured LCA was in good agreement with the literature. In most cases the wavefront aberration increased slightly with wavelength. The angular deviations from the reference stimulus measured using a magenta filter allowed us to estimate the achromatic axis and both optical and perceived transverse chromatic aberration (TCA), (including the effect of aberrations and Stiles-Crawford effect). The amount of TCA varied markedly across subjects, and between eyes of the same subject. Finally, we used the results from these experiments to compute the image quality of the eye in polychromatic light.  (+info)

Optical characterization of liposomes by right angle light scattering and turbidity measurement. (3/409)

Liposomes have frequently been used as models of biomembranes or vehicles for drug delivery. However, the systematic characterization of lipid vesicles by right angle light scattering and turbidity has not been carried out despite the usefulness of such studies for size estimation. In this study, liposomes of various sizes were prepared by sonication and extrusion. The mean cumulant radii of the vesicles were determined by dynamic light scattering. The lamellarities were estimated based on fluorescence quenching of N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)dipalmitoyl-L-alpha-phosph ati dylethanolamine by sodium dithionite. Right angle light scattering intensity and optical density at 436 nm per unit lipid concentration were measured as a function of vesicle radius. With a vesicle radius < or =100 nm, the optical parameters could be well explained by the Rayleigh-Gans-Debye theory in which the liposomes were modeled as homogeneous spheres with mean refractive indices determined by the volume fractions of lipids in vesicles.  (+info)

High-performance liquid chromatographic determination of glycogen in sea urchin gonads with refractive index detection. (4/409)

A high-performance liquid chromatographic method using refractive index detection for the determination of glycogen in sea urchin (Paracentrotus lividus) gonads is developed. After alkaline digestion with sodium carbonate, samples are adjusted to pH 4.6 with citric acid and incubated with amyloglucosidase to hydrolyze the glycogen. The resulting glucose is determined using a Spherisorb NH2 column as the stationary phase and an acetonitrile-water mixture (80:20, v/v) as the mobile phase. The relative standard deviation (%) was 3.57, the limit of detection was 40.1 microg/mL, and the recovery percentage was 97.2%.  (+info)

Lens growth and protein density in the rat lens after in vivo exposure to ultraviolet radiation. (5/409)

PURPOSE: To investigate lens growth after different doses of ultraviolet radiation (UVR) and to investigate the long-term effect of a near-threshold UVR dose on the refractive index distribution in the lens. METHODS: Sprague-Dawley rats received UVR (lambda(MAX) = 300 nm) unilaterally during a 15-minute period. The exposure dose ranged from 0.1 to 20 kJ/m(2), and the rats were kept for up to 32 weeks after exposure. Intact lenses were photographed and lens wet and dry masses were measured. The protein density was estimated by quantitative microradiography. Freeze-dried lens sections were used for contact x-ray photographs. From the transmission of the microradiographs, protein density and refractive index profiles were calculated along the lens radius with a resolution of 2.5 microm. RESULTS: Lens dry mass in exposed eyes was lower than in nonexposed eyes at one week after exposure. Lens water content was decreased after low UVR doses but increased after high doses. The difference between exposed and nonexposed lenses in dry mass and water content increased with time after exposure. No significant difference was found for the mean protein density in exposed and nonexposed lenses. The protein density increased linearly in the lens cortex, from a minimum in the superficial cortex of 0.26 g/cm(3) to a maximum in the deep cortex of 0.81 g/cm(3). This corresponded to a refractive index of 1.38 and 1.48, respectively. CONCLUSIONS: Lenses exposed to UVR grew more slowly than their nonexposed contralaterals. This growth inhibition was dose dependent. Near-threshold doses led to decreased water content in the lens whereas high doses led to swelling. Six months after near-threshold UVR exposure, no global change of the refractive index was found. However, local variations of the refractive index caused a subtle cortical light scattering.  (+info)

Computational adaptive optics for live three-dimensional biological imaging. (6/409)

Light microscopy of thick biological samples, such as tissues, is often limited by aberrations caused by refractive index variations within the sample itself. This problem is particularly severe for live imaging, a field of great current excitement due to the development of inherently fluorescent proteins. We describe a method of removing such aberrations computationally by mapping the refractive index of the sample using differential interference contrast microscopy, modeling the aberrations by ray tracing through this index map, and using space-variant deconvolution to remove aberrations. This approach will open possibilities to study weakly labeled molecules in difficult-to-image live specimens.  (+info)

Gradient refractive index of the crystalline lens of the Black Oreo Dory (Allocyttus Niger): comparison of magnetic resonance imaging (MRI) and laser ray-trace methods. (7/409)

The gradient refractive index of the crystalline lens in the Black Oreo Dory (Allocyttus Niger) was determined using two methods; an optimisation program based on finite ray-tracing and the path of laser beams through the lens, and magnetic resonance imaging (MRI) and the linear relationship between refractive index and nuclear transverse relaxation rates. The methods showed good agreement in the cortical zone of the lens, but the lack of free water in the core of the lens made MRI measurement impossible in this region. The laser-optimisation method gave mean values of 1.368 and 1.543 for the surface and core refractive indices respectively, with a radial distribution for the gradient refractive index given by n(r)=1.543-0.121r2-0.033r4-0.021r6.  (+info)

Index matching to improve optical coherence tomography imaging through blood. (8/409)

BACKGROUND: Most myocardial infarctions are caused by the rupture of small rather than large plaques in the arteries of the heart that are beyond the detection limit of current technologies. METHODS AND RESULTS: Recently, optical coherence tomography (OCT) has demonstrated considerable potential as a method for high-resolution assessment of vulnerable plaque. However, intravascular OCT imaging is complicated by the need to remove blood from the imaging field because blood results in substantial signal attenuation. This work examines index matching as a method for increasing penetration. Index matching is based on the hypothesis that the predominant source of scattering in blood is the difference in refractive index between the cytoplasm of erythrocytes and serum. By increasing the refractive index of serum to a value near that of the cytoplasm, or index matching, scattering can be substantially reduced. The concept was tested with a system that pumped blood in vitro through transparent tubing. The test compounds, dextran and intravenous contrast agent, both led to significant improvements in penetration (69+/-12% and 45+/-4%). No significant effect was seen with the saline control. For dextran, the effect could not be attributed to reductions of red cell number or volume because changes in these parameters were not different from the control. In the case of intravenous contrast, a small but significant relative reduction in red cell volume was seen. CONCLUSIONS: This study demonstrates the feasibility of index matching for improving OCT imaging through blood. Future studies are required to identify compounds for effective index matching in vivo.  (+info)

Refractometry is a medical laboratory technique used to measure the refractive index of a substance, typically a liquid. The refractive index is the ratio of the speed of light in a vacuum to its speed in the substance being measured. In a clinical setting, refractometry is often used to determine the concentration of total solids in a fluid, such as urine or serum, by measuring the angle at which light passes through the sample. This information can be useful in the diagnosis and monitoring of various medical conditions, including dehydration, kidney disease, and diabetes. Refractometry is also used in the field of optometry to measure the refractive error of the eye, or the amount and type of correction needed to provide clear vision.

... is also used in the gelatin industry. To convert the RI of a gelatin sol (reported in Brix) to a gelatin ... Refractometry is the analytical method of measuring substances' refractive index (one of their fundamental physical properties ... ISBN 0-7503-0966-0. Refractometry - Gemstone Buzz methods for measuring refractive index. (Measurement). ...
"Refractometers and refractometry". Refractometer.pl. 2011. Archived from the original on 2011-10-20. Retrieved 2011-09-03. " ... material Index ellipsoid Laser Schlieren Deflectometry Optical properties of water and ice Prism-coupling refractometry Phase- ...
"Ultrasensitive Refractometry via Supercritical Angle Fluorescence". ACS Nano.{{cite journal}}: CS1 maint: multiple names: ...
cit.; Specification and Standard SPS-3 Refractometry and Tables - Official; Tables A-F Buhl, Josh. "Physical Equations Relating ... the sugar content of a solution obtained by use of refractometry with the ICUMSA table is often reported as "Refractometric Dry ...
In addition to thermal migration, he also conducted research on refractometry. In 1898, he became the rector of the University ...
Okita, K.; Teramoto, A.; Kawahara, K.; Fujita, H. (1968). "Light scattering and refractometry of a monodisperse polymer in ...
Surface plasmon resonance-based instruments use refractometry to measure and analyze biomolecular interactions. Magic lantern ...
A refractometer is a laboratory or field device for the measurement of an index of refraction (refractometry). The index of ... Rayleigh Refractometer: Operational Principles Archived 2018-07-05 at the Wayback Machine Refractometers and refractometry ...
He is known for more than 30 technical patents in the area of refractometry, measurement, and control. Vossberg also founded ... was granted more than 30 technical patents during his lifetime in the areas of refractometry, measurement, and control. A ...
More recently immersion refractometry has been shown to be a viable method for continuous monitoring of the state of charge. ...
Among these are methods for determination of dry solids content by polarimetry, densimetry and refractometry, color (extinction ... Specification and Standard SPS-3 (2000) Refractometry and Tables Reichert Analytical Instruments, AR200 Refractometer User's ...
... but other chemical methods such as dye-binding and refractometry are now available. The measurement is usually performed on ...
... measures intraocular pressure and performs refractometry. They also provide patients with explanations of procedures and answer ...
... refractometry MeSH H01.671.628 - oscillometry MeSH H01.671.660 - phase transition MeSH H01.671.670 - porosity MeSH H01.671.691 ...
In medicine, particularly optometry, ophthalmology and orthoptics, refraction (also known as refractometry) is a clinical test ...
UV absorption and differential refractometry, if the copolymer is composed of two base polymers that provide different ...
... of arterial pulse-wave velocity Measurement of visual acuity Measurement of intra-ocular pressure Lens refractometry Fundus ...
Refractometry is also used in the gelatin industry. To convert the RI of a gelatin sol (reported in Brix) to a gelatin ... Refractometry is the analytical method of measuring substances refractive index (one of their fundamental physical properties ... ISBN 0-7503-0966-0. Refractometry - Gemstone Buzz methods for measuring refractive index. (Measurement). ...
Basics of refractometry. Measurement of the refractive index can be used to characterize liquid and solid samples, for example ...
Measuring Refractive Index or Refractometry is the method of measuring substances refractive index - assess their composition ... Refractometry Definition - Measuring Refractive Index. Refractive Index Measurement or Refractometry is the method of measuring ... Since the late nineteenth century refractometry was one of the main techniques used in chemical analysis. Refractometry was ... Refractometry is a technique that measures how light is refracted when it passes through a given substance. Snells Law which ...
How does a refractometer work? How do we use a refractometer? What is it used for, and what cant it be used for ...
Dive into the research topics of Refractometry of controlled substances [4]. Together they form a unique fingerprint. ...
Refractometry. Fast determination of the refractive index for optical surface characterization. One of the most important ...
Label-free biosensing by ultrasensitive supercritical angle refractometry. Lucien E. Weiss, Boris Ferdman, Onit Alalouf, Yoav ... Label-free biosensing by ultrasensitive supercritical angle refractometry. / Weiss, Lucien E.; Ferdman, Boris; Alalouf, Onit et ... title = "Label-free biosensing by ultrasensitive supercritical angle refractometry",. abstract = "By imaging the back focal ... Dive into the research topics of Label-free biosensing by ultrasensitive supercritical angle refractometry. Together they ...
EasyDirect Density and Refractometry. Results can be viewed directly on the portable refractometer. For even more flexibility, ... export your results from the Refracto 30PX/30GS to EasyDirect™ Density and Refractometry PC Software. Review and filter your ...
Soil quality - Screening method for water content - Determination by refractometry
Examining the Impact of Particulate Matter in Refractometry for Coffee Assessment. by Jeremy , posted in: Brewing, ...
An Introduction to Refractometry Youve lost the key to your locker in the swimming pool. You spot it lying on the bottom of ...
Refractometry *Nucleophilic Substitution Reactions, Competing Nucleophiles. *Preparation of Cyclohexene. *Polarimetry. Learning ...
Contents Dedication Acknowledgments About the Author Preface JANUARY Retinal Tears and Holes...2 • Fuchs Heterochromic Iridocyclitis...3 • Arteritic Anterior Ischemic Optic Neuropathy...4 • Louis Braille...5 • Chromatic Aberration...6 • Diabetic Retinopathy Study...7 • Polarized Lenses...8 • Corneal Abrasion...9 • Irregular Astigmatism...10 • Clotting Studies...11 • Claude Monets Cataracts...12 • Anterior Basement Membrane Dystrophy...13 • TORCHES...14 • Branch Retinal Artery Occlusion...15 • Presbyopia-Correcting Intraocular Lens Implants...16 • Adies Tonic Pupil...17 • Excimer Laser Tracking Systems (Trackers)...18 • Allergic Conjunctivitis...19 • J. Donald Gass...20 • Toxic Anterior Segment Syndrome...21 • Chemical Injury...22 • Acquired Esotropia...23 • Visual Perception...24 • Corticosteroid Response Glaucoma...25 • Craniopharyngioma...26 • Transient Monocular Visual Loss...27 • Herpetic Eye Disease Study...28 • Aniridia...29 • ...
The latter method can achieve refractometry without the need for spectroscopy tools, provided certain criteria explained in the ... In the scope of miniaturized optical sensors for liquid refractometry, this work details the design, numerical simulation, and ... In the scope of miniaturized optical sensors for liquid refractometry, this work details the design, numerical simulation, and ... The latter method can achieve refractometry without the need for spectroscopy tools, provided certain criteria explained in the ...
Theoretical Investigation of Global Rainbow Refractometry in Spray Combustion of Polydisperse Microdroplets M.F.B. Stodt, T. ... Change of evaporation rate of single monocomponent droplet with temperature using time-resolved phase rainbow refractometry Y. ...
Retinoscopy and Auto-refractometry. These are objective tests for test your capability to see images clearly, which dont ...
Refractometry has never been so easy! With simple operating routines and an intuitive touch screen user interface, you can ... Brochure: Density and Refractometry Excellence. Developed for a wide range of applications, our intuitive instruments measure ... Datasheet: Refractometry Excellence. Developed for a wide range of applications, our intuitive Excellence Refractometers will ...
SPIE 2208, Refractometry, (23 June 1995); doi: 10.1117/12.213178. Show Author Affiliations. Lothar U. Kempen, Paul Scherrer ...
Refractometry in-house method URI1. Blood groupingFor companion animals Whole blood Canine blood groups - DEA; Feline blood ...
Refractometry provides an alternative method to determine the concentration. Refractometry is advantageous in that the ...
Differential refractometry US2904687A (en) 1959-09-15. Differential radiation absorption measurement system ...
Thermal control in minimum-deviation refractometry and temperature coefficients for a medium flint glass, p. 389 Tilton, Leroy ...
Refractometry. *8. Electric conductivity. Refractometry. *9. Spectroscopy and spectrophotometry. *10. Spectroscopy and ...
The device was strongly correlated to optical refractometry with a mean absolute error of 0.0029 (±0.0021). Our results show ... The device was strongly correlated to optical refractometry with a mean absolute error of 0.0029 (± 0.0021). Our results show ... manual optical refractometry. Large dots represent averages at each USG range (,1.015, 1.015−1.025, ,1.025). Error bars ... Analytical performance studies (Figure 2A) demonstrated strong correlation to manual optical refractometry (r = 0.90; n = 247 ...
Refractometry - its applications and methods.. 54537 Food Analysis/ Lab. Studying the general methods of the food analysis ...
Refractometry & Polarimetry. News - with Gwyneth Astles. - Exclusive Gathering of Pharmaceutical Lab Equipment in China. - ...
Refractometry & Keratometry Measurement. PRK-8000 provides an extensive dioptric measurement range [-30D to +25D] compared to ...
Fabry-Pérot based refractometry: development of a transportable refractometer for assessment of gas pressure ...
On such production facilities the non-invasive FLUXUS flow meter is used for the flow measurement of TEG at very high pressures of 3000 to 4500 psi. The clamp-on flow measurement is independent of the process pressure. The ultrasonic transducers are simply clamped onto the pipe and do not come into contact with the toxic medium. No cutting or tapping of the pipe is needed for installation; all potential leakage sources are thus avoided.. Additionally, the PIOX R Process Refractometer measures the concentration levels of the glycol circulating in the towers and provides the storage operators with the relevant infomations for a proper process conrol.. ...
Performs lensometry, automated refractometry, slit lamp examination including applanation tonometry, anterior chamber angle ...
  • Refractive Index Measurement or Refractometry is the method of measuring substances refractive index and assess their composition or purity. (rudolphresearch.com)
  • The Brix degrees measurement was made by refractometry using an Abbé refractometer and the pH was evaluated using potentiometry. (bvsalud.org)
  • Course content ranges from the basics of history taking, medical ethics, eye and visual system anatomy, physiology, and pathology and patient relations to specialty areas including lensometry, refractometry, optical coherence tomography, ophthalmic imaging and surgical assisting. (usc.edu)
  • Refractometry is the analytical method of measuring substances' refractive index (one of their fundamental physical properties) in order to, for example, assess their composition or purity. (wikipedia.org)
  • Refractometry - Gemstone Buzz methods for measuring refractive index. (wikipedia.org)
  • The latter method can achieve refractometry without the need for spectroscopy tools, provided certain criteria explained in the details are met. (hal.science)
  • Refractometry was used to determine concentrations of solutions and as an aid in the identification of unknown substances. (rudolphresearch.com)
  • The most significant finding was a low plasma and serum protein both on refractometry and using the biuret method of analysis. (vin.com)
  • In the scope of miniaturized optical sensors for liquid refractometry, this work details the design, numerical simulation, and experimental characterization of a Fabry-Pérot resonator consisting of two deeply-etched silicon cylindrical mirrors with a micro-tube in between holding the liquid analyte under study. (hal.science)
  • The device was strongly correlated to optical refractometry with a mean absolute error of 0.0029 (±0.0021). (frontiersin.org)
  • Refractometry is a technique that measures how light is refracted when it passes through a given substance. (rudolphresearch.com)
  • It is often used in refractometry to describe the relationship angles of incidence and light. (rudolphresearch.com)
  • We also offer unique instruments for electrophoretic light scattering (ELS), differential refractometry and differential viscosity. (wyatt.com)
  • Refractometry is also used in the gelatin industry. (wikipedia.org)
  • In business for more than 70 years, we are respected as an industry leader in the field of refractometry. (misco.com)
  • Refractometry is the analytical method of measuring substances' refractive index (one of their fundamental physical properties) in order to, for example, assess their composition or purity. (wikipedia.org)
  • Refractometry - Gemstone Buzz methods for measuring refractive index. (wikipedia.org)
  • Refractometry is an optical analysis technique used to establish the refractive index of transparent and translucent substances. (measurlabs.com)
  • The principle of refractometry is based on a transparent or translucent material's ability to refract and shift light, also known as its refractive index. (measurlabs.com)
  • Refractometry is used to measure the refractive index of a substance in order to determine its composition or purity. (electronmachine.com)
  • Finally, www.refractometer.pl is a site where we try to post information about refractometers and refractometry as used in chemistry. (chembuddy.com)
  • We also offer unique instruments for electrophoretic light scattering (ELS), differential refractometry and differential viscosity. (wyatt.com)
  • His most salient innovations are considered to have been: (a) the use of refractometry to estimate serum total protein concentration, (b) the use of conductivity measurements to estimate serum total base (in the era before flame photometry made measurements of Na and K practical), and (c) biological monitoring of urine nickel concentrations to detect industrial exposures to nickel. (medscape.com)
  • A paper has demonstrated a novel refractometry-based process analytical technology (PAT) system has potential for enabling adaptive process control in CGT manufacturing. (europeanpharmaceuticalreview.com)
  • Experimental validation of the intensity refractometry principle for density measurements at the edge of a tokamak. (mpg.de)
  • Urine specific gravity (USG) was measured by refractometry on the competition day's first morning urine sample. (humankinetics.com)
  • Refractometry" is a descriptor in the National Library of Medicine's controlled vocabulary thesaurus, MeSH (Medical Subject Headings) . (harvard.edu)
  • In the scope of miniaturized optical sensors for liquid refractometry, this work details the design, numerical simulation, and experimental characterization of a Fabry-Pérot resonator consisting of two deeply-etched silicon cylindrical mirrors with a micro-tube in between holding the liquid analyte under study. (hal.science)
  • Children underwent noncycloplegic refractometry every six months and axial length (AL) measurements every year. (reviewofoptometry.com)
  • This graph shows the total number of publications written about "Refractometry" by people in Harvard Catalyst Profiles by year, and whether "Refractometry" was a major or minor topic of these publication. (harvard.edu)
  • Refractometry has been used extensively in product testing and drug development. (nih.gov)
  • Refractometry finds significant use in the food and drink industries, where it is used to perform quality control testing on sugars, oils, beverages, and many other products. (measurlabs.com)