[Method of reduction of the "instrumental" accommodation in refractometry].
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Accommodation, Ocular↗
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[Automated refractometry after optical reconstructive operations].
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Astigmatism↗
[Evaluation of cycloplegic drugs based on results of refractometry].
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Accommodation, Ocular↗
[Objective determination of refraction].
Objective determination of refraction is basically necessary for the subjective adjustment of refraction aimed at prescribing glasses. At least as important is the use of objective determination of refraction as a basis of ophthalmological diagnosis because the best-corrected visual acuity forms basic diagnostic information. Three methods of objective determination of refraction are available. Photorefraction has only been used for screening preschool children, as it has no value for the above-mentioned purpose. Refractometry is widely being used for objective determination of refraction, and during the last few years automated refractometry has also become more and more common. This trend is supported by the possibility of delegating automated refractometry to assistant medical personnel. Retinoscopy and automated refractometry yield comparable results. Retinoscopy has some advantages: great flexibility and the fact that retinoscopy forms an image of optical aberrations of the eye, giving the ophthalmologist an idea of the optical quality of the patient's eye. Due to its flexibility retinoscopy can be used for refractioning babies and infants without any problem. The disadvantage of retinoscopy is the impossibility of delegating it to assistant medical personnel and the fact that this method must be learned by the ophthalmologist. In contrast to retinoscopy, automated refractometry can easily be learned and can be delegated to assistant medical personnel. Its drawback is that it is inflexible, making it inconvenient for refractioning babies and infants. If automated refractometry and retinoscopy are used with cycloplegia, precautions are essential to avoid errors caused by optical aberrations of the eye. The measurement must be done in the center of the pupil.(ABSTRACT TRUNCATED AT 250 WORDS)
Eyeglasses↗
Projection-simulated ametropia. A model for teaching subjective refraction.
Teaching subjective refraction techniques ("refractometry") is enhanced by having the student experience the effect of each lens change "through the eyes of the patient." A projector, positioned behind the phoropter, projects a visual acuity chart through the phoropter onto the far wall. "Unknown" refractive errors are simulated by attaching trial lenses to the lens barrel of the projector, and the student progressively clears the projected image as he learns the standard steps of subjective refractometry. The focus sensitivity of each lens change can be varied, if desired, by stopping down the projection system. This simulation, which uses equipment readily available in most ophthalmology offices, has proven useful for both demonstration and practice.
Education, Medical↗
Concentration and composition of plasma proteins in wild mammals.
Total protein concentrations from a variety of wild mammalian species were measured by the Lowry and Biuret techniques and compared with results obtained or derived by refractometry. Values obtained with the Lowry method were the highest and certain derived refractometry results, the lowest. It is suggested that the Biuret method provides the most acceptable values but that care should be exercised in using the correct standard. The percentage composition of plasma from 22 species of wild mammals is also presented and the observations discussed with relation to methodology and A/G ratio.
Animal Population Groups↗
Thermodynamic characterization of hog kidney D-amino acid oxidase apoenzyme in concentrated guanidine hydrochloride solution. Preferential interaction with the solvent components and the molecular weight of the monomeric unit.
This paper describes the physical characterization of the monomeric unit of hog kidney D-amino acid oxidase apoenzyme in 6 M guanidine hydrochloride (GuHCl) solution by means of differential refractometry, densimetry, light scattering, equilibrium sedimentation, and high-speed gel filtration chromatography. In 6 M GuHCl solution, the oxidase interacts preferentially with GuHCl: the values of the preferential interaction parameter are 0.11 +/- 0.03 (S.D.) g/g of protein by densimetry and 0.14 +/- 0.04 g/g of protein by refractometry. The volume change, delta V, of the oxidase on transfer from the native to the denatured state is -350 ml/mol. The molecular weight of the monomeric apoenzyme is 39,600 +/- 1,700 by light scattering and 38,000 +/- 1,200 by high-speed equilibrium sedimentation. The values of the molecular weight estimated by the empirical methods, i.e., sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis and high-speed gel filtration chromatography in 6 M GuHCl, agree well with those obtained by the thermodynamic methods mentioned above. These results confirm definitely that the complex of the apoenzyme with SDS normally behaves in the same manner as those of standard proteins in SDS-gel electrophoresis. This is also supported in this study by the analysis of the electrophoretic data at several gel concentrations by Ferguson plots. The molecular weight of quasi-D-amino acid oxidase apoenzyme was also examined by the empirical methods.
Animals↗
Subunit constitution of carbonic anhydrase from Chlamydomonas reinhardtii.
Carbonic anhydrase purified from the cell surface of Chlamydomonas reinhardtii was inactivated by treatment with dithiothreitol. This treatment caused dissociation of the holoenzyme into 35-kDa (A) and 4-kDa (B) subunits as revealed by SDS/PAGE. The 35-kDa subunit was further separated into two components A1 (35 kDa) and A2 (36.5 kDa) by SDS/PAGE using a gradient gel. These two components have the same amino acid sequence up to at least the 10th amino acid from the N-terminus. The molecular masses were estimated at 76 kDa and 35 kDa for the holoenzyme and the large subunit, respectively, and the molar ratio of the former to the latter at 1:2, by using the techniques of low-angle laser light-scattering photometry and precision differential refractometry combined with gel-filtration HPLC. The molar ratio of the 35-kDa/4-kDa subunits was estimated at 1:1 the gel-filtration HPLC monitored with precision differential refractometry. Atomic-absorption spectrophotometry revealed that the holoenzyme contains two atoms of zinc. These results suggest that the holoenzyme is a heterotetramer composed of two large subunits (A1 and A2) and two small subunits (B).
Amino Acid Sequence↗
[Analysis of solutions for parenteral use under field conditions].
Methods for determination of relative density, osmolarity, then refractometry, polarymetry and conductometry as simple methods suitable for work under field conditions have been applied for the quality control of the following solutions for infusion and injections: glucose, mannitol, sodium chloride, sodium hydrogencarbonate, magnesium sulphate and potassium chloride. The results obtained in the analysis of preparations have shown the advantage of refractometry.
Infusions, Parenteral↗
Active and monomeric human red cell glucose transporter after high performance molecular-sieve chromatography in the presence of octyl glucoside and phosphatidylserine or phosphatidylcholine.
The human red cell glucose transporter (Glut 1) was purified by ion-exchange chromatography in the presence of octyl glucoside. The state of association of the protein was studied, and the transport activity was determined after exchange of copurified membrane lipids for phosphatidylserine (PS) or phosphatidylcholine (PC). The purpose was to analyze the Glut 1 preparation for homogeneity and activity prior to attempts at crystallization. Analyses by high performance molecular-sieve chromatography showed that the Glut 1 was monomeric immediately after the ion-exchange purification: the Mr of the Glut 1 polypeptide was estimated to be 49,000 +/- 6000 by TSKgel G3000SW chromatography monitored by low-angle laser light-scattering photometry, differential refractometry and UV photometry. This required determination of the absorption coefficient of the Glut 1, which was measured to be 1.13 +/- 0.03 ml mg-1 cm-1 at 280 nm, referring to the polypeptide concentration. The Mr value is consistent with the cDNA-deduced Mr 54,117 of the very similar HepG2 glucose transporter polypeptide. At 2 degrees C, pH 7 and an ionic strength of 0.06 M, the Glut 1 associated gradually during three days to form oligomers. These formed much more rapidly at room temperature or at high ionic strength. Freshly prepared Glut 1 retained high activity after separation from membrane lipids on a TSKgel G3000SW column in the presence of 40 mM octyl glucoside and 1 mM PS or PC. In contrast, most of the activity was lost when the membrane lipids were separated from the protein in the absence of eluent lipids. The presence of a phospholipid was thus essential for retention of high activity of the Glut 1 in octyl glucoside and PC was nearly as effective as PS.
Chromatography, Gel↗
Determination of cholesterol and cortisone absorption in polyurethane. I. Methodology using size-exclusion chromatography and dual detection.
A size-exclusion chromatographic method is described for measuring the absorption of the steroid-based lipids cholesterol and cortisone into Pellethane 2363, a polyurethane used in biomedical implants. The method uses refractometry and ultraviolet diode-array detection, with tetrahydrofuran as the mobile phase. Using an injection volume of 150 microliters, the lower limit of accurate measurement for cholesterol (refractive index detection) was 6 micrograms/ml with a lower limit of detection, based on a 2:1 signal-to-noise ratio, of 0.15 micrograms (1 microgram/ml). For cortisone (ultraviolet detection), the lower accurate limit was 0.6 micrograms/ml with a lower limit of 0.015 micrograms (0.1 micrograms/ml). The results show that after 44 h, 2037 micrograms/g cholesterol and 3131 micrograms/g cortisone were absorbed by the polyurethane. The method eliminates extensive sample manipulation and is sensitive to low levels of lipid in the presence of a high-molecular-mass synthetic polymer.
Absorption↗
An automatic interference refractometer.
Interference refractometry is a well-established method of determining the concentration of anaesthetic agents in gas mixtures. A photo-electric detector system has been fitted to a small portable, direct-reading interference refractometer to display automatically the concentration of the agent being measured. The design of the instrument is described and two possible methods of information display are suggested.
Anesthetics↗
The clinical refractometer: a useful tool for the determination of specific gravity and osmolality in canine urine.
For the determination of specific gravity of canine urine the urinometer is often used. An alternative method is based on refractometry. Both methods were compared and a table for converting refractometer values to urinometer values is given. The refractometer was also compared with an osmometer. A linear relation was found between the readings of both instruments. The results clearly indicate that the refractometric method is very suitable for the small animal practitioner. The instrument appears to be a good alternative for both the urinometer and the osmometer.
Animals↗
A human model of allergic conjunctivitis.
Using the method of refractometry to measure protein concentration in tears, a simple model was developed to evaluate the allergic response in humans. Timothy grass pollen was instilled into the cul de sac of a human subject, and the protein content of the subject's tears was sampled every 15 minutes for three hours. Once the time course of this experiment was predictable, various eye medications were instilled into the subject's eye 30 minutes after allergic challenge. It was noted that 1.0% and 0.1% prednisolone, each combined with 0.12% phenylephrine hydrochloride, as well as 1% epinephryl borate eye drops, produced an almost immediate return to normal of tear protein levels, whereas 1.0% medrysone, 0.1% fluorometholone, 1.0% prednisolone, and 0.12% prednisolone had less pronounced effects on reduction of elevated tear protein concentration.
Administration, Topical↗
Outflow facility and its response to pilocarpine decline in aging rhesus monkeys.
Refractive error and total outflow facility were determined by Hartinger coincidence refractometry and two-level constant-pressure perfusion, respectively, in 17 rhesus monkeys, aged 5 to 29 years. Maximum accommodative response to corneal (iontophoretic) carbachol hydrochloride, baseline outflow facility, and the facility response to strong but submaximal intracameral doses of pilocarpine hydrochloride all declined with age. The correlation between accommodative response to carbachol and facility response to pilocarpine was slightly stronger than that between age and facility response. Since the ciliary muscle plays a major role in controlling both outflow facility and accommodation, and since histologic and videographic techniques demonstrate an age-related decline in rhesus ciliary muscle excursion induced by topical pilocarpine or electrical stimulation of the Edinger-Westphal nucleus, the present data support the hypothesis that an age-related decline in ciliary muscle mobility is associated, perhaps causally, with an age-related decline in facility and facility responsiveness to cholinergic drugs.
Accommodation, Ocular↗
Lamellar keratoplasty in keratoconus.
The authors present the results of 11 keratoplasties in cases of keratoconus, comparing the visual acuity and the ocular refraction before and after the operation (ophtalmometry, objective and subjective refractometry). The statistical data indicate a meaningful flattening of the corneal curvature (12.84 dpt average) and a mean reduction of the myopia for 8.227 dpt. In fact, the basic regular astigmatism of the cornea had not been altered. The mean visual acuity was 0.68 (with an improvement of 0.495). No further damage of acuity had been observed. After 10 to 69 months a medical checkup revealed transparent grafts in five cases; four presented small maculae; one, thin folds of Descemet's membrane. Based on the authors' experience and on the literature, the paper recommends lamellar keratoplasty in cases of keratoconus, the surgeon must choose the appropriate moment in the course of the development of this disease.
Adult↗
High performance liquid chromatographic separation of diacylglycerol acetates to quantitate disaturated species of lung phosphatidylcholine.
A high-performance liquid chromatographic (HPLC) separation of diacylglycerol acetates to quantitate disaturated species of lung phosphatidylcholine (PC) was studied. The diacylglycerol acetates were applied on a reversed phase column, eluted by an isocratic solvent, acetonitrile/isopropanol/water (35:15:1, v/v/v) at a flow rate of 1 ml/min, and detected by differential refractometry (RI). This isocratic HPLC method was useful to separate disaturated species from the others of lung PC. The quantitative analysis of the molecular species separated by HPLC was studied by RI detection. Chromatograms obtained by RI detection and radioactivity determination of diacylglycerol [3H]acetates prepared by [3H]acetic anhydride were almost identical. The RI detector responded in the same degree for different authentic standards of diacylglycerol acetates. The detection limit with RI detection was about 30 nmoles. Molecular species of PCs from human lung and carcinoma tissues were analyzed by this HPLC method. The contents of disaturated species were very similar to those reported previously. These results indicate that RI detection is very useful in the nmole range for the quantitative analysis among the molecular species containing disaturated species.
Acetates↗
Functional morphology of accommodation in the raccoon.
The raccoon (Procyon lotor) is a small carnivore which eats in the upright position, using hand- and finger-like front paws and digits to wash, hold and examine its food at close range. These anatomic and behavioral characteristics prompted structural and functional studies of the accommodative capability of this species. By light and electron microscopy, we observed a prominent ciliary smooth muscle and zonular apparatus. When stimulated by carbachol or pilocarpine, the muscle and zonular apparatus exhibited a shift from longitudinal to reticular or circular orientation of some ciliary muscle bundles, anterior movement of the muscle as a whole, and more oblique crossing of the zonular fiber bundles in the zonular plexus. Maximum carbachol-induced accommodative amplitude measured by coincidence refractometry ranged from 3 to 19 diopters in these 1 to 9 yr old animals, with no definite age-accommodation relationship. A-scan ultrasonographic biometry showed that during accommodation the lens thickened very little, if at all, but moved anteriorly, while the apparent cornea to retina distance increased slightly. The raccoon thus exhibits the greatest accommodative capability of any non-primate terrestrial mammal so far studied.
Accommodation, Ocular↗