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Results for “Refractometry”

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At least 145 records · Page 8Linked to original sources
PubMed1978

[Refractometric measurement of total serum protein, comparison of refractometry and biuret test (author's transl)].

Study on the Refractometric Determination of Total Protein in Serum, Comparison of the Refractometric and Biuret Method. Total protein concentration in serum was determined by the aid of the Abbé-refractometer and the biuret method. Both methods showed a good precision and accuracy. The investigation was carried out in 241 sera with normal bilirubin (up to 1 mg/100 ml), cholesterol (up to 200 mg/100 ml) and urea (up to 23,0 mg/100 ml) concentration, in 43 sera with increased (10,6-26,6 mg/100 ml) bilirubin concentration, in 129 sera with increased (200-520 mg/100 ml) cholesterol concentration and in 43 sera with increased (23,0-155,3 mg/100 ml) urea concentration. The comparison of the refractometric values with the values obtained by the biuret method in the 241 sera with normal bilirubin, cholesterol and urea concentration (correlation coefficient = 0,971) showed a close correlation and in the 43 sera with increased bilirubin concentration (correlation coefficient = 0,958) an acceptable correlation. However no close correlations were observed in the 129 sera with increased cholesterol concentration and in the 43 sera with increased urea concentration. The correlation lines diverged proportional with the increase of cholesterol and urea concentration from the expected correlation lines.

Bilirubin↗
PubMedDate not supplied

[The potentials of laser refractometry in selecting the eyeglass correction in astigmatism].

Based on the results of clinical trials of a new commercial laser analyzer LAR-2, the author developed a method for laser specification of astigmatic refraction with the use of this device. The method helps adequately solve the principal refraction problem, specify the optimal eyeglass correction for patients with astigmatism. A conclusion is made on diagnostic fitness of LAR-2 laser analyzer.

Adolescent↗
PubMed1997

Comparison of objective methods for quantifying the refractive effect of photo-astigmatic refractive keratectomy using the MEL-60 excimer laser.

PURPOSE: To investigate the accuracy and precision of automated keratometry, automated refractometry, and computerized corneal topography in estimating the subjective refractive outcome of photo-astigmatic refractive keratectomy six months postoperatively. METHODS: Photo-astigmatic refractive keratectomy (Aesculap-Meditec, MEL-60 Excimer Laser) was performed on 26 eyes with a preoperative myopia ranging from -4.0 to 7.6 dioptres, and a naturally occurring astigmatism from 0.75 to 5.0 dioptres. Six months postoperatively refractive outcome was evaluated by automated keratometry, automated refractometry (Nikon NRK-8000), computerized topography (TMS-1), and subjective refraction. Estimate errors were computed as the difference between the change in subjective refraction and the change in automated keratometry, automated refractometry, and surface topography, respectively. Astigmatic changes were evaluated by the second harmonic component in the Fourier series analysis. RESULTS: Subjective spherical as well as cylindrical values were reduced significantly six months postoperatively. The estimate error (mean +/- one standard deviation) for automated keratometry was -1.26 +/- 0.72 dioptres for the spherical equivalent and -1.36 +/- 1.02 dioptres for the cylinder; for automated refractometry it was -0.78 +/- 0.91 dioptres for the spherical equivalent and -0.66 +/- 0.92 dioptres for the cylinder. The best estimates of subjective changes were obtained when the average of ring 2 and 3 of the topographic data was used: -0.15 +/- 0.82 dioptres for the spherical equivalent and -0.78 +/- 0.80 dioptres for the cylinder. CONCLUSIONS: The computerized topographer with the Fourier analysis was superior to automated keratometry and automated refractometry in estimating the subjective spherical refractive outcome and comparable to automated refractometry in estimating the subjective cylinder refractive outcome after photo-astigmatic refractive keratectomy.

Adult↗
PubMed2003

Comparison of 3 Methods to Assess Urine Specific Gravity in Collegiate Wrestlers.

OBJECTIVE: To investigate the reliability and validity of refractometry, hydrometry, and reagent strips in assessing urine specific gravity in collegiate wrestlers. DESIGN AND SETTING: We assessed the reliability of refractometry, hydrometry, and reagent strips between 2 trials and among 4 testers. The validity of hydrometry and reagent strips was assessed by comparison with refractometry, the criterion measure for urine specific gravity. SUBJECTS: Twenty-one National Collegiate Athletic Association Division III collegiate wrestlers provided fresh urine samples. MEASUREMENTS: Four testers measured the specific gravity of each urine sample 6 times: twice by refractometry, twice by hydrometry, and twice by reagent strips. RESULTS: Refractometer measurements were consistent between trials (R =.998) and among testers; hydrometer measurements were consistent between trials (R =.987) but not among testers; and reagent-strip measurements were not consistent between trials or among testers. Hydrometer (1.018 +/- 0.006) and reagent-strip (1.017 +/- 0.007) measurements were significantly higher than refractometer (1.015 +/- 0.006) measurements. Intraclass correlation coefficients were moderate between refractometry and hydrometry (R =.869) and low between refractometry and reagent strips (R =.573). The hydrometer produced 28% false positives and 2% false negatives, and reagent strips produced 15% false positives and 9% false negatives. CONCLUSIONS: Only the refractometer should be used to determine urine specific gravity in collegiate wrestlers during the weight-certification process.

Journal Article↗
PubMed1990

[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↗
PubMedDate not supplied

Evaluation of 3 assays for failure of passive transfer in calves.

This study examined the sensitivity, specificity, predictive values, and classification accuracy of 3 commonly used screening tests for failure of passive transfer: the sodium sulfite turbidity test, the zinc sulfate turbidity test, and refractometry relative to serum immunoglobulin G1 (IgG1) concentrations determined by radial immunodiffusion. Serum samples were obtained from 242 calves ranging from 1 to 8 days of age. Using a serum concentration of 1,000 mg/dL IgG1, to define adequate passive transfer, the zinc sulfate test had a sensitivity of 1.00 and a specificity of 0.52 in the detection of inadequate passive transfer. The endpoint of the test appeared to be higher than desired; calves testing negative had mean serum IgG1 concentration of 955 mg/dL and a large proportion of calves with adequate passive transfer were misclassified as positive for failure of passive transfer. Using the qualitative zinc sulfate test, the percentage of calves correctly classified with regard to passive transfer status was less than that observed with either the sodium sulfite test or refractometry. The sensitivity of the sodium sulfite assay was 0.85 at a 1+ endpoint and 1.00 at a 2 or 3+ endpoint. The specificity of the sodium sulfite assay varied from 0.87 at a 1+ endpoint and 0.56 at a 2+ endpoint. The sensitivity and specificity of refractometry varied from 0.01 to 1.00 depending on the choice of endpoint. Refractometry correctly classified the largest proportion of calves with regard to their passive transfer status at test endpoints of 5.0 and 5.5 g/dL, 83% and 82% respectively. The highest percentages of calves correctly classified occurred with the sodium sulfite test using a 1+ endpoint (86.30%) and refractometry using a 5.0 g/dL endpoint (83.00%). A regression equation was developed that permitted calculation of an optimal endpoint for refractometric determinations of total serum protein concentration. A serum protein concentration of 5.2 g/dL was equivalent to 1,000 mg/dL serum IgG1. Optimal selection of tests for passive transfer status in calves will be governed by the prevalence of failure of passive transfer, test performance, and the anticipated costs of classification errors.

Analysis of Variance↗