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At least 73 records · Page 4Linked to original sources
PubMed1998

Correlation between anterior chamber IgG/albumin concentrations and laser flare photometry in eyes with endogenous uveitis.

PURPOSE: To assess the correlation between laser flare measurements and anterior chamber IgG/albumin concentrations in eyes with mild to severe inflammation. MATERIALS AND METHODS: Seventeen eyes of 17 patients with endogenous uveitis underwent diagnostic paracentesis. IgG and albumin concentrations were determined from the samples of aqueous humor. Laser flare measurements were performed 1 h prior to paracentesis. The relationship between flare measurements and IgG/albumin concentrations was studied be plotting the data on a logarithmic scale. RESULTS: The flare measurement was 97.5+/-150.0 photons ms (mean +/- SD; range 4.3-528.7). The IgG concentration was 41.0+/-51.4 mg/dl mean +/- SD; range 0.2-200). The albumin concentration was 184.6+/-196.2 mg/dl (mean +/- SD; range 4-535). When plotted on a logarithmic scale, there was a statistically significant linear relationship between the flare measurements and the anterior chamber IgG or albumin concentrations (y = 1.14x-0.64, r= 0.87, p<0.001 for IgG; y = 1.39x-0.1, r= 0.94, p<0.001 for albumin). CONCLUSION: Laser flare photometry is an accurate technique for assessing anterior chamber inflammation. Flare measurements strongly correlate with blood-aqueous barrier breakdown.

Adolescent↗
PubMedDate not supplied

Correlation study of two methods for evaluating corneal endothelial damage in vitro: the Janus green photometry technique versus cell counting.

Counting of endothelial cells after vital staining is a time-consuming method which, in addition, requires considerable experience and does not normally allow for the study of the entire endothelial cell surface. However, the Janus green photometry technique (JGPT) is an objective, time- and personnel-saving procedure which also has the advantage of allowing for the evaluation of the whole endothelial cell surface. A comparative simultaneous experimental study of the two methods had not been reported. Freshly excised pig corneas (n = 58) were preserved in MK storage medium for 4, 7, 14 and 20 days at 4 degrees C. All corneas were stained with Janus green and alizarin red. A 7-mm corneal button corresponding to an endothelial surface of 38.46 mm2 was punched out. The percentage of damaged cells was determined with cell counting (CC) and with JGPT, and the results were statistically compared. Two methods for CC were used. Cells were counted either directly under the microscope or in photomicrographs. The overall correlation between the results of CC and JGPT was R = 0.98. However, when endothelial cell damage was higher than 30%, CC became an estimation by approximation, since necrotic areas were confluent, whereas with JGPT the results were usable even when the damage was 100%. Thus it appears that although the two methods can be used interchangeably, JGPT may in some instances be the method of choice.

Animals↗
PubMed2002

Estimates of L:M cone ratio from ERG flicker photometry and genetics.

Estimates of L:M cone ratio for males with normal color vision were derived using the flicker-photometric electroretinogram (ERG). These were obtained by best fitting ERG spectral sensitivity functions to a weighted sum of long (L)- and middle (M)-wavelength-sensitive cone spectral absorption curves. Using the ERG, measurements can be made with extremely high precision, which leaves variation in the wavelength of maximal sensitivity (lambda(max)) of the cone photopigments as the major remaining source of inaccuracy in determining the ratio of cone contributions. Here that source of inaccuracy was largely eliminated through the use of individualized L-cone spectral absorption curves deduced from L-pigment gene sequences. The method was used on 62 normal males as part of an effort to obtain a true picture of how normal variations in L:M cone ratio are distributed. The percentage of L cones in the average eye was 65%L [where %L = 100 X L / (L+M)]. There were huge individual differences ranging from 28%-93%L, corresponding to more than a 30-fold range in L:M ratio (0.4-13). However, the most extreme values were relatively rare; 80% of the subjects fell within +/-15 %L of the mean, corresponding to a 4-fold range in L:M ratio (1-4). The method remedies major weaknesses inherent in earlier applications of flicker photometry to estimate cone ratio; however, it continues to depend on the assumption that the average L cone produces a response with an identical amplitude to that of the average M cone. A comparison of the ERG results with the distribution of cone ratios estimated from cone pigment messenger RNA in cadaver eyes indicates that the assumption generally holds true. However, there may be a small number of exceptions in which individuals have normally occurring (but relatively rare) amino acid substitutions in one of their pigments that significantly affect the physiology of the cone class containing that pigment, so as to reduce the amplitude of its contribution to the ERG. Consistent with this possibility, extreme cone contribution ratios were found to be associated with atypical L-pigment amino acid combinations.

Adolescent↗
PubMed2004

Macular pigment measurement by heterochromatic flicker photometry in older subjects: the carotenoids and age-related eye disease study.

PURPOSE: To develop a standardized protocol for measuring macular pigment optical density (MPOD) of experimentally naïve subjects by heterochromatic flicker photometry (HFP). METHODS: MPOD in eyes of 54 women, age 50 and 79 years (mean, 66), was studied. The spatial profile of MPOD was measured in the right eye, and two spatial points were also measured in the left eye. Forty-eight of these inexperienced subjects completed the protocol on two separate visits. For a subset of the group, the MPOD at two different wavelengths was measured. RESULTS: The test-retest correlation at 0.5 degrees eccentricity in the right eye was 0.9. On the second visit, more than 90% of the subjects were able to perform the HFP test with results that were consistent with the absorption spectrum of macular pigment. On the first visit, data from the inexperienced subjects deviated more from the expected relationships between the two wavelengths, presumably because they had less skill in performing the task. However, subjects with high or low macular pigment density were distinguished clearly. CONCLUSIONS: Reliable and meaningful measurements of macular pigment density in older subjects can be made using HFP, with a standardized protocol in the limited time available in large epidemiologic studies. This protocol will be made freely available to other researchers on request.

Aged↗
PubMed2005

Measurement of macular pigment: Raman spectroscopy versus heterochromatic flicker photometry.

PURPOSE: There are several techniques for measuring macular pigment (MP) in vivo, of which Raman spectroscopy (RS) is a recently developed objective METHOD: This study reports the reproducibility, test-retest variability, and validity of RS MP readings, by comparing them with heterochromatic flicker photometry (HFP). METHODS: MP was measured with HFP and RS in 120 healthy subjects, and the latter technique was also used on two separate occasions in a sample of 20 subjects to investigate the intersessional variability of readings. Intrasessional reproducibility of RS MP measurements was also calculated. In addition, serum concentrations of lutein (L) and zeaxanthin (Z) were measured and correlated with both RS and HFP MP readings. RESULTS: Mean (+/-SD) MP in the right eye was 0.279 +/- 0.145 and 0.319 +/- 0.155 with RS and HFP, respectively. The differences between corresponding MP readings taken on RS and HFP lay within the Bland-Altman 95% limits of agreement for the two instruments in 93.6% and 94.4% of cases in the right and left eyes, respectively. Intrasessional reproducibility of RS readings, expressed as the coefficient of variation, was 8.42% +/- 7.12%. Ninety-five percent of MP readings taken with RS on two separate occasions lay within the 95% limits of agreement for the two sessions. A positive, but insignificant, relationship was observed between RS and HFP MP readings and serum concentrations of L and Z (RS, P = 0.356; HFP, P = 0.540). CONCLUSIONS: RS, an objective method of measuring MP levels in vivo, exhibits acceptable reproducibility and test-retest variability. The results demonstrated good correlation between RS and HFP measurements of MP, thus authenticating RS against a validated psychophysical technique of measuring MP. However, investigators should use only one of these instruments for the duration of any given study because of differences in the scientific rationale, and the factors that influence RS and HFP measurements of MP.

Adult↗
PubMed1974

An inexpensive system of automated flame photometry of serum sodium and potassium.

An inexpensive automated flame photometry system has been produced by utilising an I.L. 143 flame photometer fitted with an analogue output connected to a sampler (Auto Analyzer or other). The pump of the I.L. 144 dilutor is used to aspirate the sample and a variety of single or two pen recorders can be used to record the results at the rate of 60 specimens an hour.

Autoanalysis↗
PubMed1979

Multiangle light scattering flow photometry of cultured human fibroblasts: comparison of normal cells with a mutant line containing cytoplasmic inclusions.

Multi-angle light scattering flow photometry was used to study the light scattering properties of normal cultured fibroblasts and a mutant fibroblast line containing cytoplasmic lysosomal inclusions. The effect of glutaraldehyde fixation on the light scattering properties of the cells was also examined and correlated with their ultrastructure. Normal fibroblasts showed uniform organelle distribution with few vacuoles or dense bodies in the cytoplasm while the mutant line showed abnormal cytoplasmic inclusions of varying morphology, density and lucency. As predicted by light scattering theory, the mutant cells containing the cytoplasmic inclusions scattered more light at large angles (greater than theta = 1.85 degrees) than did the normal cells. Glutaraldehyde fixation decreased light scattering at small angles (less than theta = 1.85 degrees), increased light scattering at larger angles (greater than theta = 1.85 degrees) in both normal and mutant cells and enhanced resolution of the light scattering signatures. The mutant line scattered 2-3 times more light at a wide angle (greater than theta = 12.74 degrees) than did the normal cells. These data suggest that abnormal lysosomal storage inclusion bodies in the cytoplasm of the cells can be detected by differential light scattering methods.

Cell Line↗
PubMed1983

Linearity law reexamined for flicker photometry by the summation-index method.

The summation-index technique was applied to flicker photometry to investigate the linearity law. Two test stimuli of different wavelengths were mixed, and the luminous efficiency of the mixture was measured under three different adapting conditions: no adaptation, 507-nm adaptation, and 650-nm adaptation. Most of the wavelength combinations and adapting conditions gave a summation index of 0.30, which is the linearity in the visual system that is responsible for the flicker perception, namely, the achromatic channel. An exception was the red and green combination under the no-adaptation condition, which gave a slightly smaller summation index than 0.30, indicating that these two stimuli do not add linearly. The subsummation was interpreted as cancellation of red and green responses in the red-versus-green opponent channel. The subsummation disappeared when the flicker frequency was increased from 5 to 12 Hz, confirming the interpretation.

Adaptation, Physiological↗
PubMed1993

Red-green flicker photometry and nonlinearities in the flicker electroretinogram.

We investigated whether responses from different cone classes are combined before or after the nonlinearity that is responsible for generating nonlinear response components of the flicker electroretinogram (ERG). We measured the nonlinear response of the retina while systematically varying the modulation in the long-wavelength-sensitive and middle-wavelength-sensitive cones by changing the proportions of flickering 633- and 543-nm lights that compose a sum-of-sinusoids temporal waveform. We found that at high temporal frequencies the ERG responses are best accounted for by a model in which the principal retinal nonlinearity is located before the convergence of signals from the two cone classes. At low temporal frequencies the ERG signal is dominated by cone-antagonistic responses. At frequencies of 30 Hz and higher, the flicker ERG and psychophysical flicker photometry give similar estimates of the relative proportions of long- and middle-wavelength-sensitive cones. The ERG photometric null is frequency dependent, whereas the psychophysically determined ratio is much less sensitive to changes in frequency.

Color Perception↗
PubMed1994

Spectral efficiency across the life span: flicker photometry and brightness matching.

Spectral efficiency functions were measured for 50 color-normal observers (aged 19-85 years) by means of heterochromatic flicker photometry (HFP) and heterochromatic brightness matching (HBM). Foveally viewed, circular, 1.2 degrees-diameter stimuli were presented as 3-s flashes (50% duty cycle) in Maxwellian view. Monochromatic lights (420-700 nm; 16 wavelengths) were equated to a 100-Td (trolands), broadband white standard in both procedures. In both HFP and HBM, average sensitivity (specified at the cornea) decreased at short wavelengths with increasing age, consistent with age-related increases in the density of the ocular media. The short-wavelength HBM decline was of lower magnitude than the HFP decline. HFP data were modeled by a weighted additive combination of long- and middle-wavelength-cone inputs and density spectra of the ocular media and macular pigment. HBM data were analyzed with an upper envelope of additive and subtractive combinations of log-transformed cone absorption functions. These analyses indicated that HBM sensitivity, specified at the retina by correction for estimated lens and macular pigment density, increased with age in an approximately wavelength-independent manner over a broad range from 420 to 560 nm.

Adult↗
PubMed1996

Electroretinogram flicker photometry and its applications.

The electroretinogram (ERG) has been a traditional tool for the measurement and the analysis of spectral sensitivity. With the appropriate choices of stimulus and measurement conditions, the ERG permits a noninvasive examination of photopigment complement and provides the means for studying the combination of spectral signals at various locations throughout the retina. There are a number of practical problems associated with making spectral measurements with the ERG. One approach to minimizing these problems is to exploit the advantages of a flicker-photometric procedure. We summarize a method used to conduct ERG flicker photometry and illustrate a range of problems to which this technique can be successfully applied.

Electroretinography↗
PubMed2005

Induction effects for heterochromatic brightness matching, heterochromatic flicker photometry, and minimally distinct border: implications for the neural mechanisms underlying induction.

Brightness induction refers to the finding that the apparent brightness of a stimulus changes when surrounded by a black versus a white stimulus. In the current study, we investigated the effects of black/white surrounding stimuli on settings made between red and green stimuli on three different tasks: heterochromatic brightness matching (HBM), heterochromatic flicker photometry (HFP), and minimally distinct border (MDB). For HBM, subjects varied the relative luminance between the red and green stimuli so that the brightness of the two colors appeared equal. For the two other tasks, matches were made based on minimizing red/green flicker (HFP) or the saliency of a red/green border (MDB). For all three tasks, the presence of black/white surrounding stimuli significantly altered red/green settings, demonstrating the existence of induction effects. These results are discussed in terms of which underlying color pathways (L+ M versus L-M) may contribute to induction effects for the different tasks.

Adaptation, Ocular↗
PubMed1992

Quantification of islet cell antibodies by microscope photometry and antibody titration compared.

Islet cell antibodies can predict eventual insulin-dependent diabetes mellitus. In the standard method used by the Immunology of Diabetes Workshop (IDW), predictive power depends on antibody titer as determined by testing multiple serum dilutions. Here I report use of a microscope-based photometry system (MPS) to test whether islet fluorescence intensities from undiluted sera can predict IDW results. MPS testing of 120 undiluted IDW specimens correctly identified 27 of 31 positive and 84 of 89 negative specimens. The relationship between IDW consensus values and MPS readings of undiluted sera is: IDW = 2.45 MPS - 1.44 (r = 0.67, P less than 0.001). Thus, corrected islet intensities from undiluted sera correlated well with IDW values. However, the ability of MPS to predict high IDW consensus values is limited, which may reflect the variable antigenic content of pancreas specimens; moreover, background correction as currently applied is incomplete; nonspecific immunofluorescence appears to emanate from within the islet.

Autoantibodies↗
PubMedDate not supplied

[Use of methods of derivative conductometry and photometry for assessing the structure of a cellular suspension].

Experimental proofs for the possibility of studying the dynamical structure of rotatory moving erythrocyte suspension with the methods of derivative conductometry and photometry are presented. The amplitude of the recorded impulses was proportional to the cell concentration and the angle velocity, and strongly depended on the shape of the suspended cells.

Cell Movement↗
PubMedDate not supplied

[Recording the results of the indirect hemagglutination reaction in the microanalysis class by using vertical photometry].

A two-channel photometer is experimentally found to be suitable for vertical photometry to record the output of indirect hemagglutination, which is detected by the type of precipitates deposited on a parabolic bottom of sockets in microtitrimetric plane tables. Dynamic processes of depositing are studied as a function of sample volume and concentration of erythrocytic diagnosticum.

Evaluation Studies as Topic↗
PubMed1985

[Determination of the number of pathogens in bacterial suspensions using laser nephelometry in comparison to the photometry and plate counting method].

We determined the number of bacteria in suspensions of three bacterial species (S. aureus ATCC 25923, E. coli ATCC 25922, P. aeruginosa ATCC 27853) in liquid medium using two optical methods - laser-nephelometry and photometry. These results were compared with the CFU/ml determined by the agar plate test in each suspension. Further we defined the applicable range of measurement of both optical methods. The calculated factor of correlation (r = 0.99) attested the very good conformity of the results obtained by both optical methods. The determination of the number of bacteria in suspensions by laser-nephelometry is a simple though very sensitive method. The results can well be reproduced. A further advantage of this method is the immediate information about the number of bacteria in suspension. All these facts recommend laser-nephelometry as a method useful in any bacteriological routine laboratory for determination of the number of bacteria in suspensions.

Bacteriological Techniques↗
PubMed1979

[Comparison of ion-selective electrodes and flame photometry for the determination of serum Na+ and K+ for clinical purposes (author's transl)].

The ORION SPACE-STAT (SS-30) and the TECHNICON STAT/ION were used to investigate quality control of Na+- and K+-determinations in test sera (n=8) and in the plasma of 100 patients. The flame photometer IL 543 was used as a reference apparatus. The ion-selective electrode instruments, SS-30 and STAT/ION, gave results very similar to those of flame photometry. The values from the SS-30 were higher by an average of 3% to 5% compared with the values from the other instruments. An explanation for this bias may be the fact that the SS-30 (unlike the STAT/ION and the IL 543) measures electrolyte activities or concentrations in undiluted plasma water. On the basis of these results the routine use of ion-selective electrodes for Na+- and K+-determination can be recommended for clinical laboratories.

Electrodes↗