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Biomedical subjects

A Turpin

Publications and source records attributed to A Turpin.

At least 19 recordsLinked to original sources
PubMed2006

Do migraineurs have difficulty judging direction of simulated heading?

Some migraineurs have increased thresholds for the detection of global dot motion. We investigated whether migraineurs show consequential abnormalities in the determination of direction of self-motion (heading) from simulated optic flow. The ability to determine heading from optic flow is likely to be necessary for optimal determination of self-motion through the environment. Twenty-five migraineurs and 25 controls participated. Global dot motion coherence thresholds were assessed, in addition to performance on two simulated heading tasks: one with a symmetrical flow field, and the second with differing velocity of optic flow on the left and right sides of the participant. While some migraineurs demonstrated abnormal global motion coherence thresholds, there was no difference in performance on the heading tasks at either simulated walking (5 km/h) or driving (50 km/h) speeds. Increased global motion coherence thresholds in migraineurs do not result in abnormal judgements of heading from 100% coherent optic flow.

Adolescent↗
PubMed2003

Measurement error of visual field tests in glaucoma.

AIM: Psychophysical strategies designed for clinical visual field testing produce rapid estimates of threshold with relatively few stimulus presentations and so represent a trade-off between test quality and efficiency. The aim of this study was to determine the measurement error of a staircase algorithm similar to full threshold with standard automated perimetry (SAP) and frequency doubling perimetry (FDP) in glaucoma patients. METHODS: Seven patients with early open angle glaucoma (OAG) were prospectively recruited. All were experienced in laboratory based psychophysics. Three matched test locations were examined with SAP (externally driven Humphrey field analyser) and FDP (CRT) in a single arbitrarily selected eye of each subject. Each location was tested twice with a 4-2-2 dB staircase strategy, similar to full threshold, and then with the method of constant stimuli (MOCS). Accuracy (threshold estimation error) was quantified by determination of differences between "true" threshold measurements made by MOCS and single staircase threshold estimates. Precision (repeatability) was quantified by the differences between repeated staircase threshold estimates. RESULTS: Precision was relatively high for both tests, although higher for FDP than SAP at depressed sensitivity levels. The staircase strategy significantly underestimated threshold sensitivity for both test types, with the mean difference (95% CI) between staircase and MOCS thresholds being 4.48 dB (2.35 to 7.32) and 1.35 dB (0.56 to 1.73) for SAP and FDP respectively. Agreement levels (weighted kappa) between MOCS and staircase thresholds were found to be 0.48 for SAP and 0.85 for FDP. Although this "bias" appeared constant for FDP across all sensitivity levels, this was not the case for SAP where accuracy decreased at lower sensitivity levels. CONCLUSION: Estimations of threshold sensitivity made using staircase strategies common to clinical visual field test instrumentation are associated with varying degrees of measurement error according to visual field test type and sensitivity. In particular, SAP significantly overestimates the "true" level of sensitivity, particularly in damaged areas of the visual field, suggesting that clinical data of this type should be interpreted with caution.

Aged↗
PubMed2001

Variability components of standard automated perimetry and frequency-doubling technology perimetry.

PURPOSE: To evaluate and compare intra- and intertest variability components for both standard automated perimetry (SAP) and frequency-doubling technology (FDT) perimetry in a small group of normal individuals and patients with glaucoma. METHODS: The method of constant stimuli (MOCS) was used to examine matched test locations with both SAP and FDT perimetry stimuli in a group of eight normal individuals and seven patients with glaucoma. Subjects were tested weekly at three predetermined visual field loci for 5 consecutive weeks. Frequency-of-seeing (FOS) curves were generated and used to quantify threshold sensitivity (50% seen on FOS, in decibels), intratest variability (FOS interquartile range, in decibels), and intertest variability (interquartile range of weekly repeated threshold determinations, in decibels). RESULTS: In patients with glaucoma, SAP intra- and intertest variabilities were found to increase with sensitivity reductions, as previously reported. FDT perimetry revealed that both intra- and intertest variability components did not appreciably change with reductions in sensitivity. With the measurement scales used in this investigation, both intra- and intertest variability components were significantly greater for SAP than for FDT perimetry (P < 0.001 and P = 0.003, respectively). Intratest variability exceeded intertest variability for both SAP (P = 0.001) and FDT perimetry (P < 0.001). CONCLUSIONS: For both SAP and FDT perimetry, variability occurring within a single test session contributed more to total variability than between-session variability. When the measurement scales available on commercial instrumentation were used, FDT perimetry exhibited significantly less variability than SAP, especially within regions of visual field sensitivity loss. FDT perimetry therefore shows promise as an effective test for detecting progressive glaucomatous visual field loss, although prospective longitudinal validation is still required to determine sensitivity to change.

Adult↗
PubMed1978

[Investigation of the immunity status towards tetanus of a population of mechanics at the car-factory "Renault" (author's transl)].

Tetanus immunity has been studied in a population of mechanics working at the car-factory "Renault". For the study, 283 individuals were divided into 3 groups. The first group consisted of non-vaccined individuals, the second of vaccinated individuals and the third of individuals who had been boostered. The influence of different parameters on tetanus immunity status was considered, i. e. the age of the subjects, the time at which boostering was given, the serotherapy (when it was administered) and the contact with machine lubricating and cooling fluids. Clostridium tetani bacilli and spores were frequently found in aqueous machine fluids. Their presence is a potential hazard for non-vaccinated mechanics coming to contact with the fluids. Tetanus antibody levels in the sera of the tested population were determined in vivo by the toxin neutralization test. The influence on tetanus immunity of the different parameters considered in this paper was subjected to statistical analysis. From the whole population, 27% of the individuals were found to have no protection against tetanus. When age was taken into account, 53% of the individuals over 45 years old and 10% of those under 45 years old were shown to be devoid of tetanus immunity. It could be shown that younger individuals were better protected than older ones, because the formers had been immunized with adsorbed tetanus toxoid and most of the latters with fluid toxoid. Of the individuals in the third group who had received a booster injection within 15 years after primo-vaccination, 98% showed protective tetanus antibody levels in their sera in contrast to 25% when boostering had occurred more than 15 years after primo-vaccination. Contact with machine fluids was found to influence the degree of immunity of only those individuals whose boostering dated back to more than 25 years. Unexpectedly, 3 mechanics seemed to develop immunity after coming into contact with machine fluids. From the results reported here, it is concluded that tetanus immunity in vaccinated individuals should be renewed by a compulsory booster injection given every 5, 10 or, at the minimum, 15 years. Moreover, high-risk populations such as that represented by the mechanics should be immunized or boostered on commencing employment.

Adult↗
PubMed1978

[Antitetanus vaccination: preliminary results of a study in Africa].

Two commercialized anatoxins, titrating 30 Lf per dose and adsorbed on Ca phosphate and Al hydroxide respectively, were studied in comparison with an experimental anatoxin titrating 25 Lf per dose and adsorbed on Al phosphate, and with a placebo. 595 schoolchildren from Cameroun were randomly assigned to four groups and inoculated twice, with a year's interval between the two inoculations. Serological checks were carried out by double-blind trials using the passive hemagglutination (HA) method on days 7, 90, 365 and 395. HA titers rose substantially after three months and then fell during the 12th month. The HA method does not give a clear indication of the amount of protection obtained after only one inoculation, but this amount would seem to be small according to the results of neutralization tests carried out on samples. It is only after the second injection that protection is provided for most subjects. Results vary depending on the anatoxin and are not linked to the--benign--clinical reactions observed. This study confirms that if anatoxins with high antigenicity are to be used, two injections are necessary and sufficient to guarantee good immunity protection.

Adolescent↗
PubMed1975

Titration of antibodies to tetanus toxoid by agglutination of purified tetanus toxoid sensitized latex particles.

The method of sensitized latex particle agglutination which we have devised allows the selection of samples of plasma for the preparation of immunoglobulins. The population of thus selected samples is the same as is selected by the in vivo test, having a titer greater than or equeal to 6 IU/ml. The test gives a clear-cut difference between the positive and negative results and does not give any prozone phenomenon. It can be used extensively, as the batches of sensitized latex particles may be stored for quite a long time.

Adult↗