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This study assesses virologic response, safety, tolerability, and changes in health-related quality of life (HRQoL) in antiretroviral (ARV)-naive patients treated with 2 atazanavir (ATV)-based regimens over 96 weeks. Treatment-naive adult patients (n = 200) were randomized to receive either ATV 300 mg with ritonavir (RTV) 100 mg (ATV300/r, n = 95) or ATV 400 mg (ATV400; n = 105). At week 96, 75% of ATV300/r-treated and 70% of ATV400-treated patients achieved viral loads <400 copies/mL (difference estimate [95% confidence interval, CI] = 5.1 [-7.1 to 17.2]). Five and 20 patients, respectively, experienced virologic failure. Adverse event-related discontinuations occurred among 8% receiving ATV300/r and 3% receiving ATV400. Plasma lipid elevations were generally low. Both regimens were well tolerated and associated with sustained improvements in HRQoL. These findings demonstrate long-term efficacy, tolerability, and safety of both ATV300/r and ATV400 in ARV-naive patients through 96 weeks with improvements in HRQoL.
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Fármacos Anti-VIH/efectos adversos , Fármacos Anti-VIH/uso terapéutico , Infecciones por VIH/tratamiento farmacológico , Oligopéptidos/efectos adversos , Oligopéptidos/uso terapéutico , Piridinas/efectos adversos , Piridinas/uso terapéutico , Ritonavir/uso terapéutico , Adulto , Anciano , Fármacos Anti-VIH/administración & dosificación , Terapia Antirretroviral Altamente Activa , Sulfato de Atazanavir , Farmacorresistencia Viral/genética , Femenino , VIH-1/efectos de los fármacos , Humanos , Masculino , Persona de Mediana Edad , Oligopéptidos/administración & dosificación , Estudios Prospectivos , Piridinas/administración & dosificación , ARN Viral/sangre , Ritonavir/administración & dosificación , Carga Viral , Adulto JovenRESUMEN
We present a fast gas chromatographic system that can be used as a second dimension in comprehensive two-dimensional (supercritical fluid × gas) chromatography (SFC × GC). The temperature of the short (1 m long) capillary column is controlled by a resistively heated coaxial stainless-steel tube. The electrical resistance and, therefore, temperature of the stainless-steel tube are measured by continuous monitoring of the current/voltage ratio. Highly repeatable heating rates of up to 2100 °C min-1 (35 °C s-1) are obtained, which should be high enough for the most demanding fast chromatograms. To reduce the cooling time between temperature programs, the column is cooled by injecting evaporating carbon dioxide into the space between the coaxial heater and the column. This gives cooling rates of 5100 °C min-1 (85 °C s-1), which allows quick succession of temperature programs. More repeatable heating profiles with stable GC retention times together with faster cooling are significant improvements on previous SFC × GC systems. Cycle times of four gas chromatograms per minute could readily be achieved, which allows efficient coupling to high-resolution stop-flow SFC in the first dimension. We demonstrate the fast chromatograph by separating fatty acid methyl esters, yielding information that would be useful in the food and biodiesel industries.
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Cromatografía con Fluido Supercrítico/instrumentación , Calor , Cromatografía de Gases/instrumentación , Cromatografía de Gases/métodos , Cromatografía con Fluido Supercrítico/métodosRESUMEN
Essentials Marzeptacog alfa (activated) [MarzAA] is a novel variant of activated human factor VII. A phase 1 dose escalation trial of MarzAA was conducted in subjects with severe hemophilia. MarzAA was safe and tolerated at intravenous doses up to 30 µg kg-1 Data observed support further trials for hemophilia patients with inhibitors to factors VIII/IX. SUMMARY: Background Marzeptacog alfa (activated) (MarzAA), a new recombinant activated human factor VII (rFVIIa) variant with four amino acid substitutions, was developed to provide increased procoagulant activity and a longer duration of action in people with hemophilia. Objectives To investigate the safety, tolerability, immunogenicity, pharmacokinetics (PK) and pharmacodynamics (PD) of single ascending intravenous bolus doses of MarzAA in non-bleeding patients with congenital hemophilia A or B with or without inhibitors. Methods This international, phase 1, open-label study (NCT01439971) enrolled males aged 18-64 years with severe hemophilia A or B, with or without FVIII or FIX inhibitors. Subjects were assigned to single-dose MarzAA cohorts (0.5, 4.5, 9, 18 or 30 µg kg-1 ). Blood sampling was performed predose and postdose, and subjects were monitored for 60 days postdose. Safety endpoints included adverse events, vital sign changes, electrocardiograms, laboratory abnormalities, and immunogenicity; secondary endpoints included evaluation of PK and PD. Results Overall, in 25 patients, MarzAA was well tolerated at all dose levels tested, and was not associated with dose-limiting toxicity. No treatment-emergent severe or serious adverse events occurred. MarzAA showed linear dose-response PK across the 4.5-30 µg kg-1 dose range, with a terminal half-life of â 3.5 h. Dose-dependent shortening of the activated partial thromboplastin time and prothrombin time, and evidence of an increase in peak thrombin as determined with a thrombin generation assay, were observed at all doses. Conclusions MarzAA was tolerated at doses up to 30 µg kg-1 . The safety profile and pharmacological effects observed support further clinical trials for the treatment of hemophilic patients with inhibitors.
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Coagulantes/administración & dosificación , Factor VIIa/administración & dosificación , Hemofilia A/tratamiento farmacológico , Hemofilia B/tratamiento farmacológico , Administración Intravenosa , Adolescente , Adulto , Coagulantes/efectos adversos , Coagulantes/farmacocinética , Europa (Continente) , Factor VIIa/efectos adversos , Factor VIIa/farmacocinética , Hemofilia A/sangre , Hemofilia A/diagnóstico , Hemofilia B/sangre , Hemofilia B/diagnóstico , Humanos , Masculino , Persona de Mediana Edad , Proteínas Recombinantes/administración & dosificación , Proteínas Recombinantes/efectos adversos , Proteínas Recombinantes/farmacocinética , Índice de Severidad de la Enfermedad , Sudáfrica , Factores de Tiempo , Resultado del Tratamiento , Estados Unidos , Adulto JovenRESUMEN
BACKGROUND: The 2NN Study was a randomised comparison of the non-nucleoside reverse-transcriptase inhibitors (NNRTI) nevirapine and efavirenz. METHODS: In this multicentre, open-label, randomised trial, 1216 antiretroviral-therapy-naive patients were assigned nevirapine 400 mg once daily, nevirapine 200 mg twice daily, efavirenz 600 mg once daily, or nevirapine (400 mg) and efavirenz (800 mg) once daily, plus stavudine and lamivudine, for 48 weeks. The primary endpoint was the proportion of patients with treatment failure (less than 1 log(10) decline in plasma HIV-1 RNA in the first 12 weeks or two consecutive measurements of more than 50 copies per mL from week 24 onwards, disease progression [new Centers for Disease Control and Prevention grade C event or death], or change of allocated treatment). Analyses were by intention to treat. FINDINGS: Treatment failure occurred in 96 (43.6%) of 220 patients assigned nevirapine once daily, 169 (43.7%) of 387 assigned nevirapine twice daily, 151 (37.8%) of 400 assigned efavirenz, and 111 (53.1%) of 209 assigned nevirapine plus efavirenz. The difference between nevirapine twice daily and efavirenz was 5.9% (95% CI -0.9 to 12.8). There were no significant differences among the study groups in the proportions with plasma HIV-1 RNA concentrations below 50 copies per mL at week 48 (p=0.193) or the increases in CD4-positive cells (p=0.800). Nevirapine plus efavirenz was associated with the highest frequency of clinical adverse events, and nevirapine once daily with significantly more hepatobiliary laboratory toxicities than efavirenz. Of 25 observed deaths, two were attributed to nevirapine. INTERPRETATION: Antiretroviral therapy with nevirapine or efavirenz showed similar efficacy, so triple-drug regimens with either NNRTI are valid for first-line treatment. There are, however, differences in safety profiles. Combination of nevirapine and efavirenz did not improve efficacy but caused more adverse events.
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Fármacos Anti-VIH/administración & dosificación , Infecciones por VIH/tratamiento farmacológico , VIH-1 , Nevirapina/administración & dosificación , Oxazinas/administración & dosificación , Inhibidores de la Transcriptasa Inversa/administración & dosificación , Adulto , Alquinos , Fármacos Anti-VIH/efectos adversos , Benzoxazinas , Ciclopropanos , Esquema de Medicación , Quimioterapia Combinada , Femenino , Infecciones por VIH/virología , VIH-1/aislamiento & purificación , Humanos , Masculino , Nevirapina/efectos adversos , Oxazinas/efectos adversos , ARN Viral/sangre , Inhibidores de la Transcriptasa Inversa/efectos adversos , Insuficiencia del TratamientoRESUMEN
Forty-two randomly selected patients were interviewed 2 to 14 years after termination of psychoanalytic group therapy. Comparison of psychodynamic changes in patients who stayed less than six months with those in patients who stayed more than two years gave a null result. The majority of patients were highly dissatisfied with their group experiences. However, there was a very strong positive correlation between favorable outcome and previous individual psychotherapy. Thirteen patients were then studied who were selected by their group therapists as having done well. These patients gave strong evidence of beneficial therapeutic effects, but such patients appear to be rare. These results (1) suggest how this form of treatment might be improved, and (2) raise questions about the appropriateness of transferring to group treatment the strictly psychoanalytic approach as used with individuals.
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Trastornos Neuróticos/terapia , Terapia Psicoanalítica , Psicoterapia de Grupo , Adulto , Actitud del Personal de Salud , Comportamiento del Consumidor , Empatía , Estudios de Evaluación como Asunto , Femenino , Estudios de Seguimiento , Procesos de Grupo , Humanos , Masculino , Relaciones Profesional-Paciente , Pronóstico , Psicoterapia , Factores de TiempoRESUMEN
This work is part of a study of 45 neurotic patients who were seen for consultation at the Tavistock Clinic but who never received treatment, and who, by the time they were asked to come for follow-up, had never been interviewed by a psychiatrist more than twice in their whole lives. In a previous report, we described 13 patients who were at least "improved" on purely symptomatic criteria but whom we did not regard as improved on dynamic criteria. Here, we describe 11 patients who were judged to be improved on dynamic criteria. These patients are of extraordinary interest, providing not only direct evidence of therapeutic mechanisms in everyday lifean answer to a question posed by Strupp and Bergin in 1969but also, quite unexpectedly, evidence about the therapeutic effects of single interviews.
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Trastornos Neuróticos , Adulto , Trastornos de Ansiedad/terapia , Depresión/terapia , Femenino , Estudios de Seguimiento , Humanos , Histeria/terapia , Entrevista Psicológica , Masculino , Trastornos Neuróticos/diagnóstico , Trastornos Neuróticos/terapia , Trastornos Parafílicos/terapia , Remisión Espontánea , Estrés PsicológicoRESUMEN
The synthetic growth hormone (GH) secretagogue hexarelin has important cardiac effects, that include a reduction of dysfunction in ischemic-reperfused hearts from GH-deficient rats after a chronic treatment and an increase of ejection fraction in acutely treated men. To investigate the mechanisms of its cardiac activity, we studied the effects of hexarelin (1-10 microM) on contractility of rat papillary muscles. We observed, in hexarelin treated papillary muscles, an improved recovery of contractility after anoxia. Hexarelin induced time- and frequency-dependent inotropic effects on papillary muscle. These effects were a transient increase in contractile force, abolished by propranolol (0.2 microM), followed by a reduction at low (60-240/min), but not at high (400-600/min) beating frequencies. The typical negative force-frequency relationship present in rat papillary muscles was therefore modified, and a minor increase in diastolic tension occurred after a sudden increase in stimulus frequency. Blockade of NO synthesis with 1 mM L-NAME, partially altered the response to hexarelin. MK-677 (1 microM), a non peptidyl GH secretagogue, reduced contractility, but did not alter the force-frequency relationship. The remaining effects of hexarelin were absent in papillary muscles pre-treated with indomethacin (1 microM), or after removal of endocardial endothelium with 0.5% triton X-100. The release of the prostacyclin metabolite 6-keto-PGF1alpha was increased during reoxygenation after a period of anoxia in hexarelin treated papillary muscles. Hexarelin had no significant effect on calcium transients and on I(Ca) measured in isolated ventricular cells. These findings suggest that the effects of hexarelin are mainly due to endothelium-released PGI2.
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Endotelio Vascular/fisiología , Contracción Miocárdica/fisiología , Oligopéptidos/farmacología , Función Ventricular , Animales , Relación Dosis-Respuesta a Droga , Contracción Miocárdica/efectos de los fármacos , Óxido Nítrico/fisiología , Ratas , Factores de TiempoRESUMEN
The linearity of the standard calibration curve in a flow-injection system involving a calcium-cresolphthalein complexone reaction was improved by replacing the organic base, 2-amino-2-methylpropan-1-ol, with the weak inorganic acid-conjugate base, boric acid-borate system as buffer. This was done after a theoretical study done on the relationship between the amount of coloured complex, Ca(2)(CPC)(2-), as major chromophore formed and the total amount of calcium added at different pH values, and employing the knowledge obtained via proton side-reactions. It was shown that a linear calibration curve between 150 and 1000 mg l(-1) of standard Ca(2-) solutions was obtained with a buffer solution containing 0.05 mol l(-1) boric acid, 0.05 mol l(-1) KCl and 35 g l(-1) sodium acetate at a pH of 8.5.
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Geraldton wax (Chamelaucium uncinatum, family Myrtaceae) plants are grown as cutflowers for the export market in South Africa. In July 1998, gall-like structures were observed on collars and roots of Geraldton wax plants in commercial fields in Wellington. The galls were observed after plants exhibited poor growth. The galls varied in size and in texture from soft and spongy to hard. Secondary symptoms involved poor root development and browning of stem tissues near galls. Isolations from the galls yielded nearly pure cultures of a Gram negative, rod-shaped bacterium on Roy Sauer medium (2), typical of an Agrobacterium sp. Carbon source utilization testing with the Biolog GN Bacterial Identification System (version 3.50) confirmed the bacterium as a biovar of A. tumefaciens with a similarity of 0.88. Pathogenicity was confirmed by injecting 4- to 6-week old tomato and tobacco plants and 1-year-old Geraldton wax plants with approximately 5 µl of the bacterial suspension (108 CFU/ml) in sterile, distilled water. Inoculated plants were then transferred to a greenhouse at 25°C. Galls developed 1 month after inoculation. The bacterium was readily reisolated from the inoculated plants. A. tumefaciens is endemic to South Africa and has a very wide host range that includes several ornamentals (1). This is the first report of A. tumefaciens on Geraldton wax plants in South Africa. References: (1) J. F. Bradbury. 1986. Guide to Plant Pathogenic Bacteria. CAB Int., Slough, U.K. (2) N. W. Schaad. 1988. Laboratory Guide for Identification of Plant Pathogenic Bacteria. The American Phytopathological Society, St. Paul, MN.
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The use of parallel computing in the finite element analysis of microwave heating applicators is discussed. Numerical results for a multiple feed cavity at 896 MHz and a cavity with a mode stirrer at 2.45 GHz are presented, and it is shown that for the two structures parallelism is most effectively introduced at different levels in the analysis.
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Simulación por Computador , Metodologías Computacionales , Calor , Microondas , Modelos Teóricos , Algoritmos , Estudios de Factibilidad , Análisis de Elementos FinitosRESUMEN
The Fischer-Tropsch (FT) process produces a variety of compounds over a wide carbon number range and the synthetic crude oil produced by this process is rich in highly valuable olefins and oxygenates, which crude oil only contains at trace levels. The characterization of these products is very challenging even when using comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC-TOF-MS). The separation between cyclic paraffins and olefins is especially difficult since they elute in similar positions on the GC×GC chromatogram and since they have identical molecular masses with indistinguishable fragmentation patterns. Previously, a high performance liquid chromatography (HPLC) fractionation procedure was used prior to GC×GC-TOF-MS analysis to distinguish between alkenes and alkanes, both cyclic and non-cyclic, however, there was co-elution of the solvents used in the HPLC fractionation procedure, and the volatile components in the gasoline sample and the dilution introduced by the off-line fractionation procedure made it very difficult to investigate components present at very low concentrations. The hyphenation of supercritical fluid chromatography (SFC) to GC×GC is less complicated and the removal of the supercritical CO2 can be easily achieved without any loss of the volatile sample components, eliminating the introduction of co-eluting solvents as well as the dilution effect. This paper describes the on-line hyphenation of SFC to a GC×GC system in order to comprehensively characterize the chemical groups (saturates, unsaturates, oxygenates and aromatics) in an FT sample.
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Alquenos/química , Cromatografía con Fluido Supercrítico/métodos , Cromatografía de Gases y Espectrometría de Masas/métodos , Parafina/química , Petróleo/análisis , Estructura MolecularAsunto(s)
Trastornos Mentales/terapia , Psicoterapia/historia , Investigación/historia , Adulto , Terapia Conductista , Estudios de Evaluación como Asunto , Estudios de Seguimiento , Historia del Siglo XX , Humanos , Trastornos Neuróticos/terapia , Trastornos de la Personalidad/terapia , Relaciones Médico-Paciente , Terapia Psicoanalítica , Trastornos Psicofisiológicos/terapia , Psicoterapia Breve , Psicoterapia de Grupo , Remisión Espontánea , Proyectos de Investigación , Transferencia Psicológica , Reino Unido , Estados UnidosRESUMEN
The aim of this study was to determine the effect of a worksite wellness programme on the physical work capacity profile of workers. Male workers who did not meet the minimum physical ability task requirement based on an assessment of ten essential physical abilities for their job were selected for this study. Twelve workers in the experimental group participated in a 24-month worksite wellness programme and 62 were in the control group. Pre- and post-tests determined if their physical work capacity profile met the minimum physical ability task requirements of their job. There was no practically significant (d = 0.8) difference between the two groups before the start of the programme after controlling for age; gender; motivation to change and initial physical work capacity profile differences. The results showed that workers whose physical work capacity profile did not meet the minimum physical ability task requirement of their job; were practically significantly (.......... = 4.25) more likely to improve their physical work capacity profile through the 24-month worksite wellness programme to a level were they met the minimum physical ability task requirement of the job; than those receiving no intervention. The study found that the cases were poorly reported. The follow up system at the local level between local government officials and the farmers was not efficient for the prevention of agrichemical poisonings. The contributory factors were insufficient information and training; the incorrect use of personal protective equipment; the lack of safety of the agri-chemical store; and the absence of a monitoring system on the majority of farms. This study demonstrated that the notification of agricultural chemical poisoning was applied in a fragmentary manner between the different governmental levels and departments
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Aptitud , Electricidad , Resistencia FísicaRESUMEN
BACKGROUND: Atazanavir (ATV), the first once-daily protease inhibitor approved for the treatment of HIV-1 infection, is recommended for use in antiretroviral (ARV) treatment-naive and -experienced patients. Study AI424-089 was a prospective, randomized, open-label, 96-week study comparing 2 ATV-based treatment regimens in ARV-naive HIV-infected patients. METHODS: Adults with HIV RNA levels > or =2000 copies/mL were randomized (1:1) to once-daily ATV at a dose of 300 mg with ritonavir at a dose of 100 mg (ATV300/RTV) or ATV at a dose of 400 mg (ATV400); both regimens included lamivudine and an investigational extended-release formulation of stavudine. The primary endpoint for this noninferiority study was the proportion of patients (response rate) with an HIV RNA load <400 copies/mL at week 48. RESULTS: Response rates at week 48 were 86% and 85% on the ATV300/RTV and ATV400 regimens, respectively (difference estimate [95% confidence interval] = 1.5 [-8.2 to 11.1]). There were 3 and 10 patients with virologic failure in the ATV300/RTV and ATV400 groups, respectively. One patient (ATV400) developed phenotypic resistance to ATV associated with an I50L substitution. Adverse event-related discontinuations were 8% among ATV300/RTV-treated patients and <1% among ATV400-treated patients. Plasma lipid elevations were low with both regimens. Both regimens were well tolerated. CONCLUSIONS: These findings demonstrate the safety and efficacy of the ATV300/RTV regimen and confirm the safety and efficacy of ATV400 in an ARV-naive patient population.
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Fármacos Anti-VIH/efectos adversos , Fármacos Anti-VIH/uso terapéutico , Terapia Antirretroviral Altamente Activa , Infecciones por VIH/tratamiento farmacológico , Oligopéptidos/efectos adversos , Oligopéptidos/uso terapéutico , Piridinas/efectos adversos , Piridinas/uso terapéutico , Ritonavir/uso terapéutico , Adulto , Anciano , Sustitución de Aminoácidos/genética , Fármacos Anti-VIH/administración & dosificación , Sulfato de Atazanavir , Farmacorresistencia Viral/genética , Femenino , VIH-1/efectos de los fármacos , Humanos , Lamivudine/uso terapéutico , Lípidos/sangre , Masculino , Pruebas de Sensibilidad Microbiana , Persona de Mediana Edad , Oligopéptidos/administración & dosificación , Estudios Prospectivos , Piridinas/administración & dosificación , ARN Viral/sangre , Ritonavir/administración & dosificación , Estavudina/uso terapéutico , Carga Viral , Privación de TratamientoRESUMEN
Meridional profiles of variation of dioptric power are constructed. Using the basic theory developed in an accompanying paper, samples are selected in a systematic way to illustrate variation only in sphere, only in cylinder and only in axis, and in all possible combinations of sphere, cylinder and axis. For each of the seven samples, scatter plots are constructed together with ellipsoids that represent the estimated distribution of powers in the population from which the sample was taken. The surfaces of the ellipsoids are surfaces of constant probability density within which 95% of the population is calculated to lie. The scatter plots and distribution ellipsoids are plotted in a three-dimensional space called h-space. Meridional profiles of variation are constructed for each of the samples. Properties of the profiles are discussed. Meridional profiles are also presented for eyes before and after radial keratotomy. Among other things, the profiles show meridians of greatest and least variation and are intuitively satisfying. They are potentially useful for the researcher and clinician including the surgeon. They may help to improve surgical and therapeutic techniques. Certain patterns may prove to be characteristic of physiological or pathological conditions, in which case meridional profiles may have use as a diagnostic tool.
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Matemática , Refracción Ocular , Análisis de Varianza , HumanosRESUMEN
Recently developed methods of quantifying changing dioptric power are applied to the refractive status of Hong Kong Chinese infants from about 10 to about 40 weeks of age. The analysis confirms that hyperopia decreases during the period and that with-the-rule astigmatism predominates. Change, however, is not constant over the period. The rate of decrease of hyperopia slows down and the refractive status becomes more spherical. The mean refractive status is calculated at 10, 20, 30 and 40 weeks. The spread of refractive status is represented by variance-covariance matrices calculated for each group and 95% confidence ellipsoids on the mean are constructed. The variance-covariance exhibits little change over the period. The right and left eyes show similar behaviour.
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Refracción Ocular , Envejecimiento/fisiología , China/etnología , Hong Kong , Humanos , Lactante , MatemáticaRESUMEN
Refractive status can be represented as a point plotted on a three-dimensional graph. As the refractive status changes a curve is traced out on the graph. Trajectories of changing refractive status are illustrated in a number of representative ideal cases. The three-dimensional graphs are shown by means of stereo-pairs. Trajectories are constructed from clinical data and interpreted with reference to the ideal examples. They show changing refractive status with age, after cataract extraction, and after radial keratotomy. The trajectories may prove to be a useful tool for both clinician and researcher. They show overall trends and allow prediction of future changes. Certain types of trajectories could prove to be characteristic of certain conditions and thus be useful for diagnosis. Trajectories allow monitoring of change after intervention.
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Envejecimiento/fisiología , Percepción de Movimiento , Errores de Refracción/fisiopatología , Adolescente , Adulto , Anciano , Extracción de Catarata , Niño , Humanos , Queratotomía Radial , Masculino , Persona de Mediana EdadRESUMEN
Confidence regions for mean dioptric power can be represented by ellipsoids in a three-dimensional space called h-space. A convenient graphical representation is provided by stereo-pair drawings that, at a glance, show the estimated accuracy with which the mean power is known. As an example, a sample of autorefractor measurements made on one eye were used to construct a 95% confidence ellipsoid for the mean objective refractive status of that eye. Key dimensions of the ellipsoid are compared with those of another eye. The analysis is of fundamental importance for scientific studies of variation and change of refractive status. Its potential clinical importance is also discussed.
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Intervalos de Confianza , Óptica y Fotónica , Errores de Refracción , Adulto , Humanos , MasculinoRESUMEN
A sample from a population of dioptric powers may be used to estimate the distribution of dioptric powers in the population itself. This paper describes the method and shows further how one can obtain a graphical representation of the distribution. The graphical representation takes the form of ellipsoids of constant probability density. The centroid of each ellipsoid estimates the mean of the population while the size, shape and orientation show the extent and nature of the spread of the population. For illustrative purposes the theory is applied to measurements of refractive status before and after radial keratotomy. The ellipsoids are presented as stereo-pairs. They are useful for comparative and predictive purposes. Thus the ellipsoid that contains 95% of the population after surgery defines the set of refractive errors within which the refractive error of a particular eye can be expected to fall with a probability of 95%.