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Biomedical subjects

P J Foster

Publications and source records attributed to P J Foster.

48 records · Page 3Linked to original sources
PubMed1998

Measurement of optic disc size: equivalence of methods to correct for ocular magnification.

AIMS: To compare methods available to correct the magnification of images that result from the optics of the eye and identify errors, and source of error, of the methods. METHODS: 11 methods were applied to ocular biometry data from three independent cohorts. Each method was compared with the method of Bennett, which uses most biometric data. The difference between each method and Bennett's is the "error" of the method. The relation between the error and axial length, ametropia, and keratometry was explored by linear regression analysis. RESULTS: Methods using axial length had the lowest mean (+0.5 to +2.6%) and standard deviation (0.6 to 1.2%) of errors. Of methods using keratometry and ametropia only, the lowest mean (-1.4% to +4.4%) and standard deviation (2.9 to 4.3%) of errors was found for a new method described in this paper, and that used by the Heidelberg retina tomograph (HRT). The highest mean error (+2.2 to +7.1%) was found for Littmann's method. Littmann's correction was larger than the HRT's by 3.5 to 3.7%. The mean difference between the new and HRT methods and the "abbreviated axial length" method of Bennett is -1.3 to +2.0%. The error of the "keratometry and ametropia" methods is related to axial length. CONCLUSIONS: Methods using axial length are most accurate. The abbreviated axial length method of Bennett differs little from more detailed calculations and is appreciably more accurate than methods using keratometry and ametropia alone. If axial length is unknown, the new and the HRT methods give results closest to the abbreviated axial length method.

Aged↗
PubMed1998

The relationship between stature, growth, and short-term changes in height and weight in normal prepubertal children.

Human growth is a nonlinear process with marked variation in growth rate during the short-term. It is not known how long-term height gain or stature is influenced by short-term changes in height and weight. This study has addressed these issues by using thrice weekly height and weight measurements during 1 year in 43 normal prepubertal children (aged 5.7-7.7 y) to construct individual height and weight velocity curves by regression analysis. The former were comprised of 3 to 6 growth spurts separated by stasis, whereas the latter were characterized by 2 to 5 periods of weight gain separated by periods of weight loss. Stepwise regression analysis to determine characteristics of these curves that influence stature and growth showed that height SD score was correlated to the mean absolute weight velocity amplitude (+), the mean length of height velocity peaks (-), and the number of periods of weight gain (-) (r2 = 38%). In contrast, change in height SD score (delta height SD score) was correlated to the number (+) and mean amplitude (+) of the periods of weight gain and the mean height velocity peak amplitude (+) (r2 = 44%). Examination of changes in height relative to weight during the year in the whole group revealed that height increased relative to weight in autumn and spring, whereas the reverse occurred during the winter months. We conclude that 1) both height and weight velocities during 1 year show a biphasic pattern, 2) there is seasonal variation in the short-term change in height relative to weight, and 3) prepubertal stature and the amount grown through the year are related to short-term changes in height and weight. Our data indicate that large but infrequent changes in weight with growth spurts of short duration are found in tall children. Good growth during the year was related to large but frequent gains in weight and large individual spurts in height.

Body Height↗
PubMed1997

Incidence of acute primary angle-closure glaucoma in Singapore. An island-wide survey.

OBJECTIVES: To determine the incidence of acute primary angle-closure glaucoma (APACG) in Singapore and to identify demographic and meteorological risk factors. DESIGN: A prospective, island-wide incidence study. SETTING: All government and private ophthalmological practices in Singapore, from March 1, 1995, to February 29, 1996. METHODS: New cases of APACG were identified by all ophthalmologists in Singapore during a 1-year period. Demographic and clinical details were recorded. RESULTS: One hundred eighty-nine people (208 eyes) were seen with APACG for the first time during the 1-year period. These new cases represent an incidence of 12.2 per 100,000 per year (95% confidence interval, 10.5-13.9) in those aged 30 years and older. Major risk factors identified were female sex (relative risk, 2.4), Chinese ethnic origin (relative risk, 2.8), and age of 60 years or older (relative risk, 9.1). Half of those affected were seen 3 days or more after the onset of symptoms. Attacks were more frequent on hotter days. There also was a relationship between the number of attacks per day and the mean number of sunspots and mean solar radio flux during the previous 30 days. CONCLUSIONS: There is a high incidence of APACG in Singapore, with elderly women being the highest risk group. Chinese Singaporeans are at higher risk than other ethnic groups (Malay and Indian). There is often a substantial delay before these patients consult a physician. The onset of APACG seems to be associated with meteorological factors.

Acute Disease↗
PubMed1997

Anterior chamber depth in Mongolians: variation with age, sex, and method of measurement.

PURPOSE: To document anterior chamber depth in a Mongolian population and quantify the variation in this parameter attributable to age, sex, and method of measurement. METHOD: Depth of the anterior chamber was measured by optical pachymetry in 1,242 subjects aged 10 to 87 years. Figures for "true" anterior chamber depth were calculated by subtracting central corneal thickness from the distance between the anterior corneal epithelium and anterior lens capsule. A-mode ultrasound was also used to measure the distance from anterior corneal epithelium to anterior lens capsule in 94% (942) of subjects aged 40 years and older. These ultrasound data were compared with measurements of the same distance obtained by optical pachymetry. RESULTS: Mean anterior chamber depth in women was more shallow than in men of all ages (ANOVA, P < .0001), although this difference varied according to age. Mean anterior chamber depth decreased with age and was most accurately represented by a cubic function of age. This change was maximal between the ages of 30 and 60 years and equaled 0.15 mm per decade in men and 0.21 mm per decade in women. Mean depth of the anterior chamber measured by ultrasound was significantly less than the equivalent optical measurement (difference of 0.14 mm in right eyes, P < .001). CONCLUSIONS: Mean anterior chamber depth in Mongolians decreases with age and is more shallow in women than in men. Ultrasound and optical methods of anterior chamber depth measurement yield significantly different results and are therefore not directly comparable.

Adolescent↗
PubMed1996

Glaucoma in Mongolia. A population-based survey in Hövsgöl province, northern Mongolia.

OBJECTIVES: To determine the prevalence of glaucoma and suspect glaucoma, and to classify the cases detected according to mechanism. DESIGN: A population-based prevalence study. SETTING: Rural and urban locations in Hövsgöl province, northern Mongolia. PARTICIPANTS: Nine hundred forty-two (94.2%) of 1000 individuals 40 years of age and older were examined. MAIN OUTCOME MEASURE: Primary angle-closure glaucoma was diagnosed in subjects with previous acute or intermittent symptoms of angle closure and in individuals with an occludable angle and an intraocular pressure greater than 19 mm Hg or a glaucomatous visual field. RESULTS: The prevalence of manifest primary angle-closure glaucoma was 1.4% (14 subjects). The prevalence of gonioscopically occludable angles was 6.4% (64 subjects, including those with glaucoma). Primary open-angle glaucoma was diagnosed in 5 subjects (prevalence, 0.5%). As all these subjects were older than 60 years, the prevalence became 2.1% for this age group. Three cases (prevalence, 0.3%) of secondary open-angle glaucoma were detected. No cases of secondary angle-closure glaucoma were diagnosed. The prevalence of blindness was 1.2% (12 subjects), and primary glaucoma accounted for one third of these cases (4 subjects). CONCLUSIONS: We confirmed glaucoma as a major public health problem in northern Mongolia. Primary angle-closure glaucoma is more prevalent than primary open-angle glaucoma, supporting clinic-based data from other east Asian countries. Among the subjects examined, 97 (9.7%) had either manifest, latent, or suspect glaucoma. Neighboring populations may be similarly affected owing to a shared genetic heritage.

Adult↗
PubMed1996

Model of normal prepubertal growth.

Growth over the short term is a highly complex non-linear process. Contrasting models of short term growth have been proposed which include periodic growth cycles versus abrupt growth spurts with intervening growth arrest ('saltation and stasis'). The variability of short term growth has been characterised from a study of 46 healthy prepubertal children measured three times a week over one academic year using a combination of descriptive statistical approaches and regression modelling. Growth in childhood over one year is represented by a biphasic process comprising three to six unpredictable growth spurts, each of mean length 56 days (range 13-155 days), separated by periods of stasis (less than or equal to 0.05 cm height increment over more than seven days), each lasting a mean of 18 days (range 8-52 days) and accounting for at least 20% of the period of observation. This is superimposed on strong seasonal trends in growth with a declining growth rate over the autumn months reaching a nadir in midwinter, followed by a growth spurt in the spring. Human growth over short periods is therefore a discontinuous, irregular, and unpredictable process.

Anthropometry↗
PubMed1995

Cataract surgery by junior ophthalmologists.

The first 50 cases of cataract extraction and lens implant operations performed by seven junior ophthalmologists were retrospectively reviewed to determine whether the surgical outcome of cataract surgery compares with the results of the National Cataract Surgery Survey. Main outcome measures were final visual acuity achieved and the incidences of surgically related complications. In all, 322 case notes were reviewed and full datasets were obtainable in 307 patients (95%). Overall 97% achieved a final visual acuity of 6/12 or better. Twenty per cent had coexisting ocular pathology, 7% had intraoperative complications and 21% had post-operative complications. The visual outcome compared acceptably with the results of the National Cataract Surgery Survey in Britain. The overall incidences of surgically related complications were also acceptable but the rate of vitreous loss was higher and post-operative complications tended to be of greater magnitude.

Cataract Extraction↗
PubMed1991

Assessing student outcomes in a nursing learning assistance program.

This study measured the apparent effectiveness of a Learning Assistance Program (LAP) in second-year baccalaureate nursing students using a process-outcome design. Seventy-eight students participated in LAP and 98 did not. SAT/ACT scores and freshman GPA were the cognitive "input" variables and the end-of-sophomore-year GPA the cognitive "outcome" variable. Affective variables at the beginning and end of the test year were the Study Attitudes and Methods Survey (SAMS) and the Survey of Reading and Study Efficiency (SR/SE). Statistical analysis included stepwise multiple regressions for evaluating the relationship between the process (LAP participation) and outcomes when the entry variables had been accounted for. Attending LAP improved participants' study attitudes and skills scores. There was a significant negative correlation between the degree of LAP participation by lower achieving students and their sophomore-year-ending GPA. This may be related to the fact that students who perform poorly on tests are encouraged to participate in LAP.

Adolescent↗
PubMed1981

Clinical discussion groups: verbal participation and outcomes.

The author studied both the amount and cognitive level of teacher questions and student discussion in 62 small clinical discussion groups comprising 119 third-year medical students. After analyzing the transcripts from over 75 hours in small clinical discussion groups, the investigator examined in detail how much the "process" of the small group interaction related to certain outcomes, such as the students' critical thinking and their performance on the examinations of the National Board of Medical Examiners. The instrument used for analysis was a modified version of the Flanders System of Interaction Analysis that incorporated Bloom's Taxonomy of the Cognitive Domain. The cognitive level of the teachers' questions had a significant positive correlation with the cognitive level of the students' responses. While there were significant relationships between some aspects of verbal participation and outcome measures, the multiple regression analyses showed that the major contributions to outcomes were the aptitude and previous knowledge that the students already possessed.

Cognition↗
PubMed1979

Verbal participation and outcomes in medical education. A study of third-year clinical discussion groups.

This study looked at several aspects of clinical instruction in small groups such as teacher questioning and student discussion and documented how certain student cognitive outcomes are related to them. Drawing from actual transcripts of over 75 hours in small group sessions, the study examined in detail such things as the logic and level of the questions medical teachers ask, the quality of student responses, the cognitive level of classroom discourse and the effects of instruction on selected outcomes such as the students' ability to think critically and their performance on National Board of Medical Examiners examinations. The instrument used for teaching analysis was a modified version of the Flanders System of Interaction Analysis which incorporated Bloom's Taxonomy of the Cognitive Domain. The cognitive level of the teachers' questions had a significant relationship to the cognitive level of the students' response and discussion. While the students who talked at the highest cognitive level in class were those who scored highest in National Board Examinations (Parts 1 and 2) and the critical thinking tests, the multiple regression analyses showed that classroom activity contributed little to outcomes. The major contributions to outcomes were the aptitude and previous knowledge that the students already possessed.

California↗
PubMedDate not supplied

Short-term growth in children with growth disorders.

OBJECTIVE: We have previously demonstrated that normal prepubertal growth over 1 year is composed of growth spurts lasting an average of 8 weeks, separated by periods of very slow growth or stasis. We have now analysed short-term growth patterns in eight children with different growth disorders: Turner syndrome (n = 2), intrauterine growth retardation (IUGR, n = 1) and growth hormone (GH) deficiency (GHD, n = 5). METHODOLGY: Height was measured daily in the morning by parents over 4-12 months. Regression and time series analysis were used to characterize short-term growth. In two boys (GHD and IUGR) their normal twin brother was measured in parallel. RESULTS: All height velocity curves, based on regression analysis, showed a biphasic pattern, characterized by growth spurts of varying amplitudes and periods of very slow growth or growth stasis. When compared to growth curves in normal children, the principal qualitative differences in GHD and Turner syndrome were increased stasis time and reduced growth spurt amplitude. In IUGR reduced amplitude and length of growth spurts were seen, but the time spent in stasis was similar to normal children. Two naive patients with GHD increased the amplitude of their growth spurts by a mean 0.013 cm day(-1) on GH treatment, with the mean length of their growth spurts increasing by 10 days. Their time spent in stasis decreased from 19% to 6% on GH. In two subjects with GHD the growth pattern during maintenance GH treatment was similar to that seen in normal children. Using time series analysis significant periodicities in height measurements were seen in the majority of children with growth disorders, which disappeared in patients with GHD in the catch-up phase after commencing GH therapy. CONCLUSIONS: (1) The growth spurts and stases seen in normal children are also observed in those with growth disorders, (2) different growth disorders have variable effects on the spurt stasis model of childhood growth, (3) catch-up growth on GH in children with GHD was achieved by increasing the amplitude of the growth spurts and reducing the time spent in stasis.

Body Height↗