Linking structure and function in glaucoma.

The glaucomas are a group of relatively common optic neuropathies, in which the pathological loss of retinal ganglion cells causes a progressive loss of sight and associated alterations in the retinal nerve fiber layer and optic nerve head. The diagnosis and management of glaucoma are often dependent on methods of clinical testing that either, 1) identify and quantify patterns of functional visual abnormality, or 2) quantify structural abnormality in the retinal nerve fiber layer, both of which are caused by loss of retinal ganglion cells. Although it is evident that the abnormalities in structure and function should be correlated, propositions to link losses in structure and function in glaucoma have been formulated only recently. The present report describes an attempt to build a model of these linking propositions using data from investigations of the relationships between losses of visual sensitivity and thinning of retinal nerve fiber layer over progressive stages of glaucoma severity. A foundation for the model was laid through the pointwise relationships between visual sensitivities (behavioral perimetry in monkeys with experimental glaucoma) and histological analyses of retinal ganglion cell densities in corresponding retinal locations. The subsequent blocks of the model were constructed from clinical studies of aging in normal human subjects and of clinical glaucoma in patients to provide a direct comparison of the results from standard clinical perimetry and optical coherence tomography. The final formulation is a nonlinear structure-function model that was evaluated by the accuracy and precision of translating visual sensitivities in a region of the visual field to produce a predicted thickness of the retinal nerve fiber layer in the peripapillary sector that corresponded to the region of reduced visual sensitivity. The model was tested on two independent patient populations, with results that confirmed the predictive relationship between the retinal nerve fiber layer thickness and visual sensitivities from clinical perimetry. Thus, the proposed model for linking structure and function in glaucoma has provided information that is important in understanding the results of standard clinical testing and the neuronal losses caused by glaucoma, which may have clinical application for inter-test comparisons of the stage of disease.

Comparison of direct health care costs related to the pharmacological treatment of osteoporosis and to the management of osteoporotic fractures among compliant and noncompliant users of alendronate and risedronate: a population-based study.

UNLABELLED: This population-based study aimed to compare direct health care costs related to the pharmacological treatment of osteoporosis and to the management of osteoporotic fractures among compliant and noncompliant users of alendronate and risedronate. During a 2-year follow-up period, compared to those with medication possession ratio (MPR) > or = 80%, women with MPR < 80% incurred significantly higher physician care costs and hospital care costs. INTRODUCTION: This study aimed to compare direct health care costs related to the treatment of osteoporosis and osteoporotic fractures among compliant and noncompliant users of alendronate and risedronate. METHODS: A cohort of 15,027 women having initiated alendronate or risedronate was identified. MPR and direct health care costs (physician care, hospital care, drugs) were assessed during a 2-year period. Regression models were used to estimate mean predicted cost for compliant (MPR > or = 80%) and noncompliant (MPR < 80%) women. RESULTS: Mean predicted physician care cost (in Canadian dollars) was $51 among women with MPR < 80% and $34 among those with MPR > or = 80%: mean difference $17, 95% confidence interval (CI) $2-22. Mean predicted hospital care cost was $568 among women with MPR < 80% and $379 among those with MPR > or = 80%: mean difference $189, 95% CI $56-320. Mean predicted drug cost was $439 among women with MPR < 80% and $1,068 among those with MPR > or = 80%: mean difference $-639, 95% CI $-649 to -629. CONCLUSION: Compared to compliant women, noncompliant women incurred significantly higher physician care and hospital care costs. Due to lower drug costs, total direct health care costs were lower among noncompliant women.

Cellulitis in broiler chickens: a one-year retrospective study in four Québec abattoirs.

A 1-yr retrospective study was undertaken to verify whether the prevalence of cellulitis in broiler chicken flocks was associated 1) with sex and average body weight controlling for the time of year and 2) with some other condemnation causes such as air-sacculitis, ascites, cyanosis, emaciation, valgus varus deformity, peritonitis, and total condemnation rate controlling for sex, average body weight, and time of year. Data were collected from four Québec abattoirs between October 1992 and September 1993. Data from 2452 unisex male and female broiler flocks were compiled and analyzed with univariate and multivariate models. The prevalence of cellulitis among flocks was 42.2 per 10,000 birds slaughtered. Cellulitis was associated with sex and increased with time of year (P < 0.0001). The prevalence was higher in male (mean +/- SD, 50.7+/-24.3; median, 31.8) than in female flocks (mean +/- SD, 34.2+/-15.6; median, 20.0) but showed no relationship with average body weight. Associations between condemnation causes and cellulitis were relatively weak; increases in the prevalence of cellulitis correlated with increases in total condemnation rate (r2 = 0.19), ascites (r2 = 0.09), airsacculitis (r2 = 0.0), cyanosis (r2 = 0.04), peritonitis (r2 = 0.03), emaciation (r2 = 0.02), and valgus varus deformity (r2 = 0.02). These results suggest that flock sex is a potential correlate of cellulitis prevalence in broiler chickens. Associations between the prevalence of cellulitis and other diseases observed at the abattoir were not very strong. However, it appears here that general disease status of Québec broiler flocks is a better indicator of cellulitis occurrence than the main diseases considered individually.