Relationship between visual field loss and contrast threshold elevation in glaucoma

BACKGROUND: There is a considerable body of literature which indicates that contrast thresholds for the detection of sinusoidal grating patterns are abnormally high in glaucoma, though just how these elevations are related to the location of visual field loss remains unknown. Our aim, therefore, has been to determine the relationship between contrast threshold elevation and visual field loss in corresponding regions of the peripheral visual field in glaucoma patients. METHODS: Contrast thresholds were measured in arcuate regions of the superior, inferior, nasal and temporal visual field in response to laser interference fringes presented in the Maxwellian view. The display consisted of vertical green stationary laser interference fringes of spatial frequency 1.0 c deg(-1 )which appeared in a rotatable viewing area in the form of a truncated quadrant extending from 10 to 20° from fixation which was marked with a central fixation light. Results were obtained from 36 normal control subjects in order to provide a normal reference for 21 glaucoma patients and 5 OHT (ocular hypertensive) patients for whom full clinical data, including Friedmann visual fields, had been obtained. RESULTS: Abnormally high contrast thresholds were identified in 20 out of 21 glaucoma patients and in 2 out of 5 OHT patients when compared with the 95% upper prediction limit for normal values from one eye of the 36 normal age-matched control subjects. Additionally, inter-ocular differences in contrast threshold were also abnormally high in 18 out of 20 glaucoma patients who had vision in both eyes compared with the 95% upper prediction limit. Correspondence between abnormally high contrast thresholds and visual field loss in the truncated quadrants was significant in 5 patients, borderline in 4 patients and absent in 9 patients. CONCLUSION: While the glaucoma patients tested in our study invariably had abnormally high contrast thresholds in one or more of the truncated quadrants in at least one eye, reasonable correspondence with the location of the visual field loss only occurred in half the patients studied. Hence, while contrast threshold elevations are indicative of glaucomatous damage to vision, they are providing a different assessment of visual function from conventional visual field tests

Earthworms and in vitro physiologically-based extraction tests : complementary tools for a holistic approach towards understanding risk at arsenic-contaminated sites

The relationship of the total arsenic content of a soil and its bioaccumulation by earthworms (Lumbricus rubellus and Dendrodrilus rubidus) to the arsenic fraction bioaccessible to humans, measured using an in vitro physiologically-based extraction test (PBET), was investigated. Soil and earthworm samples were collected at 24 sites at the former arsenic mine at the Devon Great Consols (DGC) in southwest England (UK), along with an uncontaminated site in Nottingham, UK, for comparison. Analysis of soil and earthworm total arsenic via inductively coupled plasma mass spectrometry (ICP-MS) was performed following a mixed acid digestion. Arsenic concentrations in the soil were elevated (204–9,025 mg kg−1) at DGC. The arsenic bioaccumulation factor (BAF) for both earthworm species was found to correlate positively with the human bioaccessible fraction (HBF), although the correlation was only significant (P ≤ 0.05) for L. rubellus. The potential use of both in vitro PBETs and earthworms as complementary tools is explored as a holistic and multidisciplinary approach towards understanding risk at contaminated sites. Arsenic resistant earthworm species such as the L. rubellus populations at DGC are presented as a valuable tool for understanding risk at highly contaminated sites

Cost of hemodialysis in a public sector tertiary hospital of India

Introduction Nearly 220 thousand patients are diagnosed with End Stage Renal Disease (ESRD) 33 every year, which calls for an additional demand for 34 million dialysis sessions in India. The Government of India has announced a National Dialysis Program to provide for free dialysis in public hospitals. In this paper, we estimate the overall cost of performing hemodialysis (HD) in a tertiary care hospital. Secondly, we also assess the catastrophic impact of out of pocket expenditure for hemodialysis on households and its determinants. Methods Economic health system cost of HD was estimated using bottom-up costing methods. All resources, capital and recurrent, utilized for service delivery from April 2015 to March 2016 were identified, measured and valued. Capital costs were annualized after accounting for their useful life and discounting at 3% for future years. Sensitivity analyses were undertaken to determine the effect of variation in the input prices, and other assumptions on the annual health system cost. Out of pocket expenditure (OOPE) was assessed by interviewing 108 patients undergoing HD in the study hospital to account for cost from the patient’s perspective. The prevalence of catastrophic health expenditure (CHE) was computed as per threshold of 40% of non-food expenditure. Results The overall average cost incurred by the health system per HD session was INR 4,148 (USD 64). Adjusting for capacity utilization, health system incurred INR 3,025 (USD 47) per hemodialysis at 100% bed-occupancy. The mean out of pocket expenditure per patient per session was INR 2,838 (USD 44;95% CI: USD 34-55). Major component of this OOPE was on medicines and consumables (64.1%). The prevalence of catastrophic health expenditure per HD session was 11.1%. Conclusion Our study findings would be useful in context of planning for dialysis services, set provider payment rates for dialysis under various publicly sponsored health insurance schemes, and undertake future cost-effectiveness analysis to guide resource allocation decisions.</p