Changes in glaucomatous optic disc cupping or variability of computerized topographic measurements?
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Glaucoma↗
Biomedical subjects
L Dandona
Publications and source records attributed to L Dandona.
Reliability of optic nerve head topographic measurements with computerized image analysis.
We evaluated the reliability of optic disk area and disk rim area measurements obtained with the Humphrey Retinal Analyzer from ten repeat fundus images each of one eye of ten normal subjects and ten subjects with increased intraocular pressure. Variability of rim and disk areas was not significantly different between these two groups (P greater than .05), nor was it significantly different between images acquired during the same session and those acquired during different sessions (P greater than .05). Variability was significantly different between subject groups based on the distinctness of the disk edge and the slope of the cup wall (P less than .01). The average minimum change in the measurements on the same eye that would exceed variability of the technique at the 95% confidence level was 0.20 mm2 and 0.47 mm2 for rim area for the least variable and most variable subject groups based on optic nerve head characteristics, and 0.09 mm2 and 0.32 mm2 for disk area for the corresponding subject groups. Operator input contributed significantly to overall variability. Reliability of rim and disk areas in this study was comparable to that reported for other computerized image analyzers.
Adult↗
Variability of depth measurements of the optic nerve head and peripapillary retina with computerized image analysis.
Computerized topographic mapping of 10 repeated fundus images of one eye each in 10 healthy subjects and in 10 subjects with elevated intraocular pressures (IOPs) was performed with the Humphrey Retinal Analyzer. The variability of depth measurements at 400 to 650 individual locations in the optic nerve head and peripapillary retina was evaluated. The average size of the 95% confidence intervals for individual depth measurements for healthy subjects and those with elevated IOPs were 166 and 232 microns in the optic nerve head and 205 and 261 microns in the peripapillary retina, respectively. Variability was significantly less for healthy subjects than for those with elevated IOPs. Variability was significantly greater for depth measurements in the peripapillary retina than for measurements in the optic head. Knowledge about variability of individual depth measurements is useful for proper interpretation of computerized topographic mapping to detect retinal nerve fiber damage.
Adult↗
"Outlier" intraocular pressure readings: valid or invalid for statistical analysis?
Wide variations in the response to intraocular (IOP)-lowering medications may be due to the normal response of the subjects or to variables unrelated to the effect of medication, eg, noncompliance or recording errors. We used data from a previous study of medications designed to lower IOP to investigate the influence of readings showing an unusually large increase in IOP from baseline on the statistical analysis and conclusions. These readings, which could have been due to variables unrelated to the effect of medication, were defined as "outliers" by a statistical method. A statistically insignificant difference between two IOP-lowering medications became significant on excluding two subjects with outlier IOP readings. We explain how reporting results obtained with and without including outliers in the analysis may provide clinicians with more complete information.
Analysis of Variance↗
Awareness of eye donation in an urban population in India.
PURPOSE: Awareness of eye donation and willingness to pledge eyes for donation was assessed in the urban population of Hyderabad, India, where corneal blindness is a significant problem. METHODS: A total of 2522 subjects of all ages, representative of the Hyderabad population, participated in the Andhra Pradesh Eye Disease Study. Subjects >15 years old were interviewed regarding awareness of eye donation and willingness to pledge eyes for donation. RESULTS: Age-gender-adjusted prevalence of awareness of eye donation was 73.8% (95% CI: 66.5-81.0%) but only 1.9% (95% CI: 0.16-3.66%) had pledged eyes. With multivariate analysis, significantly less awareness of eye donation was found in illiterate subjects (OR 0.1; 95% CI: 0.1-0.14), subjects > or =70 years old (OR 0.3; 95% CI: 0.2-0.6), subjects of lower socio-economic status (OR 0.4; 95% CI: 0.3-0.6), females (OR 0.6; 95% CI: 0.5-0.8) and Muslims (OR 0.7; 95% CI: 0.6-0.9). Media was the major source of information about eye donation. Of those aware of eye donation, 44.9% were willing to pledge eyes. Willingness to pledge eyes for donation was significantly lower in Muslims (OR 0.18; 95% CI: 0.13-0.24) than in Hindus and in subjects > or =60years old (OR 0.3; 95% CI: 0.2-0.5). CONCLUSIONS: These data show that although only a few had pledged eyes there is enough potential in this population for obtaining many more corneas for transplantation. The information about distribution and demographic associations of awareness and willingness for eye donation could help in developing strategies to increase procurement of corneas for dealing with corneal blindness.
Adolescent↗
Estimation of blindness in India from 2000 through 2020: implications for the blindness control policy.
BACKGROUND: To eliminate avoidable blindness in India, appropriate national planning is necessary, which should be based on current and reliable data. A national survey done in 1986-89 reported that 1.5% of the Indian population (12 million people) was blind with a presenting visual acuity of < 6/60 in the better eye. The original goal of the National Programme for Control of Blindness was to reduce this prevalence to 0.3% by 2000. We have recently reported the prevalence of blindness in the population of Andhra Pradesh to be 1.66% with a presenting visual acuity of < 6/60 in the better eye as the sole criterion and 1.84% with a presenting visual acuity of < 6/60 orcentral visual field < 20 degrees in the better eye. We used these population-based data to estimate blindness in India in 2000 and project the possible scenarios of blindness through 2020 with different emphases of the blindness control policy in India. METHODS: Recent population-based data on the age-, sex- and cause-specific blindness rates from the Andhra Pradesh Eye Disease Study for the entire age range were applied to the population distribution of India to estimate the number of blind persons in 2000. The age-, sex- and cause-specific rates of blindness were then applied to the estimated age, sex and urban-rural population distribution of India in 2010 and 2020 to project the number of persons blind (from various causes) and the blind person-years that would be suffered under varying degrees of emphasis in the policy to control blindness due to particular diseases. For these projections, blindness was defined as a presenting distance visual acuity of < 6/60 or central visual field < 200 in the better eye. RESULTS: The number of blind persons in India in 2000 was estimated to be 18.7 million (95% confidence interval [CI]: 15.2-22.3), of which 9.5 million were cataract-related and 3 million refractive error-related. If there is no change in the current trend of blindness, the number of blind persons in India would increase to 24.1 million (95% CI: 19.7-28.4) in 2010, and to 31.6 million (95% Cl: 26.4-36.9) in 2020. If effective strategies are put in place to eliminate 95% of blindness due to cataract by 2020, blindness in 15.6 million persons would be prevented who would otherwise be blind in 2020 if the current trend continues, and 78 million blind person-years would be prevented in these persons. Similarly, if effective strategies are also implemented to eliminate 95% of the refractive error blindness by 2020, another 4.2 million persons would be prevented from being blind in 2020, and 82 million blind person-years would be prevented. In addition, if strategies to prevent 90% of the preventable blindness due to corneal disease and glaucoma are successful by 2020, blindness in an additional 3.6 million persons in 2020 and 29 million blind person-years would be prevented. CONCLUSION: The planning of blindness control in India should take into account recent population-based data for the entire age range, which suggest that the number of blind persons in India is currently over 18 million. This estimate is 50% more than the figure of 12 million from a decade ago that is still quoted widely in the blindness control policy documents. If avoidable blindness is to be substantially reduced in India by 2020, effective strategies against blindness due to cataract and refractive error are needed urgently as both these conditions are relatively easy to treat. Also, strategies against preventable corneal and glaucoma blindness need to be strengthened soon for them to show an impact over the next two decades.
Adolescent↗
Cost and efficiency of HIV voluntary counselling and testing centres in Andhra Pradesh, India.
BACKGROUND: [corrected] As part of the effort to control HIV/AIDS, the number of HlV voluntarycounselling and testingcentres (VCTCs) is increasing rapidly in the public health system of the Indian state of Andhra Pradesh, which is estimated to have one of the highest rates of HIV infection in India. However, systematic data on the cost and efficiency of providing VCT services in India are not available to help guide efficient use of resources for these services. METHODS: We used standardized methods to obtain detailed cost and output data for the 2002-03 fiscal year from written records and interviews in 17 VCTCs in the public health system in Andhra Pradesh. We calculated the economic cost per client receiving VCT services, and analysed the variation and determinants of total and unit costs across VCTCs. We used multivariate regression techniques to estimate incremental unit costs. We assessed hurdles towards serving an optimal number of clients by VCTCs. RESULTS: In the 2002-03 fiscal year, 32 413 clients received the complete sequence of services at the 17 VCTCs, including post-HIV test counselling. The number of clients served by each VCTC ranged from 334 to 7802 (median 979). The overall HIV-positive rate in post-test counselled clients was 20.5% (range 5.4%-52.6%). The cost per client for the complete VCT sequence varied 6-fold between VCTCs (range Rs 141.5-829.6 [US 2.92-17.14 dollars], median Rs 363.5 [US 7.51 dollars]). The cost per client was significantly lower at VCTCs with more clients (p < 0.001, R2 = 0.83; power function) due to substantial fixed costs. Personnel made up the largest component of cost (53.7%). The cost per client had a significant direct relation with percent personnel cost for VCTCs (p < 0.001, R2 = 0.58; exponential function). A multiple regression model revealed that the incremental cost of providing complete VCT services to each HIV-positive and -negative client was Rs 123.5 (US 2.54 dollars) and Rs 59.2 (US 1.22 dollars), respectively. Fourteen VCTCs (82.4%) reported that they could serve more clients with the available personnel and infrastructure, and that inadequate demand for their services was the main hurdle towards achieving this. CONCLUSION: These data suggest that the efforts of the National AIDS Control Organisation of India and the Andhra Pradesh State AIDS Control Society in increasing VCTCs could yield even higher benefit if the demand for these services was enhanced, as this would increase the number of clients served and reduce the cost per client. Ongoing systematic cost-efficiency analysis is necessary to help guide efficient use of HIV-control resources in India.
AIDS Serodiagnosis↗