Biomedical subjects

Hans Limburg

Publications and source records attributed to Hans Limburg.

5 recordsLinked to original sources

PubMed2004

Field trial of applicability of lot quality assurance sampling survey method for rapid assessment of prevalence of active trachoma.

OBJECTIVE: To test the applicability of lot quality assurance sampling (LQAS) for the rapid assessment of the prevalence of active trachoma. METHODS: Prevalence of active trachoma in six communities was found by examining all children aged 2-5 years. Trial surveys were conducted in these communities. A sampling plan appropriate for classifying communities with prevalences < or =20% and > or =40% was applied to the survey data. Operating characteristic and average sample number curves were plotted, and screening test indices were calculated. The ability of LQAS to provide a three-class classification system was investigated. FINDINGS: Ninety-six trial surveys were conducted. All communities with prevalences < or =20% and > or =40% were identified correctly. The method discriminated between communities with prevalences < or =30% and >30%, with sensitivity of 98% (95% confidence interval (CI)=88.2-99.9%), specificity of 84.4% (CI=69.9-93.0%), positive predictive value of 87.7% (CI=75.7-94.5%), negative predictive value of 97.4% (CI=84.9-99.9%), and accuracy of 91.7% (CI=83.8-96.1%). Agreement between the three prevalence classes and survey classifications was 84.4% (CI=75.2-90.7%). The time needed to complete the surveys was consistent with the need to complete a survey in one day. CONCLUSION: Lot quality assurance sampling provides a method of classifying communities according to the prevalence of active trachoma. It merits serious consideration as a replacement for the assessment of the prevalence of active trachoma with the currently used trachoma rapid assessment method. It may be extended to provide a multi-class classification method.

Confidence Intervals↗

PubMed2003

Cataract blindness in Chakwal District, Pakistan: results of a survey.

AIM: To present the results of a rapid assessment of cataract surgical services in Chakwal District, Pakistan. METHODS: 40 clusters of 40 persons of 50 years and older (1600 eligible persons) were selected by systematic random sampling from the entire Chakwal district. A total of 1505 persons were examined (coverage 94%). RESULTS: Cataract is the major cause of bilateral blindness (46.5%). The age and sex adjusted prevalence of bilateral cataract blindness (VA < 3/60) in people of 50 years and older was 2.0% (95% CI: 1.2-3.2%), with a cataract surgical coverage of 92% for males and 73% for females, a significant difference. The prevalence of bilateral cataract and VA < 6/60 in persons of 50 years and older was 5.1% (95% CI: 3.6-6.9), an estimated total of 8833 persons. In this last group, the surgical coverage was 66% (persons) and 50% (eyes). Of the patients operated with IOL implantation, 12% could not see 6/60, while 36% of those operated without IOL could not see 6/60. 'No services' (18%) and 'cannot afford' (18%) were mentioned most as reasons why surgery had not been done, followed by 'no information' (13%), 'waiting for maturity' (12%) and 'old age, no need for surgery' (12%). CONCLUSION: The number of cataract operations in Chakwal District can be increased by reducing the threshold for cataract surgery to VA < 6/60 or less. A special approach to operate more females may be required. Results from this survey can be used for a planning exercise to optimize eye care services in the district. Sustained efforts have to be made to increase the number of IOL surgeries, through making IOL surgery available locally at an affordable cost.

Aged↗

PubMed2003

Cataract blindness in Paraguay--results of a national survey.

PURPOSE: To estimate the burden of visual loss and blindness due to cataract in people aged 50 years and over in Paraguay. METHODS: Forty clusters of 60 persons each who were 50 years and older (2400 eligible persons) were selected by systematic random sampling from the entire population of Paraguay. A total of 2136 persons were examined (89% coverage). RESULTS: For the population 50 years and over, the age- and gender-adjusted prevalence of bilateral blindness (VA < 3/60 with available correction) was 3.14% (95% CI: 2.2-4.4). The adjusted prevalence of bilateral cataract blindness (VA < 3/60) was 2.01% (95% CI: 1.3-3.0), making cataract the major cause of bilateral blindness in this age group (64%). The adjusted prevalence of bilateral severe visual impairment (VA < 6/60 with available correction) was 5.17% (95% CI: 3.9-6.7) and the adjusted prevalence of severe visual impairment due to bilateral cataract (VA < 6/60) was 3.09% (95% CI: 2.2-4.3). The cataract surgical coverage (persons) was 44% for bilaterally blind persons with VA < 3/60; 36% for persons with bilateral VA < 6/60; and 28% for any eye with VA < 6/60 due to cataract. With IOL implantation, 77% of the operated eyes could see 6/18, against 46% of the non-IOLs (p < 0.005), a significant better outcome. CONCLUSION: There is a need to increase the cataract surgical coverage in Paraguay. The number of eye surgeons is adequate but the accessibility of cataract surgical services in rural areas and the affordability of surgery to large sections of society are major constraints.

Aged↗

PubMed2003

Cataract.

Explore the source record for details and available documents.

Blindness↗

PubMedDate not supplied

[Cataract blindness in people 50 years old or older in a semirural area of northern Peru].

OBJECTIVE: To determine the prevalence of blindness and of cataract blindness in persons 50 years of age or older in Piura and Tumbes, which are two departments in northern Peru, and to describe the coverage and quality of cataract surgery services in that area, and the barriers that prevent access to those services. METHODS: Systematic sampling of persons 50 years old or older was done in Piura and Tumbes between August 2002 and March 2003, with 80 clusters of 60 people each being selected. Of the 4 800 persons chosen, 4,782 of them were examined, using a survey instrument that gathered general information on each person, the results of the visual acuity test and the lens examination, and information on cataract surgery or why that surgery had not been done. Visual acuity (VA) testing was done with a Snellen optotype with the letter "E," with sizes of 20/60 and 20/200 at distances of 6 m and 3 m, respectively, with the person using the visual correction (glasses) available. When the VA was less than 20/60 in one of the eyes, vision was tested with pinhole glasses. RESULTS: The prevalence of bilateral blindness (VA < 20/400) due to cataract, adjusted by age and sex, was 2.1% (95% confidence interval (CI): 1.7% to 2.6%). Among the 193 persons with bilateral blindness due to any cause, cataract was the cause in 104 of them (53.9%). The prevalence of blindness due to cataract or other causes increased with age and was higher in women than in men. Only 25% of the persons studied who needed cataract surgery had had that done. The prevalence of bilateral VA less than 20/200 due to unoperated cataract was 6.3% (95% CI: 5.3% to 7.3%); only 12% of the persons with that level of visual deficiency had had cataract surgery. The VA of 26% of the eyes operated on for cataract was lower than 20/200. The reasons given by persons who needed cataract surgery but who had not had it included not being able to pay for the operation (28%), lack of knowledge concerning cataracts (25%), fear of the operation (23%), and fear of completely losing their sight (17%). CONCLUSIONS: Most of the cases of blindness and of serious deficiency in visual acuity in persons 50 years old or older in Piura and Tumbes are due to uncorrected refractive defects, especially cataracts. The high prevalence of bilateral blindness due to cataracts (2.1%) could be reduced with measures that facilitate access to appropriate treatment.

Aged↗