The Nigerian national blindness and visual impairment survey: Rationale, objectives and detailed methodology.

BACKGROUND: Despite having the largest population in Africa, Nigeria has no accurate population based data to plan and evaluate eye care services. A national survey was undertaken to estimate the prevalence and determine the major causes of blindness and low vision. This paper presents the detailed methodology used during the survey. METHODS: A nationally representative sample of persons aged 40 years and above was selected. Children aged 10-15 years and individuals aged <10 or 16-39 years with visual impairment were also included if they lived in households with an eligible adult. All participants had their height, weight, and blood pressure measured followed by assessment of presenting visual acuity, refractokeratomery, A-scan ultrasonography, visual fields and best corrected visual acuity. Anterior and posterior segments of each eye were examined with a torch and direct ophthalmoscope. Participants with visual acuity of < = 6/12 in one or both eyes underwent detailed examination including applanation tonometry, dilated slit lamp biomicroscopy, lens grading and fundus photography. All those who had undergone cataract surgery were refracted and best corrected vision recorded. Causes of visual impairment by eye and for the individual were determined using a clinical algorithm recommended by the World Health Organization. In addition, 1 in 7 adults also underwent a complete work up as described for those with vision < = 6/12 for constructing a normative data base for Nigerians. DISCUSSION: The field work for the study was completed in 30 months over the period 2005-2007 and covered 305 clusters across the entire country. Concurrently persons 40+ years were examined to form a normative data base. Analysis of the data is currently underway. CONCLUSION: The methodology used was robust and adequate to provide estimates on the prevalence and causes of blindness in Nigeria. The survey would also provide information on barriers to accessing services, quality of life of visually impaired individuals and also provide normative data for Nigerian eyes

Causes of poor outcome after cataract surgery in Satkhira district, Bangladesh.

AIMS: Recent data have raised concerns about visual outcome following cataract surgery. The aim of this study was to assess the frequency and causes of poor and borderline outcome after cataract surgery in a population-based case series in Satkhira district, Bangladesh. METHODS: A population-based case series was conducted within a population-based cluster survey of people aged over 50 years in Satkhira district where 4868 people underwent visual acuity (VA) screening. Eyes operated for cataract with VA6/18) for 128 eyes (60.1%), borderline (VA<6/18 to 6/60) for 35 eyes (16.4%), and poor (VA<6/60) for 50 eyes (23.5%) with available correction. Borderline and poor outcomes were most commonly due to lack of spectacles (25.8%), poor selection (33.8%), or surgical complications (30.6%). Surgical sequelae, namely posterior capsule opacification, was a less common cause of poor or borderline outcome (9.7%). CONCLUSIONS: Quality of surgical outcomes is of concern in Satkhira district. Increased emphasis on selection of subjects for surgery, provision of spectacles, and monitoring of surgery may improve outcomes