Causes of blindness and visual impairment in Pakistan. The Pakistan National Blindness and Visual impairment Survey.
- Brendan Dineen (brendan.dineen{at}lshtm.ac.uk),
- Rupert Richard Bourne (rupert.bourne{at}lshtm.ac.uk),
- Zahid Jadoon (zahid{at}pico.org.pk),
- Shaheen Pravin Shah (shaheen.shah{at}lshtm.ac.uk),
- Mohammad A Khan,
- Allen Foster,
- Clare E Gilbert,
- Mohammad D Khan
- International Centre for Eye Health, London School of Hygiene and Tropical Medicine, United Kingdom
- International Centre for Eye Health, London School of Hygiene and Tropical Medicine, United Kingdom
- Pakistan Institute of Community Ophthalmology, Kyber Institute of Ophthalmic Medical Sciences, Pakistan
- London School of Hygiene and Tropical Medicine, United Kingdom
- Pakistan Institute of Community Ophthalmology, Kyber Institute of Ophthalmic Medical Sciences, Pakistan
- International Centre for Eye Health, London School of Hygiene and Tropical Medicine, United Kingdom
- International Centre for Eye Health, London School of Hygiene and Tropical Medicine, United Kingdom
- Pakistan Institute of Community Ophthalmology, Kyber Institute of Ophthalmic Medical Sciences, Pakistan
- Published Online First 17 January 2007
Abstract
Purpose: To determine the causes of blindness and visual impairment in adults (≥30 years old) in Pakistan, and to explore socio-demographic variations in cause.
Methods: Multi-stage, stratified, cluster random sampling survey was used to select a nationally representative sample of adults. Each subject was interviewed, had their visual acuity measured, underwent autorefraction and fundus/optic disc examination. Those that saw < 6/12 in either eye underwent a more detailed ophthalmic examination. Causes of visual impairment were classified according to the accepted WHO methodology. An exploration of demographic variables was conducted using regression modeling.
Results: A sample of 16,507 adults (95.5% of those enumerated) was examined. Cataract was the most common cause of blindness (51.5%; defined as <3/60 in the better eye on presentation) followed by corneal opacity (11.8%), uncorrected aphakia (8.6%) and glaucoma (7.1%). Posterior capsular opacification accounted for 3.6% of blindness. Among the moderately visually impaired (<6/18 to ≥6/60), refractive error was the most common cause (43%), followed by cataract (42%). Refractive error as a cause of SVI/BL was significantly higher in rural dwellers than in urban dwellers (OR 3.5, 95%CI: 1.1, 11.7). Significant provincial differences were also identified. Overall we estimate that 85.5% of causes were avoidable and that 904,000 adults in Pakistan have cataract (<6/60) requiring surgical intervention.
Conclusions: This comprehensive survey provides the reliable estimates of the causes of blindness and visual impairment in Pakistan. Despite expanded surgical services, cataract still accounts for over half of the blindness in Pakistan. One in eight blind adults has visual loss from sequelae of cataract surgery. Services for refractive errors need to be further expanded and integrated into eyecare services, particularly those serving rural populations.
