Rapid Assessment of Avoidable Blindness in Kunming, China
Presented in part at: Association for Research in Vision and Ophthalmology Annual Meeting, May 2007, Fort Lauderdale, Florida.
Received 27 March 2007; received in revised form 13 July 2007; accepted 1 August 2007. published online 22 October 2007.
Objective
To estimate the magnitude and causes of visual impairment (VI) in people aged ≥ 50 years in Kunming using the Rapid Assessment for Avoidable Blindness methodology, and to assess the prevalence of a pupillary defect in participants diagnosed as cataract visually impaired.
Design
Population-based cross-sectional survey.
Participants
We enrolled 2760 residents of Kunming prefecture in southwest China, >50 years of age.
Methods
Forty-six clusters of 60 people were selected based on population proportional to size. Households from each cluster were selected using compact segment sampling (CSS) or quota sampling when CSS was not feasible. Visual acuity (VA) was assessed using a tumbling E chart. Lens status and cause of VI were determined by ophthalmologists using direct ophthalmoscopy through a dilated pupil where necessary. The pupillary reaction was assessed on undilated pupils when VI was detected.
Main Outcome Measures
Prevalence of blindness (VA<3/60), severe VI (SVI) (VA<6/60), and VI (VA<6/18) using presenting VA (PVA). The causes of blindness and VI and prevalence of a pupillary defect in the cataract visually impaired were also assessed.
Results
Of 2760 enumerated residents, 2588 were examined. The sample prevalence of bilateral blindness was 3.7% (95% confidence interval [CI], 2.8–4.6%). The prevalence of SVI was 3.0% (95% CI, 2.2–3.8%), and of VI was 9.1% (95% CI, 7.5–10.7%). The main cause of blindness was cataract (63.2% of blindness), followed by nontrachomatous corneal scar (14.7%), glaucoma (7.4%), and other posterior segment disease/neurologic disorders (4.2%). A pupillary defect was detected in 16% of those diagnosed with cataract VI. The cataract surgical coverage in the bilaterally blind was 58.9%, and 45% of operated eyes had good outcome with available correction (VA>6/18). The main barrier to cataract surgery was cost.
Conclusions
Cataract remains the most important cause of preventable blindness in this poor region of China, and affordable provision of surgery would help to address this problem. Some cases of cataract blindness may not be preventable owing to preexisting comorbidity, as detected by the presence of a pupillary defect.
2International Centre for Eye Health, London School of Hygiene & Tropical Medicine, London, United Kingdom.
3Department of Epidemiology, Institute of Ophthalmology, University College London, United Kingdom.
Correspondence to Jennifer L. Y. Yip, MBBS, MSc, London School of Hygiene & Tropical Medicine, Keppel Street, London WC1E 7HT, United Kingdom.
Manuscript no. 2007-412.
Supported by grants from Swire Foundation, London, United Kingdom; ORBIS International, London, United Kingdom; and Christian Blind Mission, Bensheim, Germany.
ABSTRACT