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M. Wu, J. L. Y. Yip, H. Kuper, S. Polack, A. Foster; Is All Cataract Blindness Avoidable?. Invest. Ophthalmol. Vis. Sci. 2007;48(13):323.
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© ARVO (1962-2015); The Authors (2016-present)
To determine the prevalence of cataract blindness from a Rapid Assessment of Avoidable Blindness (RAAB) survey in Kunming, south-west China, and to estimate the proportion of cataract blind that may not be avoidable.
A sample size of 2760 was estimated from an expected blindness prevalence of 2.3% in adults aged 50 years and over; a precision of 30% and an expected design effect (DEFF) of 1.4 for cluster size of 60 was used. Forty six clusters in the Kunming city district were randomly selected using probability proportional to size methodology. Individual participants from each cluster were selected using compact segment sampling (CSS) or quota sampling when CSS was not logistically feasible. Survey fieldwork took place between June and August 2006. Two ophthalmologists and their teams used an established standardised protocol for a RAAB survey to determine the population prevalence of cataract blind. The lens was examined with a bright torch or a direct ophthalmoscope. In addition, the pupils were tested for an afferent or a relative afferent pupillary defect using a bright torch and the swinging flashlight method in all participants diagnosed with blindness due to cataract. The prevalence of blindness was calculated using the RAAB package. Blindness was defined as presenting visual acuity (PVA) in the better eye of ≤3/60. Severe visual impairment (SVI) was defined as PVA ≤ 6/60, and visual impairment (VI) as PVA ≤6/18.
Out of 2760 enumerated participants, 2558 (93.8%) were examined during the survey. Blindness was detected in 95 out of 2558, which gives a crude blindness prevalence estimate of 3.7% (95% CI: 2.4-4.0, DEFF=1.6); the age and sex adjusted prevalence was 2.3%. The prevalence of SVI was 2.5% (1.5-4.0%) and VI was 9.1% (7.5-10.7). Sixty out of 2558 (2.3%, 1.7-2.9%) were diagnosed as cataract blind, which represents 63.2% of cases with blindness. An abnormal pupillary reaction was detected in 10 out of 60 (16.7%) participants with cataract blindness.
An estimated 16.7% of participants diagnosed with cataract blindness had an abnormal pupillary reaction in this large survey from southwest China. Cataract is an avoidable cause of blindness. However, the presence of a pupillary defect indicates ocular co-morbidity, and blindness in these cases may not be avoidable. Vision 2020 initiatives direct resources into programs that aim to eliminate avoidable blindness based on needs assessments. Extrapolations to predict global estimates of avoidable blindness and resource allocation using rapid assessment techniques should be taken with care.Characters: 2227 (max= approx 2250)
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