Dineen Brendan, Foster Allen, Faal Hannah
International Centre for Eye Health, London School of Hygiene and Tropical Medicine, London, UK.
Ophthalmic Epidemiol. 2006 Feb;13(1):31-4. doi: 10.1080/09286580500473787.
To determine whether a sample of the 50-year-old and above population would provide comparable information to a total population-based survey.
In 1996, a national eye survey of the total population in The Gambia was undertaken and the results concerning the prevalence and distribution of blindness and low vision have been reported. The same data set was used to analyse the prevalence and causes of blindness and low vision in people aged 50 years and above, and to compare the findings with the total population.
Of 55 bilaterally blind people in the total population, 83.6% were 50 years of age or older. The distribution by cause of blindness was similar for the total population and for those aged 50 years and above. Cataract and uncorrected aphakia accounted for 46% and 13%, respectively, in the total population and 48% and 15% in the 50 year and above age group. Trachoma accounted for 5% and 4%, and other corneal opacities for 16% and 13%, respectively. Phthisis bulbi, which may follow perforated corneal ulcers, ocular trauma/surgery or occasionally severe uveitis, accounted for 4% in both age groups, and glaucoma accounted for 9% in the total population and 11% in the 50 year plus group.
Assessment of the 50 year and above age group proved to be a good indicator for the causes of blindness and visual impairment in the total population and for determining those causes of blindness that are avoidable. Such an assessment requires a much smaller sample size, less than 20% of the sample size for the total population, and is likely to be less expensive.
确定50岁及以上人群样本能否提供与基于全人群的调查可比的信息。
1996年，在冈比亚开展了一项全国性全人群眼部调查，关于失明和视力低下的患病率及分布情况的结果已发表。使用同一数据集分析50岁及以上人群失明和视力低下的患病率及病因，并将结果与全人群进行比较。
在全人群的55例双侧失明者中，83.6%为50岁及以上。全人群和50岁及以上人群失明病因的分布相似。在全人群中，白内障和未矫正无晶状体分别占46%和13%，在50岁及以上年龄组中分别占48%和15%。沙眼分别占5%和4%，其他角膜混浊分别占16%和13%。眼球痨（可继发于角膜溃疡穿孔、眼外伤/手术或偶尔的严重葡萄膜炎）在两个年龄组中均占4%，青光眼在全人群中占9%，在50岁及以上组中占11%。
对50岁及以上年龄组的评估被证明是全人群失明和视力损害病因以及确定可避免失明病因的良好指标。这样的评估所需样本量小得多，不到全人群样本量的20%，而且成本可能更低。
