To investigate the prevalence of cataract, cataract surgical coverage and surgical outcomes in people aged 50 years and older in Kandze Tibetan areas of Sichuan Province, and to evaluate the effectiveness of the prevention and treatment of blindness in the region.

A cross-sectional study was conducted to study the population aged 50 years and above in Ganzi Tibetan Autonomous Prefecture, Sichuan Province, from October 2017 to April 2018 using the Rapid Assessment of Avoidable Blindness (RAAB) method.A total of 5 000 permanent residents aged 50 years and older were selected using a stratified, cluster sampling method with reference to the data from the 2010 China Population Census with the RAAB software, and each cluster consisted of 50 people, for a total of 100 clusters.The survey was conducted by two survey teams, and all subjects underwent visual acuity and ophthalmic examinations at home to investigate relevant cataract prevalence, surgical coverage, surgical barriers, and postoperative outcomes according to WHO Standards.This study adhered to the Declaration of Helsinki.The study protocol was approved by the Ethics Committee of Kandze Prefecture People's Hospital (No.GZZYY-2016-11). Written informed consent was obtained from each subject.

Of 5 000 eligible participants, 4 763 were examined, with a response rate of 95.3%.Referred to the visual impairment standard of WHO and the pinhole visual acuity, the prevalence of bilateral blindness, severe, moderate and mild visual impairment was 0.6%(95% [confidence interval, CI]: 0.4%-0.9%), 0.9%(95% CI: 0.6%-1.2%), 2.4%(95% CI: 2.0%-2.9%) and 5.2%(95% CI: 4.6%-5.9%), respectively.The prevalence of cataract blindness was 0.7%(95% CI: 0.4%-1.0%) in females, significantly higher than 0.2%(95% CI: 0.1%-0.5%) in males(P<0.05). The prevalence of cataract blindness was 2.3% among Tibetan, higher than 1.0% among Han Chinese, showing a statistically significant difference (P<0.05). By the number of eyes, the cataract surgical coverage was 60.8%(95% CI: 55.5%-65.8%) in females, which was lower than 70.1%(95% CI: 63.7%-75.7%) in males, with a statistically significant difference (P<0.05). By the number of cases, the surgical coverage for cataract blindness in both eyes was 82.0%(95% CI: 75.2%-87.6%), with blindness defined as the pinhole visual acuity <0.05 in the dominant eye.A total of 171 people with untreated cataract received a questionnaire about barriers to cataract surgery.The most important barrier was unaware that treatment was available at 77.8%, followed by inconvenient transportation or being unaccompanied to the hospital at 11.7%.A total of 364 eyes underwent cataract surgery, of which 336 eyes underwent intraocular lens implantation, and the intraocular lens implantation rate was 92.3%.There were 216 eyes with a postoperative cataract visual acuity ≥0.3, accounting for 59.3%(216/364).

In the Kandze Tibetan area of Sichuan Province, cataract is still the main cause of blindness among people aged 50 and above, and surgery for cataract remains the focus of blindness prevention work.The cataract surgical coverage in this area is high, but the postoperative outcomes are still poor compared with the WHO reference index for post-cataract surgery (1998), and corresponding measures must be taken to improve the quality of surgery.

Cataract; Prevalence; Surgery; Health survey; Rapid Assessment of Avoidable Blindness; Kandze Tibetan areas; China