Visual impairment and blindness: Trends in multi-ethnic Singapore
Presenting and best-corrected bilateral visual impairment (VI) and blindness are uncommon among Singaporeans, according to a new study. Important risk factors include the Malay ethnicity and advanced age and cataracts.
Drawing from the Singapore Epidemiology of Eye Diseases study, researchers identified 10,020 participants (mean age, 58.9±10.4 years; 50.7 percent female) who all underwent standardized eye examinations. VI was defined as having visual acuity (VA) <20/40 to ≥20/200. On the other hand, VA <20/200 was classified as blindness.
Of the participants, 3,269 were Malay (mean age, 59.2±11.0 years), who tended to be older than the other ethnic groups. There were 3,400 Indians (mean age, 57.8±10.1 years) and 3,351 Chinese (mean age, 59.7±9.9 years). All groups were comparable in terms of sex distribution. Based on the presenting VA (PVA), the age-standardized prevalence of bilateral blindness in the overall cohort was 0.9 percent. [Am J Ophthalmol 2019;doi:10.1016/j.ajo.2019.05.006]
In comparison, the corresponding rates for bilateral VI, unilateral blindness and unilateral VI were 18.4 percent, 1.8 percent and 18.5 percent.
Basing the criteria on best-corrected VA (BCVA), the age-standardized prevalence rates of bilateral blindness, bilateral VI, unilateral blindness and unilateral VI were 0.3 percent, 4.2 percent, 1.6 percent and 6.8 percent, respectively.
Disaggregation according to the three ethnic groups showed that presenting bilateral blindness was most common in Malays as opposed to Indians and Chinese (age-standardized prevalence rates: 1.4 percent vs 0.7 percent and 0.5 percent; p<0.001 for both). The same was true for presenting bilateral VI (19.9 percent vs 18.0 and 17.2 percent).
Best-corrected bilateral VI likewise occurred with significant frequency in Malays than in Indians and Chinese (5.4 percent vs 3.6 percent and 3.3 percent; p<0.001 for both).
In contrast, the prevalence of unilateral blindness was significantly elevated in participants of either Indian and Chinese descent (2.1 percent for both) as opposed to Malays (1.3 percent; p<0.001 for both). Moreover, unilateral VI was significantly more common among Chinese participants than in Indians and Malays (20.9 percent vs 18.0 percent and 16.5 percent; p<0.001 for both).
In terms of causes, cataract was the top factor for bilateral blindness (61.5 percent; n=67) and was second only to uncorrected refractive error (55.8 percent; n=1,202) for bilateral VI (34.1 percent; n=735). This trend was consistent across all three ethnic groups examined.
“In totality, this thesis provides the first large population-based summary of trends and risk factors associated with VI and blindness in a multi-ethnic Asian population in Singapore, using multifaceted evaluations and analyses, and providing new insights on traits related to visual loss in Asians,” said researchers.
“Collectively, these findings will be useful for the planning of eye health services, and designing of relevant interventions for Asia’s rapidly developing urban communities, in a bid to reduce the burden of VI and blindness,” they added.
“Further collaborations between research groups to combine data and to perform meta-analysis on VI remain necessary to advance the research and the understanding on the magnitude of VI in Asia, in particular urban communities where data remain scarce,” researchers said.