DESIGN: Population-based incidence study using data from a medical savings fund.
STUDY POPULATION: Chinese, Malay, and Indian residents in Singapore.
METHODS: Data on all cataract operations performed for "senile cataract" (International Classification of Diseases, Ninth Revision, Clinical Modification code 366.1) between 1991 and 1996 were retrieved from Medisave, a population-wide, government-administered medical savings fund. The Singapore census was used as a denominator to allow an estimation of age, sex, and race-specific annual rates of cataract surgery.
RESULTS: Between 1991 and 1996, 61 210 cataract operations for "senile cataract" were performed on Singapore residents, which is equivalent to an average rate of 356.4 cataract operations per 100 000 persons per year (95% confidence interval [CI], 353.6-359.2). The average rate was highest for Indians (age-sex adjusted rate of 396.5 per 100 000/year), followed by Chinese (371.2 per 100 000/year), and lowest for Malays (237.2 per 100 000/year). Women had higher rates of cataract extraction than men (age-adjusted relative risk, 1.14; 95% CI, 1.11-1.17), with this pattern consistent across the 3 racial groups. The rate of cataract extraction increased by an average of 40 operations per 100 000/year (95% CI, 28.6-52.8) between 1991 and 1996. Overall, the proportion of cataract extraction without concurrent intraocular lens implantation was low (n = 762, 1.2%), but rates still decreased by an average of 0.8 per 100 000 per year (95% CI, 0.03-1.5) during the 6 years.
CONCLUSIONS: The rate of cataract extraction in Singapore is consistent with rates seen in developed countries in the West. Racial variation in rates suggests varying predisposition to cataract development and/or threshold for cataract surgery between Chinese, Malay, and Indian populations in Singapore.
METHODS: The English version of Catquest-9SF questionnaire was translated and back translated into Malay and Chinese languages. The Malay and Chinese translated versions were self-administered by 236 and 202 pre-operative patients drawn from a cataract surgery waiting list, respectively. The translated Catquest-9SF data and its four response options were assessed for fit to the Rasch model.
RESULTS: The Catquest-9SF performed well in the Malay and Chinese translated versions fulfilling all criteria for valid measurement, as demonstrated by Rasch analysis. Both versions of questionnaire had ordered response thresholds, with a good person separation (Malay 2.84; and Chinese 2.59) and patient separation reliability (Malay 0.89; Chinese 0.87). Targeting was 0.30 and -0.11 logits in Malay and Chinese versions respectively, indicating that the item difficulty was well suited to the visual abilities of the patients. All items fit a single overall construct (Malay infit range 0.85-1.26, outfit range 0.73-1.13; Chinese infit range 0.80-1.51, outfit range 0.71-1.36), unidimensional by principal components analysis, and was free of Differential Item Functioning (DIF).
CONCLUSIONS: These results support the good overall functioning of the Catquest-9SF in patients with cataract. The translated questionnaire to Malay and Chinese-language versions are reliable and valid in measuring visual disability outcomes in the Malaysian cataract population.
METHODS: The Malay version was translated by two independent translators who were well versed in both languages. We carried out a cross-sectional study collecting data between June 2017 and March 2018 in the pre-operative Eye Clinic of Hospital Melaka with 224 respondents (mean age 66.8 years) and another 204 respondents (mean age 64.3 years) participating in the English version and Malay version of the Questionnaire respectively. Methods used to validate the standard questionnaire included the use of construct validity via factor analysis and the deployment of reliability test through assessment of internal consistency via Cronbach's alpha.
RESULTS: We observed both English and Bahasa Malaysia versions to have high reliability with Cronbach's alpha values of 0.90 and above in factors on difficulty with activities and responses to vision problems. Exploratory factor analysis performed revealed that the three-factor model fits the data well for the English version of the questionnaire - difficulty with activities (23.81 % of variance), responses to vision problem (22.22 % of variance) and general health and vision (14.68 % of variance). The Bahasa Malaysia version of the questionnaire produced three factors with two of the factors resembling the factors from the original version of the questionnaire - difficulty with activities (24.3 % of variance) and responses to vision problem (23.7 % of variance). Item response theory analysis revealed that these factors for both English and Bahasa Malaysia versions comprised of adequately fitted items.
CONCLUSION: The present study observed that both the English and Bahasa Malaysia versions of the NEI VFQ-25 have comparable construct validity to the original American version. With high validity and reliability, the tool shall be able to provide health care providers the assessment of impact due to cataract and other ophthalmic conditions on the vision-related quality of life of ophthalmic patients.