Purpose:
To quantify the eye disease-specific impact of unilateral and bilateral vision impairment (VI) on vision-specific functioning (VF) in ethnic Indians living in Singapore.
Methods:
Ethnic Indians aged 40 years and older participated in the Singapore Indian Eye Study (SINDI), and underwent standardized ophthalmic assessments for VI and blindness, defined using presenting visual acuity (PVA) according to the United States (U.S) definition. Sociodemographic data were recorded using a standardized questionnaire. Rasch analysis was used to validate the VF-11 and determine its psychometric properties. The major causes of vision impairment (i.e., cataract, refractive error, age-related macular degeneration, diabetic retinopathy [DR] and glaucoma) were determined by ophthalmologists at examination. Multivariate linear regression analysis and predicted probability were performed to assess the impact of VI on the overall VF score, derived from Rasch analysis.
Results:
There were 3396 persons available for analyses. The overall mean±SD VF score was 4.62±1.20 logits. After adjusting for sociodemographic factors (e.g., age, gender, education, literacy, migration status), participants with VI had a dose-dependent reduction in VF score compared to those with normal vision in both eyes, ranging from -11.2% normal vision in one eye, low vision in the other (confidence interval [CI] -12.2%, -10.3%, p<0.001), -12.7% blindness in one eye, normal vision in the other (CI -15.1%, -10.4%, p<0.001), -19.4% low vision in both eyes (CI -20.8%, -18.1%, p<0.001), -52.9% blindness in one eye, low vision in other (CI -55.3%, -50.4%, P<0.001), to -77.2% blindness in both eyes (CI -82.4%, -72.0%, p<0.001). The impact of VI on VF score varied across different major causes of vision loss regardless of socioeconomic factors (e.g., education, income, literacy). Specifically, VI attributed to cataract in one or both eyes had a significant decrease in VF score by 17.7% and 22.3% respectively, compared to those with normal vision in both eyes (p<0.001). The impact of unilateral and bilateral VI on VF score was greater in participants with glaucoma (32.2% in unilateral VI and 35.9% in bilateral VI, p<0.001) and DR (29.4% in unilateral VI and 33.3% in bilateral VI, p<0.001).
Conclusions:
VI and major age-related eye diseases such as cataract, DR, and glaucoma are significantly associated with poorer deterioration in VF, regardless of education level, literacy adequacy, immigration pattern. Glaucoma and DR appeared to have a greater negative impact on VF score compared to cataract. Our study highlights the importance of disease-specific interventions in reducing the adverse impact of VI on daily activities.