2.1 Participants and procedure
This study employed a cross-sectional survey design utilizing both convenience and purposive sampling methods. The target population consisted of older adults with low vision who were followed up at the ophthalmology clinics of two tertiary-level hospitals in Chongqing, Western China, from October 2020 to March 2021. According to the estimation requirements of sample size for cross-sectional surveys, that is, the sample size should be 5–10 times the number of scale items[10], the scale with the largest number of items in this study is the social participation scale, with a total of 46 items, according to the number of items 5–10 times the estimate, and considering the dropout of the sample size, it was expanded by 10%, and the sample size was estimated to be at least 253 cases. Ultimately, 277 questionnaires were distributed; however, three participants withdrew during the survey, leading to a final count of 274 valid responses.
The inclusion criteria for the study population were as follows: 1) individuals aged 65 years or older; 2) residents of the main urban area of Chongqing City for at least one year; 3) a clear diagnosis of visual impairment in accordance with the 2019 WHO Visual Impairment Classification Criteria[1], defined as a Presenting Visual Acuity (PVA) in the better eye of less than 0.5 but greater than 0.05); 4) diagnoses related to age-related visual impairment, including macular degeneration, glaucoma, retinal diseases, optic nerve diseases, high myopia fundopathy, and failure to improve visual function following cataract surgery; 5) presence of eye diseases that cannot be treated or corrected through refraction, surgery, or medication; and 6) voluntary participation in the study after a detailed explanation of the informed consent form.
The exclusion criteria included: 1) individuals with severe hearing impairment or concurrent psychological disorders; 2) those with other serious systemic diseases; 3) individuals who required eye surgery in the near future; 4) those in the surgical or terminal stages of illness; and 5) individuals unable to communicate effectively, which hindered their ability to cooperate with the completion of the survey.
Prior to administering the questionnaire survey, the head nurse of the department was contacted to obtain permission and support. The purpose, content, and significance of the study were clearly explained to the respondents who met the criteria for nativity. Following this, the questionnaire was administered in the study room of the ophthalmology outpatient clinic after securing their consent. Given that the respondents were elderly individuals with low vision, which may hinder their ability to read the questionnaire entries, a one-on-one, question-by-question interview format was employed to collect the data. The researcher maintained a neutral tone of voice while reading the questions and accurately recording the responses. This study received approval from the Ethics Committee of the Army Medical University (approval number 2020-013-02).
2.2 Measurements
2.2.1 Sociodemographic characteristics
The socio-demographic characteristics of this study included six dimensions such as gender, literacy, mode of residence, marital status, economic income, and presence of chronic diseases.
2.2.2 Memorial University of Newfoundland Scale of Happiness (MUNSH)
The MUNSH comprises a total of 24 entries, serving as a comprehensive reflection of both the short-term emotional responses and long-term emotional experiences of the study participants across four dimensions: positive affect (PA), negative affect (NA), positive experience (PE), and negative experience (NE)[11]. Scores of 36 or higher indicate a higher level of subjective well-being (SWB), scores of 12 or lower indicate a low level of SWB, while scores falling between these two thresholds represent a moderate level of SWB[11]. In this study, the Cronbach's alpha for the scale was 0.899.
2.2.3 Community Participation Index (CPI)
The 46-item scale assesses individual self-reported frequencies of social participation activities alongside subjective feelings regarding social participation[12]. In this study, the Cronbach's alpha was measured at 0.839. Social participation activities were categorized into three main groups: family activities, social and recreational activities, and work role activities. A score of 0 was assigned for 'no' participation, with higher scores reflecting increased frequency of participation. The subjective feelings of social participation encompass perceived importance and controllability, where higher scores indicate that individuals perceive or experience greater restrictions on social participation, suggesting a poorer overall experience of social participation[12].
2.2.4 Social Support Rating Scale (SSRS)
The Social Support Rating Scale (SSRS) quantitatively evaluates an individual's level of social support across three dimensions: objective support, subjective support, and utilization of support. This scale consists of 10 items, with scores ranging from 12 to 66; higher scores indicate a greater level of social support[13]. In this study, Cronbach's α was found to be 0.902, reflecting a high level of internal consistency.
2.2.5 National Eye Institute Visual Function Questionnaire (NEI-VFQ-25)
This multidimensional questionnaire evaluates the capacity to perform vision-related activities of daily living and assesses changes in emotional and social functioning following vision loss[14]. It is generally recommended for studies involving older populations. The questionnaire comprises 25 self-reported items that encompass 12 dimensions. Higher scores reflect a better quality of life associated with visual function[14]. Due to the fact that individuals with low vision cannot drive[15], the item regarding driving was excluded from the questionnaire. In this study, Cronbach's α was found to be 0.917.
2.3 Data analysis
Data entry and collation were performed using Epidata 3.1 and Excel software, while the questionnaire data were analyzed with SPSS version 23.0 after thorough verification. The demographic characteristics, subjective well-being, frequency of socially engaged activities, and feelings of social engagement among respondents were statistically analyzed using means and standard deviations. To examine differences in subjective well-being among older adults with low vision across various demographic control variables, t-tests and one-way ANOVA were employed. Pearson correlation analysis was conducted to assess the relationships between social participation activities, subjective feelings of social participation, and each of the study variables individually. Additionally, multiple mediation effects modeling was utilized, grounded in theoretical frameworks regarding the impact of social support and quality of life related to visual function on health outcomes. After controlling for statistically significant demographic variables (p < 0.05), linear regression analysis was performed to evaluate the validity of the predictive model. The bootstrap method was applied to assess the mediating effects, with significance determined when the 95% confidence interval excluded zero. This analysis was executed using SPSS PROCESS version 3.0 software