The Prevalence and Incidence of Depression among Visually Impaired People: A Systematic Review and Meta-Analysis Protocol

Introduction

Visual impairment is the third leading cause of disability globally. As of 2020, approximately 1.1 billion individuals worldwide have been affected by some degree of visual impairment. When categorized by severity, an estimated 295 million people (3.5% of the global population) experience moderate to severe vision impairment, 258 million (3.3%) have mild vision impairment, 510 million (6.5%) have near vision impairment, and 43 million (0.5%) are blind. Notably, at least 771 million cases (90%) of visual impairment globally are preventable or treatable.¹

Eye health refers to the enhancement of vision, ocular well-being, and functional ability, all of which contribute to overall health, well-being, social inclusion, and quality of life. It is a vital component in achieving several Sustainable Development Goals (SDGs). Conversely, compromised eye health and vision impairment adversely affect quality of life and hinder equitable access to education and employment opportunities.²

In addition, it is linked to decreased functional capacity, greater disability, a higher risk of falls, social isolation, institutionalization, and increased mortality. The global economic burden of visual impairment exceeds US$3 trillion annually, impacting patients, their families, and communities. Beyond its direct effects on vision, visual impairment also impedes societal development and progress, affecting both local communities and the broader population.³

Visual impairment can have significant impacts on physical health, quality of life, and mental well-being. A recent systematic review found that vision impairment serves as indicators of frailty in community-based studies, with depression being a major associated condition.⁴

Depression is notably prevalent among individuals with visual impairment. According to a recent study by the Centers for Disease Control and Prevention (CDC), approximately one in four adults with visual impairment reported experiencing depression. Moreover, younger adults with visual impairment were found to have nearly five times the risk of developing severe depression compared to older adults.⁵ However, prevalence estimates vary widely, ranging from 14% to 44%, depending on the specific population studied.

Depression constitutes a prevalent mental health disorder, characterized by a sustained state of low mood or emotional despondency, accompanied by anhedonia or a diminished capacity to derive pleasure from previously enjoyable activities. It is further typified by pervasive feelings of guilt or worthlessness, a marked decline in energy levels, difficulty concentrating, changes in appetite, psychomotor slowing or restlessness, sleep disturbances, persistent suicidal thoughts, recurrent over a protracted period.⁶

According to a report by the World Health Organization, an estimated 322 million individuals globally are impacted by depression, representing roughly 4.4% of the world’s population. The prevalence of this pervasive mental disorder is increasing, with a particularly pronounced rise observed in low- and middle-income countries.⁷ Depression can significantly impact various aspects of an individual’s well-being, including interpersonal relationships, academic performance, and occupational functioning.⁶

Several studies have indicated a strong association between visual impairment and depression, with individuals having vision impairment being more vulnerable to developing depressive symptoms.^8–11 Though, the global epidemiology of depression among individuals with visual impairment remains limited, with variations in prevalence and incidence estimates across different populations and study methodologies.

This systematic review and meta-analysis protocol aims to assess the global prevalence and incidence of depression among individuals with visual impairment. By systematically reviewing and quantitatively synthesizing existing studies, this review will enhance understanding of the mental health burden associated with visual impairment, inform public health initiatives, and guide future research and interventions for this at-risk population.

Methods

Study selection process

The studies retrieved from the respective databases will be imported into Covidence software to streamline the management and organization of the screening process. Two reviewers will independently screen the titles and abstracts of all identified studies. Furthermore, the reviewers will independently evaluate the full texts based on the established eligibility criteria. Any disagreements will be resolved through consensus with the involvement of a third reviewer. The PRISMA 2020 flowchart of study selection is shown in Figure 1.

Figure 1. PRISMA 2020 flowchart of study selection.

Discussion

Individuals with visual impairments are often at a substantially higher risk of developing depression, with research showing that the prevalence of depressive symptoms is notably greater in this population in comparison to individuals without visual impairments. This heightened vulnerability may be attributed to various factors, including the challenges associated with daily functioning, social isolation, and the psychological impact of diminished independence.^18,19

Previous research has examined the presence of depressive symptoms in individuals with visual impairment. While some studies have specifically emphasized clinical eye examinations, others have used self-reported measures to assess visual impairment. Importantly, the prevalence of depression in this population has been investigated using various measures of depressive symptoms, resulting in differing findings across studies.^20–24

Furthermore, a previous systematic review included 10 studies conducted exclusively on elderly populations. However, due to the limitations of these reviews, a meta-analysis could not be conducted.²⁵ Previous systematic reviews and meta-analyses examined the prevalence of depression in individuals with visual impairment targeted community-dwelling adults,²⁶ while another focused on patients receiving care at eye clinics.²⁷

Moreover, no previous systematic review or meta-analysis has specifically investigated the incidence of depression in individuals with visual impairment, pointing to a significant gap in the literature. Thus, we identified an opportunity to undertake a systematic review and meta-analysis to evaluate the prevalence and incidence of depression in individuals with visual impairment. Our study intended to address the existing research gap by providing precise and reliable estimates of the pooled prevalence and incidence of depression within this specific population. Additionally, we aimed to assess the prevalence of depression among subgroups within the visual impairment population, considering factors such as study period, design, continent, income classification, study setting, age groups, methods of visual impairment assessment, severity of visual impairment, and tools used for depression assessment.

The strength of this review lies in its methodological rigor, incorporating subgroup analyses to elucidate variations in depression prevalence and identify critical determinants of mental health outcomes in individuals with visual impairment. The findings will contribute valuable insights to the field of public health and clinical practice by highlighting the burden of depression in this vulnerable population and informing targeted interventions, policies, and future research directions. Ultimately, this systematic review will enhance our understanding of the complex interplay between visual impairment and mental health, offering evidence-based guidance for healthcare providers, policymakers, and researchers to improve the psychological well-being of individuals living with visual impairment worldwide.

Author contributions

Tantirattanakulchai, Pankaew: Conceptualization, Data Curation, Investigation, Methodology, Project Administration, Visualization, Writing – Original Draft Preparation, Writing – Review & Editing

Hounnaklang, Nuchanad: Conceptualization, Funding Acquisition, Methodology, Supervision, Writing – Original Draft Preparation, Writing – Review & Editing

Win, Nanda: Conceptualization, Data Curation, Writing – Original Draft Preparation

Tepjan, Suchon: Conceptualization, Data Curation

Pongsachareonnont, Pear Ferreira: Conceptualization, Methodology