How do different lighting conditions affect the vision and quality of life of people with glaucoma? A systematic review

Author: Enoch J, Jones L, Taylor DJ, Bronze C, Kirwan JF, Jones PR, Crabb DP.

Geographical coverage: Not reported

Sector: Glaucoma

Sub-sector: Screening, diagnosis

Equity focus:  Not reported

Study population: Patients with glaucoma

Review type: Effectiveness review

Quantitative synthesis method: Narrative synthesis

Qualitative synthesis method: Not applicable

Background:

Glaucoma is a group of diseases that damage the optic nerve and visual field (VF). It is a leading cause of blindness worldwide, with an estimated prevalence of approximately 3.5% in individuals aged 40 and older. Of these cases, 74% are attributed to primary open-angle glaucoma (POAG), which was projected to affect 53 million people globally by 2020. POAG is a progressive condition that often remains asymptomatic until substantial vision loss occurs, making it difficult to diagnose. Consequently, an estimated 50% of cases go undetected. However, early detection and treatment can preserve vision, highlighting the need to understand functional changes in early POAG to improve awareness and facilitate timely diagnosis. Some studies suggest that individuals with early-stage POAG may experience visual difficulties under non-standard lighting conditions, which may facilitate earlier diagnosis.

Objectives:

To systematically review evidence on the impact of different light levels on visual function and vision-related quality of life (QoL) in individuals with glaucoma.

Main findings:

Overall, the review highlighted that different lighting conditions, including low luminance, glare, and rapid transitions, significantly impair vision and quality of life for individuals with glaucoma. This underscores the importance of targeted interventions and adaptive strategies. The search identified 21,009 articles, of which 56 peer-reviewed studies published in English were included in this review. Of these, 54 were quantitative and two were qualitative. The majority of included studies were case-control (48%) and cross-sectional (41%), with the remainder comprising other study designs. The studies examined the impact of lighting on various aspects of life and vision in individuals with POAG, with 18 studies addressing quality of life, 16 focusing on psychophysical measures, 10 assessing functional vision, 10 exploring activities of daily living, and two offering qualitative insights.

POAG significantly impairs contrast sensitivity under low luminance, exacerbates glare sensitivity, and prolongs dark adaptation. These issues are more frequently reported in vision-related QoL assessments than in other domains and tend to worsen with increasing visual field loss. Notably, individuals with early-stage POAG face marked difficulties in low-light or fluctuating lighting conditions compared to age-matched controls, challenging the notion that early-stage POAG is asymptomatic. However, performance-based studies rarely detect significant differences between individuals with POAG and age-matched controls in simulated daily tasks under suboptimal lighting. Larger studies are needed to develop optimised ambient and task-specific lighting strategies to better support individuals with POAG.

Methodology:

Searches were conducted in Medline, Embase, CINAHL, PsycARTICLES, PsycINFO, and the Ovid Nursing Database to identify studies involving individuals with glaucoma, with a focus on those with chronic POAG. Studies were included if they were published in English, French, or Spanish, and reported on the impact of different lighting conditions on vision and vision-related QoL. Prospective and retrospective citation tracking was performed using Scopus and Google Scholar to identify additional relevant publications. Two reviewers independently screened the identified studies to assess eligibility, with discrepancies resolved through discussion or consultation with a third reviewer. Relevant data were extracted into a standardised table, and the methodological quality of the included studies was assessed using the Standard Quality Assessment Criteria for Evaluating Primary Research Papers from a Variety of Fields. The findings were synthesised narratively.

Applicability/external validity:

The review addressed applicability and external validity by emphasising the need for larger sample sizes and more robust performance-based studies to confirm findings. It noted that many studies had small sample sizes, employed varied methodologies, and did not consistently consider factors such as the location of visual field loss or co-existing conditions like cataracts. Additionally, many studies were conducted in controlled environments, which may limit their generalisability to real-world contexts. These limitations underscore the need for further research, particularly in naturalistic settings and with broader linguistic and methodological inclusivity, to enhance external validity and practical relevance.

Geographic focus: Not reported.

Summary of quality assessment:

There is low confidence in the conclusions of this review. The authors did not contact original investigators or experts, did not list excluded studies, did not specify the number of reviewers involved in data extraction, and did not categorise findings by risk of bias.