Barriers and Enablers to Medication Adherence &amp; Compliance in Glaucoma – A Scoping Review Protocol

Áine Kelly; Chríosa O'Connor; Pauline Goulding; Jeremy O'Connor; Rory Murphy; Colm O'Brien; Deborah Wallace

doi:10.12688/hrbopenres.14405.1

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Study Protocol

Barriers and Enablers to Medication Adherence & Compliance in Glaucoma – A Scoping Review Protocol

[version 1; peer review: 1 approved with reservations]

Áine Kelly ¹, Chríosa O'Connor², Pauline Goulding², [...] Jeremy O'Connor³, Rory Murphy³, Colm O'Brien^1,2, Deborah Wallace¹

Áine Kelly ¹, Chríosa O'Connor², [...] Pauline Goulding², Jeremy O'Connor³, Rory Murphy³, Colm O'Brien^1,2, Deborah Wallace¹

PUBLISHED 16 Apr 2026

Author details Author details

¹ Clinical Research Centre, University College Dublin School of Medicine, Dublin, Leinster, Ireland
² Department of Ophthalmology, Mater Misericordiae University Hospital, Dublin, Leinster, Ireland
³ Department of Ophthalmology, Royal Victoria Eye and Ear Hospital, Dublin, Leinster, Ireland

Áine Kelly
Roles: Conceptualization, Investigation, Methodology, Project Administration, Visualization, Writing – Original Draft Preparation, Writing – Review & Editing

Chríosa O'Connor
Roles: Funding Acquisition, Project Administration, Writing – Review & Editing

Pauline Goulding
Roles: Funding Acquisition, Project Administration, Writing – Review & Editing

Jeremy O'Connor
Roles: Funding Acquisition, Project Administration, Writing – Review & Editing

Rory Murphy
Roles: Funding Acquisition, Project Administration, Writing – Review & Editing

Colm O'Brien
Roles: Conceptualization, Funding Acquisition, Investigation, Methodology, Project Administration, Supervision, Writing – Review & Editing

Deborah Wallace
Roles: Conceptualization, Funding Acquisition, Investigation, Methodology, Project Administration, Supervision, Validation, Writing – Original Draft Preparation, Writing – Review & Editing

OPEN PEER REVIEW

REVIEWER STATUS

Abstract

Background

Glaucoma is the leading cause of irreversible blindness worldwide with increased intraocular pressure (IOP) being the primary modifiable risk factor. It is often referred to as the “silent thief of sight” for its progressive, mostly asymptomatic disease course until advanced stages. First line treatment is to lower IOP by topical medication. However, adherence with topical medication is problematic, with approximately 50% of patients taking their glaucoma medication one year post diagnosis. It is essential that patients commencing treatment are adherent since suboptimal adherence is reportedly related to poor clinical, social and economic outcomes. The aim of this review is to better understand the influential factors (barriers and enablers) to adherence and the attempted interventions to improve adherence rates.

Methods

This scoping review will include searches in EMBASE, Medline, Psych Info, CINAHL and Web of Science electronic databases. Primary research studies and peer-reviewed grey literature will be eligible for inclusion. Studies not fully available in English will be excluded. Titles and abstracts will be screened for inclusion and full text screening of articles will be carried out independently by two reviewers. A data extraction framework will guide the literature screening. A qualitative data analysis will be carried out to assess relevant literature and data will be presented in a narrative synthesis format. Quality appraisal of the included studies will not be performed.

Discussion

These findings will advance our understanding of barriers and enablers to medication adherence in glaucoma. Findings will be relevant to patients, clinicians and stakeholders in the glaucoma care pathway. Evidence synthesised will also help inform the development of an educational tool to improve adherence as part of the overall project.

Keywords

Glaucoma, medication adherence, compliance, enablers, barriers, intervention, education

Corresponding author: Áine Kelly

Competing interests: No competing interests were disclosed.

Grant information: This research is funded by a UCD Health Affairs Academic Health Science System Grant (2025). The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.
The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Copyright: © 2026 Kelly Á et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

How to cite: Kelly Á, O'Connor C, Goulding P et al. Barriers and Enablers to Medication Adherence & Compliance in Glaucoma – A Scoping Review Protocol [version 1; peer review: 1 approved with reservations]. HRB Open Res 2026, 9:36 (https://doi.org/10.12688/hrbopenres.14405.1) First published: 16 Apr 2026, 9:36 (https://doi.org/10.12688/hrbopenres.14405.1) Latest published: 16 Apr 2026, 9:36 (https://doi.org/10.12688/hrbopenres.14405.1)

Introduction

Non-adherence to medical therapies is a global health concern with the World Health Organisation (WHO) estimating that within developed countries, only 50% of people with chronic conditions regularly take their medical therapies.¹ Glaucoma, a chronic, progressive optic neuropathy, is the leading cause of irreversible blindness worldwide.² In 2020, glaucoma was the second most common cause of global blindness and is predicted to increase in prevalence to 111.8 million by 2040.³ With increased intraocular pressure (IOP) being the primary modifiable risk factor,⁴ lowering IOP using topical ophthalmic medications is a crucial pillar in management of disease, and adherence is key to a successful treatment program. Glaucoma is a progressive, mostly asymptomatic disease course until the advanced stages⁵ therefore, adherence can be problematic with approximately only 50% of patients taking their glaucoma medications one year post diagnosis.⁶ With an ageing global population at increased risk of developing glaucoma, it is imperative that those commencing topical medication treatment are adherent since suboptimal adherence is related to poor clinical, social and economic outcomes. It is equally important that all stakeholders, both patients and healthcare professionals understand the factors influencing adherence in order to provide more tailored strategies and support.

Adherence and compliance are often used interchangeably but are defined differently. Adherence is ‘the extent to which a person’s behaviour, taking medication, following a diet or executing lifestyle changes, corresponds with agreed recommendations from a healthcare professional’. It is a positive, pro-active lifestyle change. Whereas, compliance is ‘the extent to which a patient’s behaviour matches the prescribers recommendations’.⁷ It is a measure of their following of instructions by healthcare professionals. For the purpose of this manuscript we shall use adherence, however, in order to maximise our search and capture as broad a range of relevant papers as possible, we will include both compliance and adherence in our keywords and search string.

Reported barriers to adherence are multifactorial. Patient-related barriers include; forgetting to take drops, physical difficulty administering drops, lack of understanding of the disease, or low motivation when symptoms are not yet significant.⁸ Medication-related factors such as multiple-drop regimens or side-effects secondary to medication toxicity add further challenges to adherence,⁹ while system-related barriers include inadequate communication, lack of follow-up or cost.¹⁰ Conversely, enablers such as good clinician–patient rapport, simplified dosing, effective education, and reminder tools can foster adherence.^11,12 Little is known about the treatment for poor adherence. Interventions that have been explored include printed educational materials, such as the Support, Educate, Empower (SEE) programme,¹³ pharmacist-led counselling,¹⁴ text message reminders and mobile-app monitoring.¹⁵ However, their effectiveness and reproducibility remain unclear.

Aims and objectives

The aim of this scoping review is to enhance our understanding of the barriers and enablers to glaucoma medication adherence as well as examining the interventions trialled to improve rates of adherence. Evidence synthesised will also help inform the development of an educational tool to improve adherence as part of the overall project.

Methods

A scoping review will be conducted according to the methodology laid out by the Joanna Briggs Institute,¹⁶ incorporating the framework proposed by Arksey and O’Malley.¹⁷ This framework consists of five steps, namely identifying the main research question, identifying the relevant studies, the conducting of study screening, data charting and finally analysing data collected and reporting results.

This review will systematically follow the standards as outlined by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR).¹⁸ This checklist incorporates 20 items that must be included when carrying out a review and two items to include in addition to the core 20 specifically tailored to a scoping review. Any significant protocol amendments will be updated on the HRB Open Research site.

Research question

A three step search strategy was used, whereby a preliminary search was carried out of two databases and keywords identified. This was conducted in order to identify the main types of available literature, current knowledge gaps that exist, clarify the aims of the review and identify key concepts and definitions. This was combined with the population, concept, context (PCC) framework as designed by Peters et al.,.¹⁶ The PCC framework is a tool recommended for scoping reviews by the Joanna Brigg’s Institute and commonly used in quantitative research. It helps to inform the research question design, inclusion criteria and search strategies for scoping reviews. It is related somewhat to the PICO (Population, Intervention, Comparator and Outcome) mnemonic commonly used in systematic reviews, but allows for broader topic mapping and is outlined below.

This scoping review has been designed to answer the following research question:

What barriers or enablers have been identified in influencing patients’ adherence or compliance with glaucoma medication and what educational resources and interventions exist or have been trialled to improve this?

Population: Adults (≥18 years) with a diagnosis of any glaucoma subtype who are prescribed one or more topical intraocular pressure lowering medications.

Concept: Barriers and enablers to medication adherence or compliance; any interventions (educational, psychological, behavioural, technological, or system-based) designed to address these factors; reported efficacy and trial duration.

Context: Global scope—no restriction by geography, healthcare system, or publication language (subject to English accessibility).

Eligibility criteria

Inclusion criteria

• Peer-reviewed primary research articles.
• Peer-reviewed grey literature sources.
• Patients (male and female) ≥ 18 years with a diagnosis of glaucoma.
• Studies identifying barriers and or enablers to glaucoma medication compliance or adherence.
• Studies discussing any intervention to attempt to improve glaucoma medication compliance or adherence.
• Studies from any geographical location and any timeframe to improve the scope of the review and help remove bias.
• Studies from both private and public sectors.

Exclusion criteria

• Studies in paediatric glaucoma populations.
• Non-peer reviewed primary research studies and grey literature.
• Studies where the topic is glaucoma medication but no reference to adherence, compliance or intervention is made.
• Studies limited to surgical/laser treatment adherence.
• Studies not fully available in English as translation facilities are unavailable.

Search strategy

Keywords and index terms were identified in the preliminary search, gathered and discussed with an academic librarian at University College Dublin. Five electronic databases were chosen for inclusion in the search; EMBASE, Psych Info, Medline, CINAHL and Web of Science. Grey literature will be searched by reviewing ProQuest. In addition, literature that discusses any intervention of any category that has aimed to improve glaucoma medication adherence will be identified. A search strategy was developed using controlled vocabulary to include MeSH and free-text terms. As referenced above, the PRISMA-ScR checklist will be used. A sample of the search string for PubMed to include Boolean terms is shown below,

((((glaucoma) OR (glaucoma [MeSH Terms])) OR (glaucoma [Title/Abstract])) AND (((((((((((ophthalmic solution [MeSH Terms])) OR (ophthalmic solutions [MeSH Terms])) OR (ocular hypotensives [Title/Abstract])) OR (glaucoma medication [Title/Abstract])) OR (ophthalmic solutions [Title/Abstract])) OR (topical glaucoma therapy [Title/Abstract])) OR (topical glaucoma therapy)) OR (ocular hypotensive)) OR (ophthalmic solution*)) OR (glaucoma medication))) AND ((((((((((adherence) OR (medication adherence)) OR (treatment adherence and compliance)) OR (persistence)) OR (tolerability)) OR (adherence, treatment [MeSH Terms])) OR (compliance, treatment [MeSH Terms])) OR (treatment adherence and compliance [MeSH Terms])) AND (((((((barriers) OR (enablers)) OR (facilitators)) OR (factor, enabling [MeSH Terms])) OR (barriers [Title/Abstract])) OR (enabl*[Title/Abstract])) OR (facilitat*[Title/Abstract]))) OR (((((((((adherence) OR (medication adherence)) OR (treatment adherence and compliance)) OR (persistence)) OR (tolerability)) OR (adherence, treatment [MeSH Terms])) OR (compliance, treatment [MeSH Terms])) OR (treatment adherence and compliance [MeSH Terms])) AND ((((((((((intervention) OR (education*)) OR (adherence intervention [MeSH Terms])) OR (adherence enhancing intervention*[MeSH Terms])) OR (adherence improving intervention [MeSH Terms])) OR (education [MeSH Terms])) OR (activity, educational [MeSH Terms])) OR (adherence, guideline [MeSH Terms])) OR (intervention*[Title/Abstract])) OR (education*[Title/Abstract])) OR (trial*[Title/Abstract]))))

Screening and study selection

Covidence software¹⁹ will be used for screening purposes. Duplicates will be removed prior to screening. Reviewer one (AK) and reviewer two (RL) will screen the titles, abstracts and keywords of the identified studies to assess eligibility for inclusion based on the criteria outlined. Following identification of potentially relevant studies full text screening will occur, followed by screening of references. Full text screening will be completed by reviewer one (AK) and two (RL). Any discrepancies will be resolved by a third reviewer (DW). Authors may be contacted if additional information is required. Reasons for exclusion of articles for full text screening will be provided. The search strategy and selection process for the studies will be outlined in accordance with PRISMA-ScR¹⁸ and a PRISMA flow diagram will be used to summarise and display the study selection.

Data extraction

Reviewer one (AK) will use a data extraction form to extract the relevant data from the included studies. A data extraction framework will guide the literature screening ( Table 1). A data extraction form will be developed and a pilot data extraction review will be performed. The data extraction form will be dynamic until this point where data points may be included or excluded in addition to the extraction form. A random sample (10%) of data extracted will be verified by reviewer two (RL).

Table 1. Data categories to be identified and extracted.

Data category	Items extracted
Citation	Author(s), year, title, journal, volume, pages
Country/setting	Location, healthcare system (if specified)
Population	Participant number, age/sex distribution, glaucoma type, number of drops prescribed, types of drops prescribed
Adherence or Compliance measure	Method used (self-report, electronic monitoring, prescription refill, etc.)
Barriers identified	Any factor influencing suboptimal adherence
Enablers identified	Any factor improving adherence or persistence
Intervention type	Educational, behavioural, technological, psychological, supportive
Intervention details	Description, delivery mode, duration, follow-up length
Outcomes	Adherence/compliance rate, patient satisfaction, knowledge gain, IOP outcomes
Reported efficacy	Qualitative summary or quantitative result
Notes	Reviewers’ conclusions, implications for practice

Risk of bias assessment

Not applicable for this review.

Data synthesis

A narrative synthesis approach will be employed by reviewer one (AK) to analyse the data.²⁰ Data will be summarised both descriptively and thematically, will follow PRISMA-ScR guidelines and be grouped using the domains of the PCC framework. The research questions will be reported on separately and data will be presented narratively in charts and tabular form. Studies will be categorised by year, country, design, population, and intervention type. Frequency graphs and tables will summarise distribution and trends. Barriers and enablers will be divided into patient-related, medication-related, provider-related and system-related categories. Interventions will be grouped by type, including educational, behavioural, technological or multi-component variations. Where reported, efficacy and duration of follow-up will be tabled to attempt to identify trends in successful interventions. A qualitative data analysis will be carried out to assess relevant literature.

Ethics and dissemination

Ethical approval was not required for the publication of this scoping review, as it involves material available to the public. The scoping review will be published in a peer review journal in order to contribute to the existing body of literature. The results of this review will be presented at national and international Ophthalmic conferences.

Protocol registration

This protocol has been registered on Open Science Framework (https://osf.io/), an accessible open-source software repository for researchers that aids in open collaboration. The protocol can be located at the following link: https://osf.io/6bd8a/overview; https://osf.io/cq7pb/overview Barrier and Enablers to Medication Adherence & Compliance in Glaucoma – A Scoping Review Protocol. Registration DOI 10.17605/OSF.IO/6BD8A

Discussion

Adherence to glaucoma medication is a pillar of disease management but adherence is often poor. This problem is multifactorial, not least owing to its insidious onset and often asymptomatic nature at time of diagnosis.²¹ This scoping review will facilitate a better understanding of the influential factors (barriers and enablers) to adherence by synthesising the diverse literature and elucidating the various components of glaucoma medication adherence.

Understanding why patients fail to adhere is of great importance prior to determining how to improve it.²² Evidence suggests that practical obstacles such as poor drop-instillation technique or forgetfulness often coexist with psychological barriers such as denial or lack of perceived benefit.²³ Educational and behavioural interventions can help alleviate these, but the long-term benefits of these interventions are uncertain. Several small studies demonstrate that targeted education or digital reminders can yield short-term adherence gains,²⁴ however, long-term persistence is rarely reported. This scoping review aims to synthesise the literature to investigate these issues.

While technological enablers, such as drop-reminders to target the patient-level barrier of forgetfulness are common,²⁵ fewer interventions target provider-level barriers such as health-system communication or the medication-level barrier such as need for dexterity for drop installation. Given a global ageing population and healthcare resource constraints, improving adherence through education could yield substantial clinical and economic benefits. We believe this review will provide important knowledge of the barriers and enablers to glaucoma medication adherence and summarise interventions which attempt to combat these issues. Findings from this review will impact both patients and stakeholders in the glaucoma care pathway and will help inform the development of an educational intervention to improve glaucoma medication adherence as part of an ongoing project.

Corresponding author: Áine Kelly ([email protected]).

ORCID iD

Áine Kelly https://orcid.org/0000-0002-0985-047X

Deborah Wallace https://orcid.org/0000-0003-2363-106X

Data availability statement

No data is associated with this article. Likewise, a dataset is not associated with this article as it is a protocol for a scoping review.

Acknowledgments

We would like to acknowledge the invaluable contribution of UCD academic librarian, Mr Diarmuid Stokes, for his assistance developing our search strategy.

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