Choosing appropriate patient-reported outcome instruments for glaucoma research: a systematic review of vision instruments

Methodological quality of the review: Medium confidence

Author: Che Hamzah J, Burr JM, Ramsay CR, Azuara-Blanco A, Prior M

Geographical coverage: Not reported

Sector: Glaucoma

Sub-sector: Patient-reported outcome instruments, validity

Equity focus: None specified

Review type: Effectiveness review

Quantitative synthesis method: Narrative analysis

Qualitative synthesis method: Not applicable

Background: Traditionally, evaluation of outcomes in glaucoma clinical trials has focused on clinical measures of glaucoma status, mainly the extent of visual field loss and level of intra-ocular pressure (IOP). However, such measures do not capture any effects of glaucoma or its treatment on activity limitation and overall wellbeing.

Patient-reported outcomes (PRO) are defined as “outcomes reported by patients”. Aspects covered include patients’ physical ability to carry out activities of daily living (such as self-care and walking), psychological (emotional and mental wellbeing), social functioning (relationships with others, participation in social activities), perception of health status, personal construct and satisfaction with life and care.

PROs of visual functioning and quality of life (QOL) are important as the ultimate goal of therapy is to maintain patients’ ability to function in everyday life. They should not be considered as surrogates for objective measures of disease as they are measuring different constructs. A large number of instruments have been developed to measure PROs. Selecting an instrument depends on the objectives of the study and the target population.

Objectives: To identify patient-reported outcome instruments relevant to glaucoma and assess their content validity.

Main findings: A total of 33 vision-specific PRO instruments were included in the review. 16 instruments were vision-specific, 16 were glaucoma-specific and one combined instrument was identified. 13 vision-specific instruments comprised instruments measuring vision status, two looked at vision disability, and one looked at vision satisfaction.

Of the glaucoma-specific instruments, five measured glaucoma status, one measured glaucoma medication related to health status, four looked at glaucoma medication impairment, and six measured glaucoma medication satisfaction. The National Eye Institute Visual Function Questionnaire-25 “Impact of Vision Impairment and Treatment Satisfaction Survey-Intraocular Pressure” had the highest number of positive ratings in the content validity assessment.

Authors note that this systematic review provides a descriptive catalogue of vision-specific PRO instruments, to inform the choice of an appropriate measure of patient-reported outcomes in a glaucoma context.

Methodology: All articles, published in English, reporting the use of vision PRO instruments in adult glaucoma participants were included. Once an instrument was identified, any article related to its development, and/or validation of the instruments ascertaining to the final version of the instrument, was also included. The content of each instrument had to be fully described in the articles and freely available. Reviews, letters and editorials were excluded. Authors searched the following databases: MEDLINE and MEDLINE In process, EMBASE and SCOPUS.

Two reviewers independently screened the titles and abstracts of all articles identified by the search strategy, assessed articles against the inclusion criteria and identified vision PRO instruments from primary studies for inclusion. For each instrument, two reviewers independently extracted data. A data extraction form was developed and piloted on four instruments selected from those identified and refined accordingly.

Two reviewers independently assessed the quality of included instruments using a modified version of the published quality-assessment tool. Each criterion was evaluated with a positive rating, a minimal acceptable rating, or a negative rating. A “higher quality” study was considered to be one with a high number of positive ratings.

Data synthesis consisted of a review of vision instruments. These were categorised into vision-specific, glaucoma-specific and combined instruments.

Applicability/external validity: Authors did not discuss the generalizability of the results.

Geographic focus: Geographical focus of studies and/or instruments were not reported in the review.

Summary of quality assessment: Medium confidence was attributed in the conclusions about the effects of this study. Authors used appropriate methods to select and extract data and quality-assess studies included in the review. To facilitate content validity in this review, an attempt was made to categorise instruments by mapping the instruments’ content to the WHO ICF framework, and analyse findings from this review in a narrative manner. Authors also acknowledged potential limitations of this review. However, search strategy consisted of database search and searching unpublished studies; references of included studies and contacting authors/experts were not part of the search strategy. This indicates the presence of publication bias. Additionally, authors included studies written in English only, implying language bias.