This is a protocol for a Cochrane Review (prognosis). The objectives are as follows:

Primary objective

To identify prognostic risk factors for progression of functional visual outcomes of primary open angle glaucoma (POAG) and pseudoexfoliation glaucoma (PXFG) in adults.

Table 1. PICOTS of the primary objective

Population

Adults ≥ 18 years of age of any ethnicity with open angle glaucoma (restricted to POAG and PXFG types) diagnosed as having open angle and evidence of glaucomatous damage. We will exclude studies evaluating risk factors on those who have already undergone surgical treatment for glaucoma.

Index prognostic factors

Prognostic factors associated with the progression of open angle glaucoma (restricted to POAG and PXFG types), evaluated in primary studies.

 

Specific prognostic factors of interest will include, but are not restricted to: patient demographic information, such as age, sex, ethnicity, and socio-economic status; clinical data, such as comorbidities (presence or absence of cardiovascular disease, diabetes, hypothyroidism, obstructive sleep apnoea, etc.) and variations in systemic blood pressure (diastolic blood pressure, systolic blood pressure, mean arterial pressure); and functional and structural biomarkers in the prognostic context of the POAG or PXFG. We will also consider the stage of glaucoma at baseline (mild, moderate, severe types). We expect that prognostic factors will generally be measured at the time that participants enter the study, and after the diagnosis of POAG or PXFG has been made.

Comparator

Not applicable

Outcomes

Primary outcome: progression of glaucoma that has been ascertained by visual fields (VF) (functional assessment), or by VF plus imaging test (e.g. OCT) will be the main outcome of interest for the primary objective.

We will exclude studies that have assessed structural outcomes using optical coherence tomography (OCT) only.

Timing

We will include studies that present the above outcome with at least 2 years follow-up after diagnosis. Ideally, the period of follow-up should be 5 years or more. 

Setting

We will include studies undertaken in any care setting, with no geographical limitations.

Secondary objectives

To identify prognostic risk factors for progression of structural outcomes of POAG and PXFG in adults.

Table 2. PICOTS of the secondary objective

Population

Adults ≥ 18 years of age of any ethnicity with open angle glaucoma (restricted to POAG and PXFG types) diagnosed as having open angle and evidence of glaucomatous damage. We will exclude studies evaluating risk factors on those who have already undergone surgical treatment for glaucoma.

Index prognostic factors

We anticipate that there will be fewer studies that have assessed glaucoma progression using OCT. However, the prognostic factors that we will consider and expect to be measured in the included studies are similar to those for the primary objective.

Comparator

Not applicable

Outcomes

Progression of glaucoma that has been ascertained by OCT or any other imaging test (structural assessments) will be the outcome of interest for the secondary objective.

Timing

We will include studies that present the above outcome with at least 2 years follow-up after diagnosis. Ideally, the period of follow-up should be 5 years or more. 

Setting

Studies undertaken in any care setting, with no geographical limitations.

Investigation of sources of heterogeneity between studies

We anticipate between-study heterogeneity relating to two key areas in this review:

Clinical heterogeneity including characteristics of the participants such as ethnicity/race; primary interventions such as medical treatment, or laser treatment, or both for POAG or PXFG; concurrent interventions such as phacoemulsification +/- intraocular implantation in study cohorts.

Methodological heterogeneity generated from different study designs and how robustly studies are conducted and their approach to analysis.

We will visually explore these potential sources of heterogeneity by grouping studies on forest plots. If a meta-analysis is possible and sufficient data are available, we will further investigate using subgroup analyses or meta-regression.