Screening to prevent damage to the optic nerve due to open angle glaucoma

Open angle glaucoma (OAG) is the commonest type of glaucoma in white European and African people and is the commonest cause of irreversible blindness. Its onset is insidious and progression symptomless until the condition is far advanced and central vision is lost. Because of this, OAG is assumed to be a condition which should be screened for, but good evidence to support this is lacking. Risk factors for developing OAG include increasing age, raised pressure inside the eye and a history in the family. It is more common in people with African origin, may come on at an early age and is more aggressive. The field of vision (side vision) is gradually lost but changes in the appearance of the optic nerve (where it appears inside the back of the eye) usually occur first. Raised pressure inside the eye may not be present and many with raised pressure do not have glaucoma. Tests for the disease are examination of the optic nerve, measurement of eye pressure and visual field assessment. The challenge of screening is to find people with the disease at a stage when the diagnosis is not in doubt and at risk of going blind if left untreated.

The aim of this review was to determine the impact of screening on the prevalence and severity of optic nerve damage due to OAG. We searched for randomised controlled trials (RCTs) of screening versus no screening for OAG because effectiveness of screening as a means of preventing the ill effects of a disease in a population can only be demonstrated by RCTs. We identified 1360 reports of studies but none were RCTs of screening. Therefore, there is insufficient evidence to recommend population based screening for OAG. However much can be done to improve awareness of the condition and encourage those at higher risk to seek testing. In wealthy countries where there is access to high quality eye care and good health education, blindness from OAG should become increasingly rare. Much greater challenges face poor and emerging economies and countries where there is not equal access to good healthcare. The potential effectiveness of screening for OAG in preventing optic nerve damage and ultimately preventing blindness should be tested by high quality RCTs of screening.

Authors' conclusions: 

On the basis of current evidence, population-based screening for chronic OAG cannot be recommended, although much can be done to improve awareness and encourage at risk individuals to seek testing. In wealthy countries with equitable access to high quality eye care and health education, blindness from chronic OAG should become increasingly rare; much greater challenges face poor and emerging economies and countries where there are substantial health and wealth inequalities. Effectiveness of screening for OAG can be established only by high quality RCTs.

Read the full abstract...

Open angle glaucoma (OAG) is a primary, progressive optic neuropathy; the onset is without symptoms and progression occurs silently until the advanced stages of the disease, when it affects central vision. The blindness caused by OAG is irreversible. It has often been assumed to be a condition that fulfils the criteria for population screening, although this has not been supported by other in-depth non-systematic reviews. The focus of this review was to examine the evidence for the effectiveness of screening for OAG.


To determine the impact of screening for OAG compared with opportunistic case findings or current referral practices on the prevalence of and the degree of optic nerve damage due to OAG in screened and unscreened populations.

Search strategy: 

We included any randomised controlled trial (RCT) evaluating population-based screening programmes for OAG with a minimum one year follow up. We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library, Issue 4, 2008), MEDLINE (January 1950 to January 2009), EMBASE (January 1980 to January 2009), the UK Clinical Trials Gateway (UKCTG) and ZETOC (January 1993 to January 2009). There were no language or date restrictions in the search for trials. The electronic databases were last searched on 12 January 2009.

Selection criteria: 

We planned to include RCTs, including cluster RCTs.

Data collection and analysis: 

Two review authors independently assessed the study abstracts identified by the electronic searches. We did not find any trials that met the inclusion criteria.

Main results: 

As no trials were identified, no formal analysis was performed.