What are the benefits and risks of surgery for epiretinal membrane (a disease of the eye)?

Why is this question important?
An epiretinal membrane is an abnormal layer of tissue that develops at the back of the eye. It affects around one in five people aged 75 years and older. In most people, the development of an epiretinal membrane is linked to the normal ageing processes in the eye and is described as 'idiopathic'. In other instances, epiretinal membrane is caused by a pre-existing condition affecting the retina, such as inflammation or poor circluation. Epiretinal membrane can also develop after eye surgery.

Epiretinal membrane typically forms over the part of the eye responsible for seeing fine detail (the macula). In some people, this does not affect vision. In others, it causes distorted or blurred vision, which can affect people’s quality of life. For example, an epiretinal membrane may impair people’s ability to read or drive.

If an epiretinal membrane affects vision, it is commonly removed by surgery. A local anaesthetic (medication) is used to numb the eye area. As with any procedure, this surgery carries risks of harm from side effects. These include potential problems such as cataract, detached retina, infection and bleeding in the eye.

To understand when the benefits of surgery outweigh its risks, we reviewed the research evidence.

How did we identify and evaluate the evidence?
First, we searched the medical literature for studies:

- in which epiretinal membrane was not caused by a pre-existing condition or surgery;

- that compared the effects of surgery against no surgery or a placebo (sham) procedure; and

- where people were randomly assigned to one of two groups: a group that underwent surgery for epiretinal membrane, and a group that did not have surgery for epiretinal membrane.

We then summarised the evidence and rated our confidence in it, based on factors such as study methods and size.

What did we find?
We found only one study that met our criteria. This study took place in Denmark and included 53 people who had epiretinal membranes causing mild impairment of sight. Participants were randomly assigned to one of two groups. Those in one group had immediate surgery. Those in the other group were watched closely and in the event of any deterioration in their condition were invited to have surgery. People in both groups were followed up for one year.

The study results suggest that immediate surgery for epiretinal membrane causing mild impairment of sight:

- may not benefit vision 12 months after surgery; and

- may not lead to serious unwanted effects. One person treated with immediate surgery experienced an unwanted effect that was not considered serious. This was the development of an eye condition caused by fluid building up at the back of the eye.

The study did not investigate the impact of surgery on participants’ quality of life.

How confident are we in the evidence?
We are not confident in the evidence, because:

- it is based on one small study; and

- some of the methods used by the researchers who conducted it may have introduced errors in its results.

What does this mean?
For epiretinal membrane causing severe disabling impairment of sight, we found no carefully-controlled study that measured the effect of surgery. For severe epiretinal membrane, surgery is widely considered to improve the outcome and is routine practice. A carefully controlled trial comparing surgery to no treatment is considered unecessary and ethically inappropriate.

For epiretinal membrane causing mild impairment of sight, however, the effect of surgery is uncertain. There is some evidence that the outcome of watchful waiting may be as good as the effect of immediate surgery. However, the evidence is not strong enough to draw firm conclusions. Further studies that use robust methods and measure outcomes including quality of life in the longer term would help to determine effect of surgery with more confidence.

How up-to-date is this review?
The evidence in this Cochrane Review is current to May 2020.

Authors' conclusions: 

We found no RCT that directly investigated the effect of surgery compared to no intervention. For severe disabling epiretinal membrane, the lack of a RCT comparing surgery to no intervention may reflect evidence from non-randomised studies in favour of surgery; a RCT may be considered unnecessary and ethically unacceptable because a superior effect of surgery is widely accepted. For mild symptomatic epiretinal membrane, however, the value of surgery is uncertain. Low-certainty evidence from this review suggests that watchful waiting or deferred surgery may offer outcomes as favourable as immediate surgery. However, this finding needs to be confirmed in further RCTs with appropriate statistical power, masking of treatment allocation, consistent management of cataract, and measurement of outcomes including patient-reported quality of life over a more extended time frame.

Read the full abstract...
Background: 

Epiretinal membrane is an abnormal sheet of avascular fibrocellular tissue that develops on the inner surface of the retina. Epiretinal membrane can cause impairment of sight as a consequence of progressive distortion of retinal architecture.

Objectives: 

To determine the effects of surgery compared to no intervention for epiretinal membrane.

Search strategy: 

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE Ovid, Embase Ovid, ISRCTN registry, US National Institutes of Health Ongoing Trials Register ClinicalTrials.gov, and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP). There were no restrictions to language or year of publication. The databases were last searched on 20 May 2020.

Selection criteria: 

We included randomised controlled trials (RCTs) assessing surgical removal of idiopathic epiretinal membrane compared to placebo, no treatment or sham treatment. Paired or within-person studies were included, as well as those where both eyes of a single participant were treated.

Data collection and analysis: 

We used standard methods expected by Cochrane, and assessed certainty using the GRADE system. We considered the following five outcome measures: mean change in best corrected visual acuity (BCVA) in the study eye between baseline (before randomisation), 6 months and 12 months later; proportion of people with a gain of 0.3 logMAR or more of visual acuity in the study eye as measured by a logMAR chart at a starting distance of 4 m at 6 months and 12 months after randomisation; proportion of people with a loss of 0.3 logMAR or more of visual acuity in the study eye as measured by a logMAR chart at a starting distance of 4 m at 6 months and 12 months after randomisation; mean quality of life score at 6 months and 12 months following surgery, measured using a validated questionnaire; and any harm identified during follow-up.

Main results: 

We included one study in the review. This was a RCT including 53 eyes of 53 participants with mild symptomatic epiretinal membrane and BCVA of 65 or more Early Treatment Diabetic Retinopathy Study (ETDRS) letters. Participants were randomly allocated to immediate surgery or to watchful waiting with deferred surgery if indicated by evidence of disease progression. The study was limited by imprecision owing to the small number of participants and was at some risk of bias owing to inconsistencies in the time points for outcome assessment and in the management of lens opacity.

At 12 months, the visual acuity in the immediate surgery group was higher by a mean of 2.1 (95% confidence interval (CI) -2.0 to 6.2 ETDRS letters; 53 participants; low-certainty evidence) than the watchful waiting/deferred surgery group.

The evidence of the effect of immediate surgery on gains of 0.3 logMAR or more of visual acuity is very uncertain (risk ratio (RR) 0.55, 95% CI 0.06 to 4.93; 53 participants; very low-certainty evidence).

At 12 months, no participant in either group sustained a loss of 0.3 logMAR or more of visual acuity (53 participants; low-certainty evidence).

The included study did not measure quality of life.

At 12 months, no serious adverse event was identified in any participant. One participant developed chronic minimal cystoid macular oedema following immediate surgery (53 participants; low-certainty evidence).

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