An epiretinal membrane (ERM) is a thin sheet of scar-like material that grows on the surface of the macula, the central, most sensitive part of the retina. The membrane contracts and scrunches up the macula, wrinkling it and making it thicker, reducing the quality and/or quantity of vision. The wrinkling of the retina results in twisted or distorted vision. For example, straight lines may look wavy or have a kink in them; some people notice that letters look jumbled up when trying to read. This tends to happen early in the development of epiretinal membranes and may be the only symptom for many patients.
The thickening of the central part of the macula also causes blurring. This may happen with or without distorted vision, especially later in the development of the epiretinal membrane.
A vitrectomy operation is the only treatment available and is highly successful; 80-90% of patients find their distortion (quality of vision) improves and 70-80% see better centrally (quantity of vision). Symptoms generally worsen over months and may stabilise, but delaying treatment may mean results are not quite as good as with early surgery. Only 1 out of every 40 patients improves without surgery.
What Happens If An Operation Is Not Done?
Epiretinal membranes often worsen before stabilizing. The vision may worsen in line with the physical changes and remain stable long term. However, in others, even though the epiretinal membrane remains physically stable, the vision may get worse as the distorted macula slowly loses the ability to work as well. Importantly, this tends to be slow and epiretinal membrane is not a blinding condition.
When Should Surgery Be Done?
The longer an epiretinal membrane has been present, the lower the chance of the operation improving vision and the less any improvement in vision is likely to be. It is not, however, an emergency and vitrectomy surgery can usually wait for a while without making a significant difference to the outcome.
How Bad Does The Vision Need To Be Before Surgery Is Recommended?
Rather than simply using a vision chart cut-off in order to decide whether surgery is worthwhile, Dr Chauhan prefers to take the patient’s specific symptoms and visual requirements into account before recommending surgery. Specifically, he places greater emphasis on the degree to which patients are bothered and affected by distortion and blurring in their day-to-day lives than their vision on the chart. After all, daily life doesn’t consist of looking at bold black letters on a white background, but is much more subtle and complex.
It is often a good idea, if patients are uncertain and there is either very good visual acuity or no definite history of progression, to arrange a review appointment for 3 to 4 months later to reassess the epiretinal membrane as well as its impact on daily vision. An earlier appointment can always be rearranged if patients make an earlier decision.