What is an Epiretinal Membrane? (ERM)
An epiretinal membrane is a fibroglial collection of cells which have formed a layer over the retinal surface. Rather like a sheet of cellophane it can contract to scrunch up the underlying retina.
This causes light to unevenly fall on the retina and produces distortion and metamorphopsia in vision (lines on a grid may look curvy or rounded). Epiretinal membranes which have involved the macula are more noticeable as central vision is affected.
This results in distorted vision with both size and the shape of images being affected. It can make reading difficult, and can cause straight lines to be seen as wavy or the words distorted.
What Causes Epiretinal Membrane?
There are many causes of epiretinal membranes. Some are due to previous inflammation in the eye or as a result of a blocked retinal vein, or previous surgery or laser treatment.
A large proportion of epiretinal membranes are idiopathic in nature (they may arise spontaneously). It is more common to develop epiretinal membranes after the age of sixty when the vitreous has separated from the retinal surface leaving an exposed surface for the membrane to grow.