An epiretinal membrane forms when a thin layer of scar-like tissue grows across the surface of the retina, the light-sensitive tissue at the back of the eye. In most cases, the trigger is a normal age-related change inside the eye: the gel that fills the eyeball gradually pulls away from the retina, and this process sets off a chain of cellular activity that produces the membrane. Less commonly, eye injuries, surgeries, or other retinal diseases are responsible.
How the Vitreous Gel Triggers Membrane Growth
Your eye is filled with a clear, jelly-like substance called the vitreous. As you age, this gel slowly shrinks and eventually separates from the retina’s surface, a process called posterior vitreous detachment (PVD). PVD is extremely common after age 60 and is usually harmless. But the way the gel peels away can sometimes leave behind the conditions for an epiretinal membrane to form.
One mechanism involves cells called hyalocytes that normally sit at the boundary between the vitreous gel and the retina. When the vitreous separates, it can split in a way that leaves these hyalocytes behind on the retinal surface. Once stranded there, they become active: stimulating other cells to migrate from the bloodstream and the retina itself, promoting cell multiplication, releasing growth factors that encourage connective tissue production, and causing that new tissue to contract. The result is a thickened, sometimes wrinkled sheet of tissue sitting on top of the macula, the central part of the retina responsible for sharp vision.
A second mechanism involves the inner limiting membrane, the thin natural barrier on the retina’s inner surface. During vitreous separation, brief tugging on the retina can create tiny breaks in this barrier. Those openings allow cells of glial origin (the retina’s support cells) to escape onto the surface and begin proliferating, eventually forming a membrane.
What the Membrane Is Made Of
An epiretinal membrane is not a single cell type. It contains a mix of cells from both inside the retina and outside it: Müller glial cells (the retina’s main structural support cells), astrocytes, retinal pigment epithelium cells, hyalocytes from the vitreous, fibroblasts, and myofibroblasts. The myofibroblasts are particularly important because they can contract, which is what causes the membrane to tighten and wrinkle the retina underneath it. Several of the other cell types, including Müller cells, hyalocytes, and retinal pigment epithelium cells, can transform into myofibroblasts over time, which is why some membranes that start out thin and harmless eventually become contractile.
Idiopathic ERM: When There’s No Obvious Cause
The majority of epiretinal membranes are classified as idiopathic, meaning they develop without any underlying eye disease. The primary risk factor is simply age. Posterior vitreous detachment happens to most people eventually, and when it does, the biological conditions for membrane formation fall into place. Not everyone who experiences vitreous detachment will develop an epiretinal membrane, but the correlation is strong enough that increasing age remains the single biggest predictor.
If you already have an epiretinal membrane in one eye, there is a meaningful chance of developing one in the other eye as well. Data from the Blue Mountains Eye Study found that 13.5% of people with a membrane in one eye developed one in their second eye within five years.
Secondary Causes: Other Eye Conditions
When an epiretinal membrane develops alongside or because of another eye problem, it is considered secondary. The list of known triggers is broad:
- Diabetic retinopathy, where damaged blood vessels in the retina create an inflammatory environment that promotes abnormal tissue growth
- Retinal vein occlusion, a blockage in the veins draining the retina
- Retinal tears or detachment, which disrupt the retinal surface and expose underlying cells
- Chronic inflammation inside the eye (uveitis), which stimulates scar tissue formation
- Eye trauma, including blunt injuries
- Prior laser treatment to the retina
- Intraocular tumors
In all of these cases, the common thread is disruption or inflammation at the retinal surface, giving cells the opportunity and stimulus to migrate and proliferate where they normally would not.
Cataract Surgery and Membrane Formation
Cataract surgery deserves its own mention because it is one of the most common eye surgeries worldwide, and the link to epiretinal membrane development is well documented. In a large study tracking patients after uncomplicated cataract surgery, epiretinal membrane prevalence jumped from 3.1% before surgery to 14.8% one month afterward. Among those who were membrane-free at the one-month mark, an additional 11.2% developed a new membrane over the following three years.
To put that in context, the three-year incidence in the surgical group (12.1% after adjusting for age) was roughly triple the five-year incidence in a comparable group of people who had not had surgery (4.4%). The surgery itself likely accelerates vitreous changes and creates low-level inflammation that promotes membrane growth. This does not mean cataract surgery should be avoided, since most of these membranes are mild, but it is a recognized contributor.
Early vs. Late Stage Membranes
Not all epiretinal membranes cause problems. In the early stage, often called cellophane macular reflex, the membrane is thin and nearly transparent. On imaging, the retina beneath it remains close to normal thickness (around 274 micrometers at the center) and the light-sensing layers of the retina stay intact. Many people at this stage have no symptoms at all, or notice only a faint shimmering quality to their vision.
In the later stage, called preretinal macular fibrosis, the membrane thickens and contracts. The retina beneath it swells noticeably, with central thickness increasing to around 364 micrometers or more. This is the stage that typically produces symptoms: straight lines appearing wavy, blurred central vision, difficulty reading fine print, or a sense that objects look slightly different in size between the two eyes. The transition from early to late stage varies widely between individuals, and some early membranes never progress at all.
Why Some People Are More Susceptible
Beyond age and the specific eye conditions listed above, researchers have not identified clear lifestyle or genetic factors that predict who will develop an epiretinal membrane. The process depends heavily on what happens at the microscopic level during vitreous separation: whether hyalocytes get left behind, whether the inner limiting membrane sustains tiny breaks, and how aggressively the body’s repair cells respond. Two people of the same age can experience vitreous detachment very differently at the cellular level, which is why one develops a membrane and the other does not.
What is clear is that the condition is common. Population studies consistently find epiretinal membranes in a significant percentage of adults over 50, with prevalence climbing steadily with each decade of life. Most of these are mild and asymptomatic, discovered incidentally during routine eye exams.