Many patients are told they have an epiretinal membrane — sometimes called a macular pucker, cellophane maculopathy, or pre-retinal fibrosis — and immediately wonder whether surgery is needed. The answer, more often than not, is: not yet, and possibly never. But understanding why requires understanding what this condition actually is, how it progresses, and what the surgery involves when it is eventually warranted.
What Is an Epiretinal Membrane?
The retina has a smooth, glistening surface. An epiretinal membrane (ERM) is a thin sheet of fibrous tissue — essentially a scar — that grows on that surface directly over the macula, the central zone of the retina responsible for detailed and colour vision.
This membrane is translucent at first, often causing no symptoms. As it thickens and contracts, it exerts tangential traction on the underlying retinal tissue, distorting the normally flat macular architecture into irregular folds and wrinkles. The result is a characteristic visual distortion — straight lines appear wavy or bent — alongside central blur that spectacle correction cannot fix.
"The macula is not designed to tolerate even small mechanical forces. An epiretinal membrane pulls at the retinal surface with forces that seem trivial — but acting on tissue only a quarter of a millimetre thick, over months and years, that traction is enough to permanently alter its architecture."
— Dr. Chee Wai WongWho Gets It and Why
Epiretinal membranes are surprisingly common. Prevalence estimates from large population studies suggest they affect around 7–11% of adults over 50, rising with age. Most are idiopathic — meaning no identifiable cause is found beyond the normal aging process of the vitreous.
The mechanism in idiopathic cases is linked to posterior vitreous detachment (PVD). As the vitreous gel separates from the retinal surface — a process that occurs in virtually everyone over 60 — it can leave behind glial cells on the macular surface, which then proliferate and form the membrane. In some cases the PVD is incomplete, with vitreous strands remaining attached and contributing to the traction.
Secondary epiretinal membranes occur in the context of other ocular conditions:
- Retinal tears or detachment — either as a cause or in the post-operative period following retinal surgery
- Diabetic retinopathy — proliferative diabetic retinopathy produces fibrovascular membranes that behave similarly but are more complex surgically
- Uveitis — intraocular inflammation promotes fibrous tissue formation
- Retinal vascular occlusion
- High myopia — myopic eyes are at elevated risk, and myopic foveoschisis can coexist
- Post laser or cryotherapy — retinal treatment can occasionally trigger membrane formation
Grading: Not All ERMs Are Equal
Epiretinal membranes are graded by their OCT appearance, which correlates with symptom severity and surgical decision-making. The most widely used classification divides them into four grades.
0
Cellophane maculopathy
Translucent membrane with no retinal distortion. Usually asymptomatic. Watch and wait appropriate in most cases.
1
Mild ERM
Early retinal surface irregularity visible on OCT. Mild metamorphopsia may be present. Surgery rarely indicated at this stage.
2
Moderate ERM
Visible retinal folds and wrinkling with disrupted inner retinal layers on OCT. Noticeable metamorphopsia. Surgery discussion appropriate.
3
Severe ERM
Marked retinal distortion, thickening, and loss of foveal contour. Significant visual impairment. Surgery generally recommended.
Symptoms
The classic presentation is a gradual distortion of central vision — not blur in the way a refractive error causes blur, but a warping or waviness of lines that were previously straight. Reading a newspaper, looking at tiled floors, or viewing window frames are common triggers for noticing the symptom.
A useful test patients can do at home is the Amsler grid — a grid of straight lines with a central dot. Looking at the centre dot with one eye covered: if the surrounding lines appear wavy, bowed, or have a missing area, this warrants prompt assessment. It does not differentiate ERM from other macular conditions, but it is a reliable early-warning signal for any macular problem.
- Metamorphopsia — straight lines appear wavy or bent (the cardinal symptom)
- Central blur — uncorrectable by spectacles
- Micropsia — objects may appear smaller in the affected eye
- Monocular diplopia — mild image doubling in the affected eye only
- Difficulty reading — particularly small print
- No pain — epiretinal membrane is never painful
Importantly, many patients have a significant ERM on OCT with only mild subjective symptoms — while others are highly symptomatic with an apparently modest membrane. This disconnect between the objective finding and the subjective experience is one reason the surgical decision cannot be made on imaging alone.
How It Is Diagnosed
OCT (Optical coherence tomography) is the cornerstone investigation. It provides a cross-sectional image of the retinal layers with micrometre resolution, showing the membrane as a hyperreflective band on the retinal surface, the degree of underlying retinal distortion, foveal contour, retinal thickness, and whether the inner retinal layers are disrupted. OCT also identifies concurrent pathology — macular holes, foveoschisis, or lamellar tears — that may influence surgical planning.
Additional investigations include best-corrected visual acuity, contrast sensitivity testing, and Amsler grid assessment. For surgical planning, the status of the lens (phakic vs pseudophakic) matters — combined cataract and ERM surgery is often the most efficient approach in patients with concurrent lens opacity.
The Surgical Decision: When to Operate
This is the most important — and most nuanced — aspect of epiretinal membrane management. Unlike retinal detachment, which is a surgical emergency, ERM surgery is elective. The decision depends on a careful balance of symptom severity, rate of progression, OCT findings, and the patient's visual demands and general health.
Watch vs Operate — decision framework
- Grade 0–1 ERM with no or minimal symptoms
- Stable appearances on serial OCT over 6–12 months
- Visual acuity 6/9 or better with acceptable quality of vision
- Patient's visual demands are low (e.g. not working, minimal reading)
- Significant medical comorbidities increasing anaesthetic risk
- Fellow eye provides strong compensatory vision
- Moderate–severe metamorphopsia affecting daily activities
- Visual acuity below 6/12 attributable to ERM
- Progressive worsening on serial OCT or clinical assessment
- Disruption of ellipsoid zone (photoreceptor layer) on OCT
- Patient has high visual demands (driving, reading, precision work)
- Binocular diplopia due to interocular image disparity
It is worth stating clearly: surgery does not restore vision to normal. It stops the progression and allows partial recovery. The degree of visual improvement depends on how long the membrane has been present, the extent of underlying retinal damage (particularly to the ellipsoid zone), and the patient's age. Eyes with a short history and intact photoreceptors do better than those where the membrane has been wrinkling the retina for years. This is why, once the decision to operate has been made, proceeding without undue delay is appropriate — but rushing to operate before symptoms are significant is not.
~85%
of patients achieve meaningful visual improvement after ERM surgery
Most improvement occurs in the first 3–6 months, with gains continuing up to 12 months
Surgery: What Happens
ERM surgery is performed as vitrectomy — the same core procedure used for retinal detachment, macular hole, and other posterior segment conditions. It is done under local anaesthesia with sedation, typically as a day procedure. The operation lasts 45–75 minutes.
Vitrectomy — removing the vitreous gel
Three small ports are created in the sclera. The vitreous gel is carefully removed to create clear access to the retinal surface and eliminate any vitreous traction contributing to the membrane.
Membrane peeling
Using fine microsurgical forceps — working on tissue one-tenth of a millimetre thick — the epiretinal membrane is grasped and carefully peeled away from the retinal surface. A staining dye (such as brilliant blue or triamcinolone) is often used to make the translucent membrane visible under the operating microscope.
Internal limiting membrane (ILM) peeling — selective use
In some cases, the surgeon also removes the ILM — the innermost layer of the retina — beneath the membrane. This reduces the risk of ERM recurrence (which occurs in approximately 5–10% of cases without ILM peeling, versus under 2% with). The decision to peel the ILM is made based on the membrane characteristics and surgeon judgement.
Fluid exchange and closure
Unlike macular hole surgery, ERM surgery does not require gas tamponade — meaning there is no face-down positioning requirement post-operatively. The eye is filled with balanced salt solution and the incisions are self-sealing.
No face-down positioning required
This is an important distinction from macular hole surgery. ERM surgery does not use a gas bubble, so patients can sleep, sit, and move normally from the first day post-operatively. Recovery is considerably more comfortable than macular hole repair.
Recovery and What to Expect
The recovery trajectory after ERM surgery is gradual — the retina has been mechanically distorted for months or years, and the tissue takes time to relax and remodel after the offending membrane is removed.
- Day 1: Eye is padded. Vision blurred — expected. Eye drops (antibiotic and anti-inflammatory) to begin.
- Week 1–2: Vision remains variable. Some patients notice early improvement; most still have significant distortion. The retinal folds do not disappear immediately — they resolve gradually over weeks to months.
- Months 1–3: The period of most significant improvement. Metamorphopsia reduces, visual acuity often improves. Reading becomes easier.
- Months 3–12: Slower continued gains. Final visual outcome is generally not assessable until 6–12 months post-surgery.
- Cataract acceleration: Vitrectomy consistently accelerates cataract formation in phakic (non-cataract-operated) patients. Significant cataract develops in the majority within 1–2 years. This is discussed before surgery and often prompts a combined procedure in patients over 55 with any pre-existing lens opacity.
Frequently Asked Questions
I've had an ERM for two years with no change. Do I still need to worry?
Stability over time is actually a reassuring finding. Many ERMs are graded at diagnosis and then followed with serial OCT — and a significant proportion remain stable indefinitely. As long as your vision is acceptable and the OCT is not showing progressive structural damage, continued monitoring rather than surgery is entirely appropriate. The decision to operate should be driven by progressive change or symptom burden, not by the mere presence of the membrane.
Can an epiretinal membrane resolve on its own?
Spontaneous resolution does occur, but it is uncommon — estimated at around 2–5% of cases. More often, once the membrane has formed, it is present permanently unless surgically removed. However, many membranes remain thin and non-progressive, making surgical removal unnecessary. The natural history varies considerably between individuals.
Will surgery fix my metamorphopsia completely?
Surgery significantly reduces metamorphopsia in most patients, but complete resolution is not guaranteed. The degree of recovery depends on how long the distortion has been present and how much structural damage has occurred in the photoreceptor layer. Patients with relatively recent onset, good pre-operative visual acuity, and intact ellipsoid zone on OCT tend to have the best outcomes. Setting realistic expectations — significant improvement rather than perfect resolution — is important in surgical counselling.
I've been told I need ERM surgery but I also need cataract surgery. Can they be done together?
Yes — combined phacoemulsification (cataract extraction with IOL implantation) and vitrectomy for ERM is a well-established procedure. It avoids two separate surgeries, eliminates the need for a second anaesthetic, and prevents the accelerated cataract formation that would otherwise follow vitrectomy alone. For patients over 55 with any visible lens opacity, combined surgery is often the recommended approach. I have published on combined cataract-vitrectomy surgery and perform it regularly.
Can the membrane come back after surgery?
ERM recurrence after surgery is uncommon — occurring in approximately 2–5% of cases when the internal limiting membrane is also peeled during the operation. Without ILM peeling, recurrence rates are somewhat higher. Recurrent membranes can be re-operated, though the surgical plane is less well defined the second time.