What is Epiretinal Membrane?
In 1865, a scientist named Iwanoff first described a condition called an epiretinal membrane (ERM). This is the growth of tissue on the surface layer of the retina, which is the part of the eye that captures the light and sends it to your brain to form an image. The ERM condition typically affects the back part of your retina over an area called the macula. Here, it shows up as a greyish, nearly-transparent membrane without any blood vessels, sitting on the surface layer of your retina. This condition is known by many different names, including macular pucker and cellophane maculopathy.
The cause of ERM is unknown. It can just happen on its own or it can occur as a result of eye injury, after eye surgery, or due to chronic eye disorders. The condition gradually affects your central vision and causes distorted vision. The best way doctors can diagnose and assess how much the epiretinal membrane is affecting the shape of the retina is through a procedure called an Optical Coherence Tomography (OCT). If treatment is needed, your doctor will likely recommend a retina surgery known as pars-plana vitrectomy (PPV), along with ERM and ILM peeling to remove the tissue.
What Causes Epiretinal Membrane?
We don’t fully understand what causes an epiretinal membrane (ERM), which is a thin layer of tissue that forms over the retina, the light-sensitive layer of tissue in the back of your eye. Most of the time, ERMs happen without any known reason, a condition referred to as idiopathic ERM (IERM).
However, there are known factors that can lead to a secondary ERM. These can include eye injuries, procedures done to the inside of the eye, diabetes-related eye problems, blocked veins in the retina, long-lasting swelling in the retina, inflammation inside the eye, the retina detaching from the back of the eye, and tumors inside the eye.
As you get older, the risk of getting an ERM goes up. Other risks include already having an ERM in the other eye, or having a condition known as posterior vitreous detachment (PVD) where the gel-like substance inside the eyes shrinks and separates from the retina.
The ERM condition has a few other names such as cellophane maculopathy, macular pucker, preretinal fibrosis, and preretinal membrane. According to a large study involving 49,000 individuals, being older and being female were found to be significant risk factors for developing an ERM.
Risk Factors and Frequency for Epiretinal Membrane
Epiretinal membranes, the most common type of which is called idiopathic, are often seen in people over the age of 50, affecting both males and females equally. Age, having diabetes, and high cholesterol levels are known factors that increase the risk of these membranes. It’s noteworthy that in the United States, specific ethnic groups have been observed to have a higher prevalence of epiretinal membranes, with the Chinese population being most affected.
In one study that had thousands of mixed-race participants, it was discovered that about 9% of them had some form of epiretinal membranes. These membranes are grouped into two categories: preretinal macular fibrosis, characterized by retinal folds, and cellophane macula reflex, which doesn’t involve retinal folds. Higher risks of having these conditions were observed among older and female participants.
In a separate Australian study, it was found that among those aged 49 and above, the inception of Epiretinal membranes in the first eye was 5.3%, and there was a progression from early to an advanced stage in 9.3% of the cases. Furthermore, over a five-year period, some participants were found to develop the condition in their second eye as well.
- Epiretinal membranes, especially the idiopathic type, commonly affect people over 50.
- Both males and females are equally likely to have it, with about 20% of people over 75 having an epiretinal membrane.
- A large multi-ethnic US study showed a higher prevalence among the Chinese demographic.
- A significant study involving approximately 40,000 participants revealed that 9% had some form of epiretinal membrane.
- Classified into two groups, these membranes can take the form of preretinal macular fibrosis (with retinal folds) or cellophane macula reflex (without retinal folds).
- Older participants and females demonstrated a higher risk of developing these membranes.
- A long-term Australian study revealed that the incidence of these membranes in the first eye was 5.3%, with a five-year progression rate to an advanced stage of 9.3%.
- Additionally, over five years, 13.9% of subjects developed the condition in their second eye.
Signs and Symptoms of Epiretinal Membrane
An epiretinal membrane (ERM) is a condition that often shows no symptoms and is usually found during routine eye check-ups. However, some people with ERM may experience various changes in their vision. This can disrupt everyday activities like reading and writing, and significantly affect quality of life.
- Distorted vision (metamorphopsia)
- Things appearing smaller (micropsia) or larger (macropsia)
- Flashing lights (photopsia)
- Reduced sharpness of vision
- Double vision (diplopia)
- Loss of central vision
People without symptoms should monitor their vision regularly using a tool called an Amsler grid. It’s also important to inform the doctor about any previous eye injuries, instances of seeing floaters or flashes of light, and medical conditions such as diabetes, high blood pressure, and high cholesterol levels. ERM can cause changes in the retina, like retinal striae, folds, and progressive contracture, leading to the illusion of a hole in the macula (macular pseudohole). In rare cases, the membrane might separate on its own, causing floaters that seem to sit just in front of the macula.
Testing for Epiretinal Membrane
Idiopathic epiretinal membrane (IERM) is often found in people 60 and older and affects all genders alike. If you’re experiencing distorted vision, your eye doctor will likely conduct a number of tests, including a visual test, an Amsler grid test, and a dilated eye exam. These tests help determine what’s causing the distortion in your vision. In particular, the Watzke Allen test helps differentiate between a full-thickness macular hole and a pseudohole. These tests are done using a special microscope called a slit-lamp.
Through the slit-lamp exam, if your retina, which is the tissue toward the back of the eye, looks shinier than normal and has a fine, wrinkly texture, this could suggest that you have an epiretinal membrane (ERM), also known as a macular pucker. ERMs come in two forms; a mild early form called cellophane macular reflex and a severe later form known as preretinal macular fibrosis.
If you have cellophane macular reflex, you’ll see a thin, clear membrane covering the center of your retina (the macula). It won’t distort your vision or make the images look weird. When your doctor examines your eye, they’ll likely see a shiny, silk-like reflection in the center of your retina. Preretinal macular fibrosis is more serious. Here, the membrane has thicken and contracted, causing folds in the retina. This can distort your vision and may cause metamorphopsia, a condition causing straight lines to appear wavy or blank. When the doctor looks at your retina, they might see a semi-clear membrane covering up the details of the retina with folds, lines, and twisted blood vessels. Severe cases may also cause bleeding in the retina, swelling, and even holes in the macula.
Optical coherence tomography (OCT) is a highly sensitive scan that gives a detailed view of the retina and is the preferred method for diagnosing epiretinal membranes and vitreomacular traction (VMT). OCT shows ERMs as bright, irregular layers on the surface of the retina that may look corrugated or have peg-like structures attached to the retina. In severe cases, the inner part of the retina may develop folds and the macular can thicken. Also, cysts or fluid-filled spaces can develop. Both ERM and VMT often happen together.
Researchers have proposed a grading system for ERMs based on OCT results. The four stages are as follows:
Stage 1: Mild, thin ERM with normal depression in the retina.
Stage 2: ERM with widened outer nuclear layer of cells and loss of the normal depression in the retina.
Stage 3: ERM with continuous sheets of misplaced inner cells crossing the whole area of the retina.
Stage 4: Thick ERM with continuous sheets of misplaced inner cells and disturbed retinal layers.
From stages 1 through 4, vision tends to get worse progressively. Another classification has also been proposed based on whether the abnormality involves the center part of the retina or not.
Other tests like fundus fluorescein angiography or an optical coherence angiography (OCT-A) can help spot other retinal diseases causing secondary ERM.
Treatment Options for Epiretinal Membrane
Epiretinal membrane (ERM), which is a thin layer that forms over the retina in the eye, doesn’t require treatment in most patients, especially when it doesn’t affect their vision or cause significant visual changes (metamorphopsia). Studies suggest that only 20% of ERMs worsen over five years while 26% even improve, and 39% stay the same.
The best form of treatment for ERM, if needed, is surgery, primarily aimed at preserving or improving vision, reducing symptoms like visual distortions or double vision, and improving the patient’s quality of life. Numerous factors affect the potential visual results from this treatment, including how long the patient has had the condition, the severity of traction (or pulling) on the retinal surface, and the cause of the ERM. When ERM forms spontaneously, without any obvious cause (idiopathic), the prognosis is generally better than when it is caused by an eye disease.
Non-surgical treatment options include a drug called ocriplasmin. The FDA has approved ocriplasmin for treating a specific condition known as symptomatic vitreomacular traction (VMT). The drug can alleviate the pulling on the retinal surface associated with ERM, possibly relieving symptoms of metamorphopsia. However, it doesn’t affect the ERM itself. The efficacy of ocriplasmin in treating patients with both VMT and ERM is a topic of ongoing debate.
In terms of surgical treatment, the standard procedure involves a technique called pars-plana vitrectomy (PPV) along with the removal (peeling) of ERM and the inner limitant membrane (ILM). This process involves removing some or all of the vitreous humor – a jelly-like substance in the eye – and has been effectively used for several years. Alongside ERM removal, often the ILM is also removed as it is believed to provide a base for the growth and proliferation of unwanted cells causing ERM. This technique has significantly improved following the introduction of various staining dyes that assist surgeons in accurately identifying the areas that need peeling.
The most common issue after a vitrectomy is the progression of cataract, a clouding of the natural lens in the eye. If a cataract is present, it might be advisable to combine cataract removal with the vitrectomy to ensure a clear vision for the surgery and to obviate the need for a second operation later on.
Using dyes to aid ILM peeling has resulted in improved visual outcomes, lower recurrence rates, and less distortion in the retina. However, there is a concern that ILM peeling might damage some important cells in the retina, called Müller cells, leading to an ongoing debate about the trade-off between the potential benefits of the technique and the potential risks. Several studies have been done comparing the outcomes of removing the ERM only versus removing both the ERM and the ILM. It appears that removing both the ERM and the ILM leads to improved vision over the long term and lower rates of ERM return, although removal of the ERM alone can also be effective in reducing retinal thickness.
What else can Epiretinal Membrane be?
The look of an epiretinal membrane (ERM) in the eye is very distinctive. However, at their early stages, there are a few conditions that look similar to it:
- Fine vessel tortuosity, which happens when there is a combined growth of the retina and RPE (the layer beneath the retina)
- A membrane appearing over the retina, which could be a sign of proliferative vitreoretinopathy (a scar tissue on the retina) or tractional retinal detachment (when the retina is pulled from its normal position).
What to expect with Epiretinal Membrane
An Epiretinal membrane (ERM), or a thin film that develops on the surface of the retina (the light-sensitive tissue at the back of the eye) generally doesn’t cause symptoms at first and often has a good outcome. According to the Blue Mountains study, about 39% of these membranes don’t get worse over time. However, if an ERM does progress, it can reduce vision and cause a disturbing visual distortion known as metamorphopsia.
For ERMs that continue to worsen, a type of eye surgery known as pars plana vitrectomy with membrane and ILM peeling is usually very effective. It can improve vision and diminish the occurrence of metamorphopsia. That said, ERMs can come back in some cases, at a rate, which can be anywhere from 1% to 21%.
Why might vision not fully recover, or why might an ERM come back? It usually happens if not all of the membrane is removed during surgery. An additional procedure called an ILM peel can sometimes help, by removing the layer of retinal cells where an ERM might form again. A study has found that if there is a disruption in the photoreceptor cells (the cells in the retina that begin the process of seeing) or delay in retinal signal processing detected by tests like OCT (optical coherence tomography) or a multifocal electroretinogram, it can predict poor vision recovery after ERM surgery. So far, the most important risk factor for post-surgery vision recovery is how long the ERM has been present.
Possible Complications When Diagnosed with Epiretinal Membrane
Epiretinal membrane (ERM) can lead to several eye complications. These complications might include:
- Increased progression of nuclear sclerosis, which is a type of cataract
- The creation of tears or even a detachment in the retina
- Damage to the macula (the central area of vision) due to trauma or light
- Endophthalmitis, which is an inflammation inside the eye
- The development of a macular hole
- Bleeding in the gel-like substance that fills the eye, known as a vitreous hemorrhage
- Small bleedings in the retina, known as retinal petechiae or hemorrhage
- A condition known as the dissociated optic nerve fiber layer
Preventing Epiretinal Membrane
Patients should know that most epiretinal membranes – thin layers that can form over the eye’s retina and might cause problems with vision – usually don’t need any intervention if they aren’t affecting their sight or causing distorted vision, also known as metamorphopsia. Checking your vision periodically with Amsler grid charts, which are simple tools to detect vision problems, can help you spot early signs or increasing metamorphopsia. It’s also helpful to monitor your vision in each eye separately to catch any early changes in your central vision.
Your doctor might tell you about surgical procedures for treating the epiretinal membrane (an operation involving the removal of that thin layer from your retina). These surgeries are typically very successful in improving issues related to vision clarity and the overall quality of life. Being informed about these options and discussing with your doctor can help set a clear and realistic expectation of what to expect after the treatment.
