Epiretinal membrane (ERM) is an eye condition affecting the macula, the central part of the retina responsible for sharp, detailed vision. It involves the formation of a thin, scar-like tissue on the retinal surface. Optical Coherence Tomography (OCT) is a valuable diagnostic tool for identifying and assessing ERMs.
What is an Epiretinal Membrane?
An epiretinal membrane is a thin layer of fibrous tissue that develops on the inner surface of the retina. This abnormal tissue can contract over time, causing the retina to wrinkle, pucker, or swell. The pulling or traction on the macula can lead to various visual symptoms.
People with an ERM may experience blurred or distorted vision, where straight lines appear wavy or crooked (metamorphopsia). Symptoms also include difficulty reading small print, decreased central vision, and occasionally double vision or light sensitivity. Many ERMs are idiopathic, meaning they develop without a clear cause. They can also form secondary to other eye conditions, such as posterior vitreous detachment (PVD), retinal tears, diabetic retinopathy, eye inflammation, or previous eye surgery.
How OCT Visualizes Epiretinal Membranes
Optical Coherence Tomography (OCT) is a non-invasive imaging technique that provides high-resolution, cross-sectional images of the retina, similar to an ultrasound for the eye. This technology uses light waves to create detailed pictures of the various layers within the retina, allowing eye care professionals to see structures otherwise invisible during a standard eye exam. OCT is more sensitive than traditional clinical examination for diagnosing ERM.
With OCT, the epiretinal membrane appears as a highly reflective, often irregular layer on the inner surface of the retina. This imaging allows for precise visualization of the membrane’s presence, thickness, and attachment to the underlying retinal tissue. OCT scans can reveal specific changes caused by the ERM, such as retinal folds (wrinkles or creases caused by the membrane’s pulling effect), pseudohole formation (a gap in the ERM mimicking a true retinal hole), or foveal depression changes.
OCT is essential for classifying the severity of an ERM and monitoring its progression. It can measure changes in central foveal thickness (CFT), which often increases with ERM and indicates the degree of retinal swelling or traction. The integrity of the inner segment ellipsoid band, another OCT finding, also provides information about the health of the light-sensing cells. These detailed anatomical insights help clinicians make informed decisions about managing the condition.
Managing Epiretinal Membranes
The approach to managing epiretinal membranes varies depending on symptom severity and their impact on vision. For many individuals, especially those with mild ERMs and minimal visual symptoms, observation is a common strategy. Approximately 26% of ERMs may regress spontaneously, while others can remain stable for extended periods. Regular monitoring with OCT and clinical examinations helps track any changes in the membrane or vision.
When an ERM causes significant vision impairment, such as noticeable blurring, distortion, or a reduction in daily activities, surgical intervention is considered. The primary surgical treatment is a pars plana vitrectomy with membrane peel. This outpatient surgery involves making small incisions in the white part of the eye to remove the vitreous gel, the jelly-like substance filling the eye.
Once the vitreous is removed, micro-forceps are used to peel the epiretinal membrane from the retinal surface. In many cases, the internal limiting membrane (ILM), the innermost layer of the retina, is also peeled to further reduce the risk of ERM recurrence and relieve tangential traction. While ILM peeling is a debated topic, some evidence suggests it can improve anatomic success and prevent recurrence. After the membrane is removed, the eye is filled with a sterile saline solution.
Patients can expect a recovery period where vision might initially be worse due to macular manipulation and the presence of an air bubble. Visual improvement usually occurs gradually over several weeks to months, with many patients reporting improved visual acuity and reduced distorted vision. Studies indicate that visual acuity can improve by an average of 8 letters on an ETDRS chart after ERM peeling. Common, temporary side effects include blurred vision and floaters. Potential complications are rare but can include accelerated cataract progression, retinal detachment, or infection.