Sunday, June 10, 2018

epiretinal membrane

Epicupcake membrane

What is an epiretinal membrane?
An epiretinal membrane (ERM), also known as a macular pucker or cellophane maculopathy, is a thin layer of tissue that forms on the inner surface of the retina (the tissue that lines the back of the eye). **Look out, jargon ahead.** Specifically, an ERM forms when glial cells proliferate in a sheet between the internal limiting membrane (ILM) of the retina and the posterior hyaloid membrane of the vitreous. **You survived. No more jargon.** When ERMs contract, they pull on the retinal tissue and vessels beneath them. This causes wrinkling and distortion of the retina.

ERMs occur most often in those over 50 years of age, and their prevalence increases with age. ERMs effect males and females almost equally. Most are idiopathic (meaning unknown cause), but they can also occur secondary to posterior vitreous detachments (PVDs), eye surgery, diabetic retinopathy, eye inflammation, and trauma. ERMs can occur in both eyes in up to 20-35% of cases (1).

What are the symptoms?
Most ERMs have no symptoms and are found incidentally on routine eye exams. In those cases where symptoms are noticed, distorted vision (metamorphopsia) is the most common symptom. Decreased vision can occur as well, especially if the ERM is located at the macula (the part of the retina that is responsible for your central, sharpest vision).

How is it diagnosed?
ERMs are diagnosed by looking into the back of the eye during a dilated eye examination. An ERM appears as a shimmery reflectance over the retina, almost like fine gold glitter. If the ERM contracts, puckering or wrinkling of the retina and vessels beneath it may be noted. ERMs can be seen on retinal photos and OCT scans.

Infrared SLO of an ERM: you can see the wrinkling of the retina

Optical Coherence Tomography (OCT) is helpful for imaging and monitoring ERMs. An OCT scan provides a cross-sectional view of the retina, so you can easily see the membrane and how it is distorting the retina beneath it. Sometimes, OCTs can uncover ERMs before they are noticeable in the microscope.

OCT scan of an ERM: the white (hyper-reflective) line above the retina is the ERM

How is it treated?
In the majority of cases, ERMs are just monitored. However, ERMs can cause pseudo-holes and cysts in the retina. If vision is affected significantly, or if the ERM is threatening to cause significant vision loss, surgical intervention may be advised. If surgery is pursued, the gel part of the eye (the vitreous) is first removed in a procedure called a pars plana vitrectomy. Then, the ERM is peeled, and the internal limiting membrane (ILM) of the retina is sometimes peeled as well. Here is a neat video of the procedure (note: you will see that a dye is used to make the membrane more visible). In most cases, visual symptoms of distortion decrease after the membrane is peeled. Visual acuity may improve as well, but it often will not return to normal. ERMs may recur after removal.

Retinal photo of an ERM (note the gold shimmery appearance of the retina in the center of the image) with a pseudohole (the darker red circle in the middle of the gold shimmer)

CliffsNotes: An ERM is a sheet of cells that forms on the innermost layer of the retina. They are often symptomless and discovered on routine eye exam (so it's important to get those). Most of the time, ERMs are monitored but there are some occasions where they need to be peeled. 

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