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Epiretinal Membranes

Epiretinal Membranes

What are Epiretinal Membranes?

ERMs, (also known as cellophane maculopathy or macular puckers), are avascular, semitranslucent, fibrocellular membranes that form on the inner surface of the retina. Most commonly they cause minimal symptoms and can be observed, but in a few cases, they can result in metamorphopsia (visual distortion) and painless loss of vision. Generally, ERMs are most symptomatic when affecting the macula (the central portion of the retina that helps us to distinguish fine detail used for reading and recognizing faces).

Symptoms

Most patients with ERMs show no symptoms; their ERMs are found on a dilated retinal exam or on retinal imaging such as with ocular coherence tomography (OCT). In these cases, patients typically have normal or near-normal vision. However, ERMs can slowly progress, leading to a vague visual distortion that can be perceived better by closing the non- or less-affected eye.

Patients may experience Metamorphopsia – a symptom that causes visual distortion in objects that are normally straight, like door frames or windows. Things may appear to look “wavy” or “crooked,” especially when compared to the other eye. 

In advanced cases, metamorphopsia may lead to severely decreased vision. Occasionally, but not too often, ERMs may also be associated with double vision, light sensitivity, or images looking larger or smaller than they actually are.

Causes

The cause of ERMs is a defect in the surface layer of the retina where glial cells can move through and start to grow in a membranous sheet on the retinal surface. This membrane can appear like cellophane and over time may contract and cause pulling and puckering of the retina, leading to decreased vision and metamorphopsia.

The most common cause of ERM is an age-related condition called posterior vitreous detachment (PVD), where the gel that fills the eye separates from the retina causing symptoms of floaters and flashes. If there is no specific cause apart from the PVD, the ERM is called idiopathic (of unknown origin).

ERMs can be connected with a few other ocular conditions.

Such as:

  • • Prior retinal tears or detachment
  • • Retinal vascular diseases (such as diabetic retinopathy or venous occlusive disease)
  • • They can also be post-traumatic, occurring following ocular surgery
  • • Be associated with intraocular (inside the eye) inflammation.

Diagnostic testing

Most ERM cases can be diagnosed by an eye care provider during a routine exam. Ocular Coherence Tomography (OCT) is an important imaging method used to assess the severity of the ERM (Figure 1). Sometimes, additional testing such as fluorescein angiography is used to determine if other underlying retinal problems have caused the ERM.

Figure 1.

Treatment and prognosis

As long as they are not affecting vision significantly, most ERMs are fairly stable and can be monitored after the initial period of growth. In rare circumstances, the membrane will spontaneously release from the retina, relieving the traction and clearing up the vision. However, if an exam shows progression and/or functional worsening in vision, surgical intervention may be recommended.

There are no eye drops, medications, or nutritional supplements to treat ERMs. A surgical procedure called vitrectomy is the only option for eyes that require treatment. With vitrectomy, small incisions are placed in the white part of the eye, and the vitreous gel filling the inside of the eye is replaced with saline. This allows access to the surface of the retina where the ERM can be removed with delicate forceps, thereby allowing the macula to relax and become less wrinkled. Visual recovery is slow and most eyes experience improvement within 3 months but it may take a year to attain maximal visual acuity improvement.

The risk of complications with vitrectomy is small, with about 1 in 100 patients developing retinal detachment and 1 in 2000 developing an infection after surgery. Patients who still have their natural lens will develop increased progression of a cataract in the surgical eye following surgery.

Figure 2.

Factors affecting visual outcome include:

  • • Length of time the ERM has been present
  • • The degree of traction (or pulling)
  • • The cause of the ERM Idiopathic ERMs have a better prognosis than eyes with prior retinal detachment or retinal vascular diseases
  • • Surgery for ERM has a good success rate, and most patients experience improved visual acuity and decreased metamorphopsia following vitrectomy.

Risk Factors

The risk of developing an ERM increases with age, and persons with predisposing ocular conditions may develop ERM at an earlier age. The most common association, however, is PVD. Studies have shown that 2% of patients over age 50 and 20% over age 75 have evidence of ERMs, although most do not need treatment. Both sexes are equally affected. In about 10% to 20% of cases, both eyes have ERMs, but they can be of varying degrees of severity.