Epiretinal membrane is a commonly under-recognised cause of impaired vision. It is a fibrous membrane resulting from cellular proliferation on the retinal surface, usually involving the macula.
Eye care professionals should recognise that Epiretinal membranes (ERM) are a common cause of reduced vision and be aware of their clinical features. Advances in surgical techniques have led to improved outcomes and reduced thresholds for ERM surgery.
The prevalence of ERM in Australia is 10 per cent in people aged over 60 years. Early ERMs are asymptomatic. Blurring, or distortion of vision, may develop as the ERM grows, exerting traction on the macula and occasionally causing severe vision loss.
The majority of ERMs are idiopathic. A posterior vitreous detachment is present in over 90 per cent of cases and may be an important factor in ERM formation. ERM may be associated with retinal tears, retinal detachment, retinal vein occlusion, diabetic retinopathy, uveitis, trauma or intraocular surgery. Depending upon the cause, ERMs may also contain retinal pigment epithelial cells, glial cells, macrophages, or myofibroblasts.
Eye care professionals should recognize that ERMs are a common cause of reduced vision and be aware of their clinical features
Diagnosis
ERMs can be subtle and easily missed on cursory examination. The following signs should alert you to the presence of an ERM (see figure 1):
- Loss of the normal foveal reflex
- A subtle white macular sheen, known as ‘cellophane maculopathy’ which looks like a piece of glad wrap covering the macula
- Straightening and tortuosity of the retinal vessels resulting from traction exerted by an ERM
- Retinal tension lines caused by contraction of an ERM
- A macula pseudo-hole resulting from a defect in an ERM – this may look like a macular hole
- Opaque white fibrous tissue on the macula surface, known as premacular fibrosis
- Macular oedema resulting from ERM traction on retinal vessels, most apparent on fluorescein angiography
Figure 1. Pre-coperative photo showing ERM with loss of the forveal reflex, retinal tension lines, and cellophane maculopathy
Figure 2. Post-operative photo following sutureless vitrectomy with ERM peeling with restoration of the forveal reflex, reduced retinal tension lines and no cellophane maculopathy
Optical coherence tomography (OCT) enables early identification of ERMs and may show foveal contour abnormalities, retinal folds or macular thickening. Newer spectral domain OCT scanners enable 3D visualisation of vitreoretinal relationships which I have found useful for surgical planning prior to ERM surgery.
ERM Treatment
Vitrectomy surgery is a common and effective treatment for ERM. It reduces distortion and often improves visual acuity (VA).
Traditionally, vitreoretinal surgeons used an arbitrary VA cut-off such as 6/18 before offering ERM surgery. However, improvements in surgical technology, better outcomes, and increasing patient expectations have led to reduced thresholds for ERM surgery.
In eyes with VA of 6/9 or better and progressive ERM, should surgery be performed early or delayed until the VA decreases to 6/18? Research confirms that the potential for improvement decreases with prolonged observation and the best predictors of outcome following ERM surgery are preoperative VA and duration of symptoms. If surgery is delayed until VA decreases from 6/9 to 6/18 over a period of five years, the visual result will be less favourable than if surgery was performed when the VA was 6/9.
My decision to offer surgery is based on patient symptoms and visual function. I often perform ERM surgery in patients with good VA with significant distortion or an occupational requirement for good stereopsis.
Sutureless vitrectomy with ERM peeling is my preferred technique for removal of the vitreous and ERM. This is a form of keyhole surgery performed as a short day case procedure using local anaesthesia.
Additional intravenous sedation is effective in relaxing even the most anxious patients. Compared to traditional vitrectomy techniques which require sutures, a sutureless vitrectomy enables a rapid, comfortable recovery (due to the absence of suture related foreign body sensation) and high rates of patient satisfaction.
Complications of ERM surgery are uncommon but include endophthalmitis, retinal detachment and macular oedema. Cataracts develop in most phakic eyes within two years of ERM surgery, necessitating cataract surgery.
Dr. Simon Chen MBBS, BSc, FRCOphth, FRANZCO is a Medical and Surgical Retina specialist at Vision Eye Institute in Sydney, consulting in Bondi Junction, Chatswood, Drummoyne and Hurstville. He is Honorary Clinical Senior Lecturer at the University of Auckland. His special interests include intravitreal drug treatments for age related macular degeneration and sutureless retinal surgery for retinal detachments, ERMs and macular holes.
Dr. Chen has published over 20 peer reviewed papers and textbook chapters. He is an investigator for international clinical trials of new treatments for retinal disease and reviews papers for leading ophthalmic journals.
Dr. Chen graduated in Medicine from the University of London in the UK, and trained in Ophthalmology at the teaching hospitals of the Universities of Oxford and Cambridge. He completed Vitreoretinal Fellowship training at international centres of excellence including the Oxford Eye Hospital and the Lions Eye Institute.
| ERM Case Study |
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A 58 year old male jewellery maker complained of increasing difficulty seeing fine details on jewels during the past year. His VA was 6/6 OD, 6/9 OS. Examination showed an isolated left ERM (see figure 1). Sutureless vitrectomy with ERM peeling was performed. His left VA improved to 6/6 at two months post-op (see Figure 2). |
