Epiretinal Membrane (ERM)

Overview

An epiretinal membrane (ERM) is a membrane of glial cells and laminocytes attached to remnants of the vitreous cortex on the retinal surface. Clinically, it appears as wrinkling of the retinal surface with an abnormal sheen or reflectivity.

On OCT, it can be seen as a thin hyper-reflective layer above the internal limiting membrane (ILM). It can cause tractional stress on the underlying retina and may be associated with wrinkling of the retinal surface, loss of the foveal pit, retinal thickening and cystic spaces. In advanced cases, there can also be disruption of the inner segment elllipsoid zone and photoreceptor outer segments which can cause further reduction in visual acuity.

ERM's are mostly commonly idiopathic (likely resulting from anomalous posterior vitreous detachment), but can also occur as a result of trauma, inflammation, intraocular surgery, tumours, vascular disease and retinal tears or detachments.

Case Examples

  • Case 1: ERM

    A 63 year old Asian male with best corrected visual acuity of 6/9.5+ (20/32+) in the right eye. Testing with an Amsler grid revealed no distortion of the vision in the right eye.

    Fundus photograph and red-free image (right eye)

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    Fundus photograph and red-free image (right eye)

    Fundus photos show radial retinal striations centered on a point temporal to the optic disc. These striations are most easily appreciated on the red-free image.

    Spectralis OCT line scan (right macula)

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    Spectralis OCT line scan (right macula)

    OCT shows the presence of an ERM in the area of the retinal striations. A localised traction is evident on the retinal surface and hypo-reflective spaces are seen between the ERM and the ILM, however no cystic spaces are noted. The foveal pit depression is undisturbed.

  • Case 2: ERM with associated retinal thickening

    A 59 year old Asian female with best corrected visual acuity of 6/7.5+ (20/25+) in the right eye. Testing with an Amsler grid showed mild generalised waviness of the grid.

    Fundus photo and red-free image (right eye)

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    Fundus photo and red-free image (right eye)

    Retinal photos show the presence of significant retinal striations radiating out from the macular centre. This is most easily appreciated on the red-free image.

    Spectralis OCT line scan (right macula)

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    Spectralis OCT line scan (right macula)

    The ERM can be seen on the surface of the inner retina. There is significant traction present causing hypo-reflective spaces between the ERM and ILM, retinal thickening and a loss of the foveal depression. No intra-retinal cystic changes are evident.

    Spectralis OCT volume scan (right macula)

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    Spectralis OCT volume scan (right macula)

  • Case 3: ERM with intra-retinal cystic spaces

    A 70 year old Caucasian male with best corrected visual acuity of 6/12 (20/40) in the right eye. Central distortion was noted on testing with an Amsler grid.

    Fundus photograph and red-free image (right eye)

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    Fundus photograph and red-free image (right eye)

    Funduscopy shows an ERM at the right macula. This is causing an apparent increase in vascular tortuosity as the membrane causes retinal wrinkling.

    Spectralis OCT line scans (right macula)

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    Spectralis OCT line scans (right macula)

    OCT shows an ERM on the retinal surface. Contraction of this ERM has caused retinal thickening and the development of intra-retinal cystic spaces.

  • Case 4: ERM with ectopic inner foveal layers

    A 64 year old Asian female with best corrected visual acuity of 6/7.5 (20/25) in the left eye. Testing with an Amsler grid revealed distortion of the vertical lines while the horizontal lines appeared unaffected.

    Fundus photograph and red-free image (left eye)

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    Fundus photograph and red-free image (left eye)

    Fundus photos show retinal striations radiating out from the left temporal macula and an irregular sheen.

    Spectralis OCT line scan (left macula)

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    Spectralis OCT line scan (left macula)

    Images 1 and 2 both show distortion of the foveal pit and ectopic inner foveal layers (defined as 'presence of a continuous hyporeflective or hyperreflective band...across the foveal region') identified by the blue arrows. An ERM can be seen on the retinal surface.

Differential Diagnosis

Vitreomacular traction

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ILM detachment

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Choroidal folds

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Retinal neovascularisation

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References

Govetto A, Lalane RA, Sarraf D, Figueroa MS, Hubschman JP. (2017) Insights Into Epiretinal Membranes: Presence of Ectopic Inner Foveal Layers and a New Optical Coherence Tomography Staging Scheme. Am J Ophthalmol. 175:99-113.

Stalmans, P. Duker, J. Kaiser, PK. Heier, JS. Dugel, P et al. (2013) OCT-Based interpretation of the vitreomacular interface and indications for pharmacologic vitreolysis. Retina Volume 33 - Issue 10