Epiretinal membrane (ERM) is one of the most frequently encountered macular conditions in clinical practice. While many patients remain asymptomatic or experience only mild visual disturbance, others develop progressive retinal distortion with significant functional impairment. The challenge for referrers is determining which patients are likely to remain stable and which may benefit from earlier vitreoretinal assessment.
Optical coherence tomography (OCT) has transformed the management of ERM, allowing clinicians to move beyond simply confirming the diagnosis and instead evaluate structural biomarkers that correlate with visual function and postoperative outcomes.
Not All ERMs Behave the Same
Most idiopathic ERMs develop following posterior vitreous separation and remain relatively stable for years. Others progressively contract, causing retinal thickening, distortion of the foveal architecture and disruption of the normal retinal layers.
Clinical symptoms remain important, but OCT often provides the earliest indication that retinal traction is becoming visually significant.
Patients may report:
- Progressive reduction in visual acuity
- Metamorphopsia
- Difficulty reading despite appropriate refractive correction
- Reduced contrast sensitivity
- Micropsia
Importantly, visual acuity alone may underestimate functional impairment. Patients with relatively good Snellen acuity can still experience significant distortion affecting reading and other activities of daily living.
OCT Biomarkers That Matter
Beyond confirming the diagnosis, OCT can provide valuable prognostic information to guide referral timing and patient counselling.
Ectopic Inner Foveal Layers (EIFL) are associated with more advanced disease and poorer visual outcomes, both before and after surgery, reflecting chronic retinal traction and remodelling.
Disorganisation of the Retinal Inner Layers (DRIL) is another emerging biomarker linked to reduced visual function and may indicate irreversible disruption of the retinal architecture.
Additional OCT features that may suggest progression include progressive retinal thickening, loss of the normal foveal contour, intraretinal cystic changes, vitreomacular traction and disruption of the ellipsoid zone.
As structural changes often precede significant vision loss, serial OCT imaging plays a crucial role in identifying patients who may benefit from earlier vitreoretinal assessment.
OCT Biomarkers That Matter
Govetto Staging
The Govetto classification stages epiretinal membranes according to progressive structural changes seen on OCT. As disease advances from Stage 1 to Stage 4, increasing retinal distortion and loss of normal foveal architecture are associated with worsening visual function and a reduced likelihood of complete visual recovery following surgery.
Govetto Stage | Key OCT Finding | Clinical Significance |
Stage 1 | Preserved foveal pit | Mild disease; often observation |
Stage 2 | Loss of foveal pit | Progressive traction |
Stage 3 | Development of EIFL | Worse visual function; earlier referral should be considered |
Stage 4 | EIFL with disrupted retinal architecture | Advanced remodelling and poorer postoperative prognosis |
Ectopic Inner Foveal Layers (EIFL)
One of the strongest OCT predictors of visual prognosis is the presence of ectopic inner foveal layers (EIFL).
EIFL represents the extension of inner retinal layers across the central fovea, reflecting chronic traction and loss of the normal foveal depression. Several studies have demonstrated that increasing EIFL is associated with:
- Worse baseline visual acuity
- Greater metamorphopsia
- Reduced postoperative visual improvement
- More advanced disease
Patients demonstrating established EIFL generally have more chronic pathology and may achieve less visual recovery following membrane peeling compared with patients referred earlier in the disease course.
Disorganisation of the Retinal Inner Layers (DRIL)
Another emerging prognostic marker is disorganisation of the retinal inner layers (DRIL).
DRIL refers to the inability to distinguish the normal boundaries between the ganglion cell layer, inner plexiform layer, inner nuclear layer and outer plexiform layer on OCT.
Although initially described in retinal vascular disease, DRIL has also been associated with poorer visual function in patients with ERM. Increasing DRIL appears to reflect disruption of normal retinal neuronal architecture and correlates with reduced visual acuity and poorer functional outcomes.
When present alongside EIFL, DRIL suggests more advanced retinal remodelling and may indicate a narrower window for optimal surgical intervention.
Additional OCT Features Worth Monitoring
Other OCT findings that may indicate progression include:
- Progressive retinal thickening
- Increasing loss of the normal foveal contour
- Progressive retinal folds or surface wrinkling
- Intraretinal cystic spaces
- Vitreomacular traction
- Disruption of the ellipsoid zone or outer retinal layers
Serial OCT imaging is often more informative than a single scan, allowing clinicians to identify subtle structural progression before significant visual loss occurs.
When Should Patients Be Referred?
Referral should be considered when patients demonstrate:
- Progressive visual symptoms, particularly metamorphopsia
- Declining visual acuity
- Progressive structural changes on OCT
- Development of EIFL or DRIL
- Outer retinal disruption or increasing retinal thickening
- Diagnostic uncertainty, particularly where vitreomacular traction or a lamellar macular hole is suspected
Patients with minimal symptoms and stable OCT findings can often be monitored safely within primary eye care using periodic review and serial OCT imaging.
Clinical Take-Home Messages
- OCT has become central to the assessment and monitoring of epiretinal membrane.
- Visual acuity alone does not fully reflect functional impairment. Near visual acuity should be assessed for functional impact.
- EIFL and DRIL are emerging biomarkers associated with disease severity and visual prognosis.
- Progressive OCT changes often precede significant loss of vision.
- Early referral allows discussion of management before chronic retinal remodelling limits visual recovery.
As OCT technology continues to evolve, structural biomarkers are increasingly helping clinicians identify patients who are most likely to benefit from timely vitreoretinal assessment and intervention.