What Is En Face OCT? A Practical Guide for Optometrists
En face OCT gives you a head-on view of the retina at a specific depth — turning cross-sectional data into a pattern-recognition tool you can read in seconds.
Standard OCT vs En Face OCT
With standard B-scan OCT, you see a cross-section — a vertical slice of the retina, like an ultrasound image. You measure thickness, identify fluid, and assess drusen. It works. But it requires you to synthesize many individual slices mentally to build a 3D picture of what's happening across the macula.
En face OCT changes this. Instead of slicing vertically, it reconstructs the scan data as a head-on view — a C-scan — at a specific retinal depth. Think of it like peeling off a single layer of tissue and looking straight down at it. You see the pattern across the surface, not just the profile.
How En Face Images Are Generated
Both SD-OCT and SS-OCT systems can generate en face views. The system takes the dense volumetric scan — hundreds of B-scans across the macula — and computationally reconstructs a planar image at a chosen depth. You can then navigate through the layers: outer retina, inner segment/outer segment junction, retinal pigment epithelium, choriocapillaris.
SS-OCT systems with their higher scan speeds are particularly good for en face reconstruction because they capture more data with less motion artifact, producing cleaner en face images that are clinically reliable rather than noisy.
Why En Face Helps in Clinical Practice
The primary clinical value of en face OCT is in pattern recognition. Some findings are simply easier to see from above:
- Geographic atrophy: GA margins are often clearer on en face RPE views than on B-scan. You can see the full extent of RPE atrophy and track change over time more reliably.
- Epiretinal membranes: The surface traction pattern is much more apparent en face than in cross-section.
- Drusen mapping: Soft drusen and reticular pseudodrusen both show characteristic patterns en face that help differentiate them.
- Vitreoretinal interface abnormalities: Full-thickness macular holes and lamellar holes show their geometry more clearly en face.
En Face OCT Interpretation: A Practical Workflow
When you open an en face scan, follow this sequence:
- Start at the RPE layer. This is the most informative en face view for most pathologies. RPE elevation, atrophy, and irregularity show clearly.
- Navigate to the outer retina. Look for hyperreflective foci and assess the integrity of the external limiting membrane.
- Check the choriocapillaris layer. Reduced flow signal here can indicate early AMD changes before structural RPE changes are visible.
- Correlate with B-scan. En face tells you where to look; B-scan tells you what's there. Neither replaces the other.
En Face OCT in OCTA Systems
Modern OCTA platforms integrate en face navigation as standard. On systems like the Optovue or Topcon, you can move through the split-spectrum en face layers rapidly with a slider — checking each vascular and structural layer quickly. This is one of the fastest clinical workflows in modern retinal imaging.
The key insight: en face is a viewing angle, not a modality. It applies to structural OCT, OCTA, and combined workflows. If your system supports en face navigation, use it routinely — not just when you're hunting for something specific.
Take our free OCT course — structured lessons from B-scan basics through en face mastery and OCTA integration.
Start Free Course