Optical coherence tomography (OCT) enables ophthalmologists to measure retina thickness on a cellular level and has revolutionized the way we practice ophthalmology.
Considering how ubiquitous this technology is, it’s essential that you are able to interpret these 3D reconstructions. But have no fear! By practicing these three steps, you will be better able to accurately (and comfortably) use OCT to your clinical advantage!
1. Know what’s normal.
Familiarize yourself with how a normal OCT looks. There should be nine layers of the retina itself, alternating in light and dark bands. We also want to consider the vitreoretinal interface above and the choroid below. The foveal depression should be symmetric and centrally located in the image.
Layers
Inner retina
- Nerve fiber layer
- Ganglion cell layer
- Inner plexiform layer
- Inner nuclear layer
Outer retina
- Outer plexiform layer
- Outer nuclear layer
- External limiting membrane
- Photoreceptor IS/OS (inner segment/outer segment)
- Retinal pigment epithelium
2. Locate and describe the pathology.
Now that you know the layers, figure out where the pathology is, and try to describe it. Generally speaking, pathology will be in the vitreoretinal interface, inner retina, outer retina, Bruch’s membrane/retinal pigment epithelium (RPE) layer or choroid.
3. Correlate clinically and make the diagnosis.
We often joke about the “clinical correlation required” comment on radiology reads; however, considering the clinical information at hand can often give you important tips to help with the diagnosis. Here are some guidelines to help you with your diagnosis:
Epiretinal membrane
- Locate pathology: Above the internal limiting membrane (ILM), so in the vitreoretinal interface
- Describe pathology: Hyperreflective membrane causing traction on the inner surface of the retina
- Correlate clinically: Older patient, often with a posterior vitreous detachment (PVD), describing central distortion
Diabetic macular edema
- Locate pathology: In the inner nuclear layer (INL) and outer plexiform layer (OPL)
- Describe pathology: Hyporeflective cysts
- Correlate clinically: Diabetic patient, central vision blurry, often worse with worsened diabetic retinopathy
Central serous retinopathy
- Locate pathology: Outer retina, under RPE
- Describe pathology: Hyporeflective serous fluid
- Correlate clinically: Typically younger male, high-strung patient under stress or taking steroid medications or hormones
Drusen/Age-related macular degeneration (AMD)
- Locate pathology: Outer retina, Bruch’s/RPE
- Describe pathology: Hyperreflective bumps
- Correlate clinically: Usually older, fair-skinned patients, minimal or no symptoms
Remember, interpreting OCTs will get easier with a little practice, and you’ll be able to treat your patients’ glaucoma and other retinal conditions confidently and efficiently.
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Jessica D. Randolph, MD, is a vitreoretinal surgeon in Richmond, Va. She has been on the
YO Info editorial board since 2021.