OCT and OCTA Interpretation
OCT SALIENT FEATURES
Spectral-domain optical coherence tomography (SD-OCT) provides high-resolution cross-sectional images of the retina and is the diagnostic imaging test of choice to assess many vitreoretinal diseases.1
There are several commercially available SD-OCT devices on the market, including Zeiss Cirrus, Heidelberg Spectralis, Topcon 3D OCT, and Optovue Avanti RTVue.
The international nomenclature for OCT panel reported a consensus paper on the retinal and choroidal landmarks on SD-OCT (Figure 3.1).2
OCT INTERPRETATION
OCT interpretation should be done in a systematic fashion and focus on scan quality, pattern, reflectivity, quantitative analysis, and qualitative analysis.1
OCT scan characteristics:
Scan quality:
Some devices provide a quantitative output of signal strength that may be used as a surrogate.
Artifacts should be identified and can be caused by the patient (poor fixation), operator (decentered or out-of-focus scans), or software issues (failed or incorrect segmentation).
Scan pattern—the two most common scan protocols for OCT devices are macular cube and line scans.
FIGURE 3.1 Normal optical coherence tomography (OCT) horizontal raster scan of the left eye with labels of the retina and choroid. Note the nerve fiber layer (NFL) is thicker on the left side, which corresponds to nasal retina and identifies the image as the left eye. IS/OS, inner and outer segments; RPE, retinal pigment epithelium.
Macular cube:
The composition of the scans varies based on device and user input. These are usually moderately densely sampled with variable B-scan densities.
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