What is volumetric OCT used for?

• A. Single cross-sectional scan
• B. Multiple scans following a radial pattern to produce a volume measurement (thickness map)
• C. Angiography
• D. Color fundus photography

Answer: (B)

Volumetric OCT works by collecting many adjacent cross-sectional scans across a region to build a three-dimensional data set of the retina. This 3D dataset lets us calculate thickness at thousands of points and create a thickness map (and en face views) over the scanned area. That capability to produce a comprehensive volume measurement is what makes volumetric OCT particularly useful: it reveals regional thinning or thickening that a single slice could miss, helping with conditions like glaucoma (retinal nerve fiber layer thickness), macular edema, and other retinal diseases. A single cross-sectional scan provides only one slice, so it cannot yield a thickness map. OCT angiography focuses on blood flow in vessels, not volume-based thickness, and color fundus photography provides a flat color image of the surface, without depth information.