OCT is short for Optical Coherence Tomography. The OCT takes a non-invasive, non-contact optical biopsy of the retina with a resolution so fine that an OCT scan could be called an in vivo histological section of retinal tissue.

The OCT allows doctors to look for early indications of diabetic retinopathy, macular degeneration, and nerve fiber loss in diseases such as glaucoma. The OCT gives doctors a computer generated cross-section of any area of the retina.