SPECTRALIS HRA + OCT from Heidelberg Engineering. Optical coherence tomography (OCT) provides high-resolution images of structures at the back of the eye, such as the retina, choroid, and vitreous humour. OCT can be used to identify swelling of the retina. OCT is similar to ultrasonography but uses light instead of sound. Our Doctors use OCT to view disorders of the retina, including macular degeneration, disorders that can cause new blood vessels to develop in the eye, and glaucoma.