Optical coherence tomography (OCT) is a non-invasive imagine test that uses light waves to take cross-section pictures of your retina, the light sensitive tissue lining in the back of the eye. The OCT allows us to measure the thickness of your retina and allows doctors to look at the optic nerve. This can provide guidence for treatment of glaucoma, age-related macular degeneration and diabetic retinopathy. This test often requires dilation drops. The test lasts 5 to 10 minutes.