OCT is the abbreviation for Optical Coherence Tomography. This method uses harmless laser rays to analyze the optic nerve, as well as neurites (axons) around the optic nerves and in the macula.
Each layer and each structure of the retina reflects these weak laser beams in a different way. Reflection is measured and carried through with a computer system to finally create images. These images present a precise insight into the finest structures and changes in the retina.
A big advantage of this examination is that changes such as macular edema can be measured objectively. The examination is suitable not only to diagnose degenerative changes in the macula, but it can also be used to diagnose glaucoma. By measuring the thickness of neurites (axons), the doctor can identify the earliest stages of glaucoma, before any changes in the visual field.
We use OCT when we want to measure corneal thickness, check the state of the cornea before the transplant or refractive interventions. Lately, OCT has been frequently used in contactology (specifying the type of contact lenses, be it ortho-K or scleral contact lenses).
OCTA (OCT angiography) is a new, non-invasive diagnostic method that registers movable contrast images of microvascular circulation (the circulatory system of the smallest blood vessels) in and around the macula. This type of scanning gives insight into the state of blood vessels by monitoring the motion of red blood cells (erythrocytes) through a network of blood vessels.
This method differs from the traditional scanning of retinal blood vessels (fluorescein angiography) because it is non-invasive and does not apply contrast.