OCT can non-invasively document changes in single retina layer thickness and structure due to neuronal and retinal glial cells (RGC) modifications in systemic and local inflammatory and neurodegenerative diseases. Spectral domain optical coherence tomography (OCT) allows for detailed evaluation of the retina and the optic nerve. The retina and the optic nerve are considered extensions of the central nervous system (CNS) and thus can serve as the window for evaluation of CNS disorders. This layer is separated from the choroid by the Bruch membrane The tenth layer houses the retinal pigment epithelium cells. The ninth layer, the photoreceptor layer (PR) contains the cones and rods. The eighth layer, the external limiting membrane (ELM) is formed by the union between the Müller cells with each other and with the photoreceptor cells. The seventh layer, the outer nuclear layer (ONL) contains the nucleus of photoreceptor cells. The sixth layer is the outer plexiform layer (OPL) where photoreceptor cells, bipolar cells and horizontal cells interact. The fifth layer, the inner nuclear layer (INL), contains the nucleus of bipolar, horizontal, amacrine and Müller cells. The fourth layer is the inner plexiform layer (IPL) where bipolar, amacrine and ganglion cells interact.
The third layer is the ganglion cell layer (GCL) mainly composed of the nucleus of the ganglion cells. The second layer, the retinal nerve fiber layer (RNFL) contains axons of ganglion cells and retinal vessels. The first layer, the internal limiting membrane (ILM) is formed by the endfeet of the Müller cells. Retina is formed by 10 layers from the inner to the outer part of the retina.