✍️ Posterior segment evaluation with OCT allows visualization of the vitreous, retinal layers, retinal pigment epithelium (RPE) and the choroidal layers.
OCT basics ( Vitreous )
✍️ The posterior hyaloid of the vitreous can be identified on macula scans especially with spectral-domain (SD-OCT).
✍️ useful in the evaluation of posterior vitreous detachments, vitreomacular traction or vitreopapillary traction.
✍️ The instrument uses 840nm wavelength of light ( can’t penetrate denser vitreous opacities like Weiss rings or asteroid hyalosis).
OCT basics ( Retina )
✍️ The inner retinal layers show atrophy secondary to retinal vascular occlusions like retinal artery occlusions.
✍️ The outer retinal layers show atrophy secondary to conditions that affect the RPE ( AMD and CSR)
✍️ Four distinct hyperreflective lines are seen in the outer retinal layers of a SD-OCT scan on a healthy eye.
✍️ Each distinct retinal layer is visible on the OCT and corresponds well to histological studies.
✍️ Certain types of retinal conditions can affect different retinal layers.
✍️ The retinal nerve fiber layer and retinal ganglion cell layer are affected in conditions like glaucoma.
distinct hyperreflective lines are seen in the outer retinal layers of a SD-OCT scan on a healthy eye.
✍️ These four hyper-reflective lines should always be identified when evaluating a macula scan.
☝️ RPE (retinal pigment epithelium)
☝️ COST(cones outer segment tips line or IZ- interdigitation zone )
☝️ EPIS (ellipsoid portion of the inner segments or EZ- ellipsoid zone or IS/OS- inner segment outer segment junction line)
☝️ ELM(external limiting membrane)
OCT basics ( Choroid )
✍️ The choroid can be visualized by enhanced-depth imaging (EDI) or imaging with longer wave-length OCT
✍️ Certain conditions that affect the choroid have been found to have an abnormally thicker choroid.
✍️ in CSR and PCV , the choroidal thickness is thicker with visible large dilated choroidal vessels compared to age-matched normals.