Mox

Figure 2-9. OCT tomogram acquired through fixation of a patient with cvstoid macular edema secondary to non-proliferative diabetic retinopathy. The retina is significantly thickened, with loss of the normal foveal pit contour. Intraretinal fluid accumulation leads to the development of non-reflective cystic spaces and reduced reflectivity from the neurosensory retina. Focal areas of high backscattering which shadow the retinal layers below correspond to hard exudate.

Figure 2-9. OCT tomogram acquired through fixation of a patient with cvstoid macular edema secondary to non-proliferative diabetic retinopathy. The retina is significantly thickened, with loss of the normal foveal pit contour. Intraretinal fluid accumulation leads to the development of non-reflective cystic spaces and reduced reflectivity from the neurosensory retina. Focal areas of high backscattering which shadow the retinal layers below correspond to hard exudate.

paring nerve fiber thickness through different planes and in assessing the profile of the optic disc. The location of each tomogram on the retina is labeled on a corresponding fundus photograph. In the 90û tomogram (taken perpendicular to the papillomacular axis), high backscattering (red) is visible from the NFL and from a band defining the posterior boundary of the sensory retina, corresponding to the RPE and cho-riocapillaris. The tomogram shows the NFL expanding towards the optic disc to occupy nearly the entire retinal thickness, commensurate with the presence of the inferior and superior arcuate nerve fiber bundles, In comparison, the 0° tomogram (taken parallel to the papillomacular axis) exhibits a thinner NFL, consistent with fewer nerve fibers in this area. The surface contour and normal cupping of the disc are visualized in all of the tomograms. The termination of the choroid at the lamina cribosa is also delineated.

Circular Tomograms in the Peripapillary Region

Documentation of nerve fiber laver thickness and j degeneration in the peripapillary region may be important in the diagnosis and treatment of glaucoma and other neurodegenerative diseases. A useful way of assessing the NFL in this area is to image cylindrical tissue sections centered around the optic disc. Figure 2-8 shows two circular OCT tomograms with dif ferent diameters, each centered on the nerve head. Each tomogram is displayed unwrapped and corresponds to a clockwise scan around the optic disc. The location and orientation of both tomograms on the fundus also depicted.

The anterior and posterior highly backscattering layers represent the NFL and choriocapillaris/RPE, respectively. The inferotemporal and superotemporal nerve fiber bundles are evident in both tomograms as localized thickenings in both the NFL and retina. The bundling becomes more diffuse in the images as the distance from the optic nerve head increases with a larger scan diameter, as expected from normal anatomy.

Was this article helpful?

0 0

Post a comment