Inflammation as a general rule increases the optical reflectivity from within affected tissue because the migration of inflammatory cells into the retina or vitreous increases the concentration of optical scatterers. OCT can provide dynamic images of the inflammatory process, localizing the infiltrate to specific retinal layers and providing a means to track the extent of inflammation following treatment. The intensity and size of the lesion correlate with the density and extent of the infiltrate, respectively, OCT is also useful in evaluating morphological changes secondary to acute or chronic inflammation, such as retinal edema, fibrosis, and atrophv.
Vision loss due to uveitis is commonly caused by macular edema which may be quantitatively assessed as retinal thickening on the OCT tomogram. Serial follow-up OCT images through the fovea allow the accurate evaluation of macular fluid accumulation and provide an objective means of assessing the efficacy of pharmacological treatment [I].
Many ocular diseases cause chorioretinal inflammation [21, OC provides an effective means of quantifying the reflectivity, location, and extent of these inflammatory lesions in cross-section. The typical
' punched-out" lesion found in the presumed ocular histoplasmosis syndrome  appears on OCT as a focal region of elevated reflectivity in the deeper choroid. Choroidal neovascularization in this disease can also be diagnosed and localized by a disruption and fragmentation of the reflective band corresponding to the retinal pigment epithelium and choriocapiilaris on the OCT images.
In contrast, acute toxoplasmosis retinitis 14] or cytomegalovirus lesions  exhibit enhanced backscat-ter due to inflammation primarily affecting the neurosensory retina. Chronic lesions progress to retinal atrophy and fibrosis, which are evident on OCT as increased retinal reflectivity, marked retinal thinning, and increased penetration of the probe light into the choroid.
HIV retinopathy  is often manifested by cotton wool spots, probably associated with focal ischemic injury and swollen nerve fiber axons. OCT images demonstrate a corresponding lesion displaying enhanced reflectivity from only the inner retinal layers. In contrast, diseases such as progressive outer retinal necrosis [61 show lesions developing in the outer retinal layers,
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