OPTICAL COHERENCE TOMOGRAPHY PDF
There have been three basic approaches to optical tomography since the early s: diffraction tomography, diffuse optical tomography and optical coherence . PDF | Optical coherence tomography is a quick, non invasive and reproducible imaging tool for macular lesions and has become an essential part of retina. Abstract Optical coherence tomography (OCT) is a non-invasive imaging technique providing real-time two- and three-dimensional images of.
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Optical Coherence Tomography. • Analogous to ultrasound, except that it measures intensity of back-reflected light. • Technologically different than ultrasound. Optical coherence tomography is a micrometer-scale imaging modality that permits label-free, cross-sectional imaging of biological. Optical Coherence Tomography (OCT) and opened new horizons in several areas of Optical coherence tomography of a hand palm, the letters indentifies the.
This diminishes the chance of inadvertently missing pathology. Uses Retina OCT showing both macular edema and subretinal fluid in a diabetic patient OCT is useful in the diagnosis of many retinal conditions, especially when the media is clear. In general, lesions in the macula are easier to image than lesions in the mid and far periphery. OCT can be particularly helpful in diagnosing: Macular hole Vitreomacular traction Macular edema Detachments of the neurosensory retina and retinal pigment epithelium e.
Yet, in other disorders, especially retinal vascular disorders, it may be helpful to order additional tests e.
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Optic neuropathies OCT is gaining increasing popularity when evaluating optic nerve disorders such as glaucoma. OCT can accurately and reproducibly evaluate the nerve fiber layer thickness.
This higher wavelength light results in greater absorption and less penetration. In this fashion, images of the anterior segment cornea, anterior chamber, iris and angle can be visualized. Limitations Because OCT utilizes light waves unlike ultrasound which uses sound waves media opacities can interfere with optimal imaging.
As a result, the OCT will be limited the setting of vitreous hemorrhage, dense cataract or corneal opacities. Akinetik Swept Sources. FDML incl. Fabrice Harms, Anne Latrive, A.
Optical Coherence Tomography : Newer Techniques , Newer Machines
Claude Boccara. Digital Holoscopy. Optical Coherence Microscopy. Aaron D. Ahsen, James G. OCM with Engineered Wavefront. Rainer A. Leitgeb, Theo Lasser, Martin Villiger. Holographic Optical Coherence Imaging. David D.
Steven G. Adie, Nathan D. Shemonski, Tyler S. Ralston, P. Scott Carney, Stephen A. Optical Coherence Elastography. Brendan F.
Kennedy, Kelsey M. Kennedy, Amy L. Oldenburg, Steven G. Adie, Stephen A. Boppart, David D. Polarization Sensitive Optical Coherence Tomography. Christoph K. The reflectivity of the content of the cysts as well as the size of the cysts is believed to have prognostic value. OCT can detect macular edema that is not clinically evident, and several OCT-derived biomarkers are useful predictors of progression, severity, and visual outcome.
Figure a Spectral domain optical coherence tomography of a patient with an epiretinal membrane and diffuse diabetic macular edema. Diffuse thickening of the Henle's layer is seen, with intraretinal hyper reflective deposits yellow arrow.
The presence of intra or SRF is an indication of activity that requires treatment. RPE detachments alone may not indicate the need for treatment. Cystoid changes can also be present over long-standing fibrotic lesions. The main role of OCT is to identify small changes in activity to determine the need to initiate, continue, stop, or switch treatment for CNV.
A higher incidence of serous retinal detachment is present in the acute phase and more of cystoid changes later. With increasing chronicity, schitic spaces may develop. In CME, it predominantly involves the inner nuclear and outer plexiform layers.
Optical coherence tomography
Retinoschisis in optic pit The schisis is seen to extend till the optic disc margin and involves the outer plexiform layer. The optic pit can be seen on OCT with a vitreous tuft that may be associated. However, the most common associated finding is serous retinal detachment with outer lamellar holes. Additional cystic changes may be seen in the inner layers. These changes are seen to reverse with the occurrence of PVD which could be spontaneous or surgical. However, VMT is typically absent.
This can be seen in the inner, middle, or outer retinal layers with combinations of the same.
Associated features in myopic eyes are ILM detachment, ERMs, retinal microfolds, ellipsoid zone defects, paravascularmicroholes and macular holes, dome-shaped macula, and peripapillary intrachoroidal cavitations. Figure a Swept-source optical coherence tomography of a myopic staphyloma showing schisis in the inner and outer retinal layers yellow triangle , as well as an outer retinal hole yellow arrow. They are believed to represent degenerating photoreceptors and signify advanced disease. On cursory glance, they may appear as cystoid spaces, prompting unnecessary intervention as they have been shown to remain unchanged with treatment.
However, the correlation between central retinal thickness and best-corrected visual acuity BCVA is seen to vary between conditions. The detached retina shows elongated photoreceptor segments which are a feature of most acute cases. The subretinal space may show moderate or highly reflective homogenous areas suggestive of fibrin with characteristic areas of clearing within them.
The area of active leak may be seen either as a PED with a microrip, an area of RPE elevation or may be indicated by a sagging of the posterior layers of the detached retina toward an area of RPE elevation or detachment. Other features described include thinning of the inner choroidal vessels, focal choroidal excavation  ,  ,  defined as a macular lesion with choroidal excavation detected on SD-OCT without evidence of scleral ectasia or posterior staphyloma , and loculation of fluid in the posterior choroid.
Figure a Central serous chorioretinopathy with neurosensory RD, low-reflective subretinal deposits blue star , and dilated large choroidal vessels yellow star. Both eyes show intraretinal cystoid spaces yellow triangle , shallow subretinal fluid blue star , irregular retinal pigment epithelium elevation and dilated large choroidal vessels yellow star , retinal pigment epithelium rip in the right eye yellow arrow and two serous pigment epithelial detachments red arrows in the left Click here to view Optical coherence tomography in Vogt-Koyanagi-Harada versus central serous chorioretinopathy Common features are serous macular detachments and choroidal thickening.
Features more suggestive of Vogt-Koyanagi-Harada VKH are subretinal septae, multiple pockets of SRF, RPE undulations, ILM irregularities and loss of reflectivity in the inner choroid, gross choroidal thickening with inability to visualize the choroidoscleral junction. Figure a Drusenoid pigment epithelial detachment in age-related macular degeneration with homogenous content yellow star and soft drusen red arrow.
Intraretinal hyperreflective dots are seen yellow arrow. Moderately reflective subretinal pigment epithelium vascular structures yellow arrow and subretinal fluid blue star. They are seen as high reflective smooth or undulating elevations of the RPE. The sub RPE material is dense, homogeneous and of moderate to high reflectivity.
Hyper reflective foci above the RPE indicate pigmentation.Additionally the dispersive elements in the spectroscopic detector usually do not distribute the light equally spaced in frequency on the detector, but mostly have an inverse dependence. The overall market is estimated at more than 0. These represent areas of photoreceptor destruction and are irreversible.
Ralston, Daniel L. Reference work. The advantages of SS-OCT technology are higher imaging speed; higher detection efficiencies, improved imaging range, and reduced sensitivity roll off with increasing depth.
Choroidal thickness measurements are possible with the advent of enhanced depth imaging and SS imaging.