![]() ![]() 8,9Ĭurrently, EDI scans are available on the 40 Zeiss models as well as the second and third generation Spectralis models. 1 The EDI feature has become the gold standard of detection of optic nerve head drusen and very useful in age-related choroidal atrophy, high myopia, central serous chorioretinopathy and choroidal tumors. 7 EDI-OCT penetrates an additional 500µm to 800µm deeper compared with traditional OCT. Two commercially available SS-OCTs today are Topcon’s Triton DRI ( Figure H) and Plex Elite 9000. 2,3 With these parameters, SS-OCT allows for penetrance to the level of the choroid with a reduced axial resolution. 840nm in SD-OCT) to overcome scattering light defects of the RPE and faster scanning times (100,000 to 400,000 A-scans/sec) allow for longer B-scans to help with widefield imaging. 5 SS-OCT uses longer wavelengths (1050nm vs. SS-OCT and EDI-OCT allow for deeper retinal imaging that includes the choroid, with faster acquisition speeds. 4 Furthermore, advancements and upgrades in OCT systems include widefield, swept-source, enhanced-depth imaging (EDI-OCT) and OCT angiography (OCT-A) technologies. Most continue to allow image acquisition with miotic pupils, which is advantageous for patients who struggle with dilation due to age or other factors. Many of the newer SD-OCTs have more anterior segment options to better evaluate the cornea and anterior chamber ( Figures I to L). Multimodal imaging offers full-color, high-resolution fundus photography, reflectance imaging and fundus autofluorescence. These SD-OCT devices have enhanced fundus camera capabilities, increased field of view and can combine retinal nerve fiber layer (RNFL), macula and ganglion cell layer (GCL) all in one report ( Figures A and B). ![]() Today, the most common OCT models on the market for eye care are the combination OCT/fundus systems and advanced OCT models. 2Ĭommon OCT abbreviations and terminology. ![]() 3 This development allows the clinician to minimize motion artifacts and provides volumetric analysis with three-dimensional imaging capabilities to obtain better quality images. 2Ĭurrent spectral-domain OCT (SD-OCT) offers a superior resolution with a lessened acquisition time and can capture between 26,000 and 80,000 axial scans per second, while swept-source OCT (SS-OCT) can achieve upwards of 100,000 to 200,000 axial scans per second ( Tables 1 and 2). It could only acquire 400 scans per second with an 840nm wavelength, which limited imaging resolution and sampling density. Now considered primitive, the original time-domain analysis used an infrared light source and was dependent on movement of a mirror to change the optical path of a reference beam. Since its 1991 debut, OCT technology has continually evolved. This article outlines the basics of OCT imaging, the newest model updates, a guided data analysis of the different instruments’ metrics and how to interpret various measurements using each model. For this article, four prominent ones will be described: Cirrus HD SD-OCT 5000 (Carl Zeiss Meditec), 3D OCT-1 Maestro2 (Topcon Healthcare), Spectralis SD-OCT (Heidelberg Engineering) and Optovue iVue80 (Visionix). These now-multimodal imaging devices can help aid in the diagnosis of both ocular and systemic disease.Ĭlinicians have several commercially available spectral-domain (SD) OCT models to choose from. With the increase in clinical implementation to manage ocular and systemic disease, optometrists must continue learning how to expand the technology’s uses from conventional and common to sophisticated but practical. This technology offers a noninvasive approach of imaging ocular tissues with high resolution by measuring back-scattered light and producing a cross-section topographic image. The principles of optical coherence tomography (OCT) were first described just over 30 years ago and the first commercial device came on the market in 1996.
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