The software also locates the OCT line scan in the fundus photo for easy comparison between imaging modalities. 5 The software provides the clinician with same-time image viewing of the fundus photo and OCT. The 3D OCT-2000 uses a high resolution, 16.2 megapixel fundus camera as well as a color touchscreen. 3 An upcoming software algorithm is expected to add a widefield analysis of the posterior pole, including the optic nerve head (ONH), RNFL and ganglion cell analysis (GCA), in one printout. The Cirrus HD-OCT’s current software features additional layouts that enable the clinician to see nerve and macular findings on a single printout and formulate functional and structural relationships between visual fields and OCT data, respectively. IR, blue laser FAF, red-free photos, FA, ICG angiography, panning camera SD-OCT, confocal scanning laser ophthalmoscope (cSLO) Comparison of Imaging Modes and Capabilities by Model Current models allow image acquisition with miotic pupils, which is advantageous for patients who struggle with dilation due to age or other factors. Two more benefits of new OCT software are 3D reconstruction of the retinal image and structural comparison functions, which compare a lesion within an area of the OCT image to the associated location visible on a retinal photograph. OCT’s ability to define particular layers of the retina, known as “segmentation,” as well as depth localization in tissue, also aids in identifying points of interest within the scans. These models also have increased fundus camera resolution and focus options for detailed image capture compared with prior TD-OCT ( Table 2). With eye tracking capability and image registration, artifacts are much less common than in prior technology. 3,4 The increased speed and resolution provide an enhanced ability to visualize retinal layers. Today’s SD-OCT can also provide an axial resolution of 3µm to 6µm within tissues, compared with previous TD-OCT technology, which had a maximum resolution of 10µm. 1,2 This improvement is beneficial to the clinician because it minimizes image artifacts, makes 3D imaging possible and increases image resolution. While the earliest time-domain (TD) OCT technology could only acquire 400 scans per second, current SD-OCT models, depending on the manufacturer, can capture between 26,000 and 70,000 axial-scans per second ( Table 1 ). *Cirrus OCT (5000 model with version 6.5 software) acquires 68,000 scans per second with fundus photos Spectralis SD-OCT (Heidelberg Engineering) 6 Comparison of Four Commercially Available SD-OCT ModelsĬirrus HD-OCT 5000 (Carl Zeiss Meditec) 2
#Ocular coherence tomography how to
This article outlines the basics of OCT imaging and walks you through how to analyze retinal nerve fiber layer (RNFL) thickness, macular thickness and ganglion cell complex using each model. The technological growth in ocular imaging has allowed for profound advancements in the clinician’s ability to recognize subtle abnormalities, differentiate stability from progression in ocular pathology and identify disease stages.Ĭlinicians have four prominent commercially available spectral-domain (SD) OCT models to choose from: Spectralis SD-OCT (Heidelberg Engineering), 3D OCT-2000 (Topcon Medical Systems), Avanti RTVue XR (Optovue), and Cirrus HD SD-OCT 5000 (Carl Zeiss Meditec). Optical coherence tomography (OCT) has evolved over the last several years from a device used in only a few practices to one found in many primary eye care clinics.
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