![]() The Stratus OCT system corrects for this effect by extrapolating across areas not sampled but, depending on the nature of the macular anatomy in those areas, quantitative differences in macular thickness computations may arise between the OCT systems. The Stratus OCT employs fewer A-scans, and these are more heavily weighted toward the center of the scan. In the Cirrus HD-OCT system, significantly more A-scans are used, and these are evenly distributed over the scanned area. This array differs between the Stratus OCT and Cirrus HD-OCT systems. Data for thickness calculations are collected from an array of A-scans distributed across the macula. STRATUS OPTICAL COHERENCE TOMOGRAPHY SOFTWAREAlthough both time domain and spectral domain OCT use the same basic working principles, the scan rate of spectral domain OCT is at least 20,000 axial scans per second, with an improved axial resolution of 5 μm.īoth the Stratus OCT and the Cirrus HD-OCT systems employ intrinsic software algorithms to calculate retinal thicknesses averaged across standardized subfields in the macula. One such instrument that is currently commercially available is the Cirrus HD-OCT (Carl Zeiss Meditec, Inc.). Recently, a new class of OCT instruments employing spectral (Fourier) domain technology has been developed. 6 - 9 This instrument acquires images at a rate of 400 axial scans per second, with an axial resolution of 10 μm. To date, time domain OCT using the Stratus OCT (Carl Zeiss Meditec, Inc., Dublin, CA) has been the most widely used technique for obtaining macular measurements 1 - 5 and has been shown in previous studies to generate measurements with high repeatability. Automated measurements of retinal thickness and volume in the macula from retinal tomograms using image-processing software have been useful in observing patients longitudinally in clinical practice and making comparisons in clinical trials. Optical coherence tomography (OCT) evaluation of macular structure is important in the diagnosis and monitoring of patients with diabetic macular edema (DME). ![]()
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