Reproducibility of Macular Thickness Measurement Among Five OCT Instruments: Effects of Image Resolution, Image Registration, and Eye Tracking
Department of Ophthalmology & Vision Science, University of California Davis Eye Center, Sacramento, California 95817, USA. Ophthalmic Surgery Lasers and Imaging
(Impact Factor: 1.32).
01/2012; 43(2):97-108. DOI: 10.3928/15428877-20111222-02
To study the effect of image resolution, eye tracking, and image registration on central macular thickness reproducibility (rCMT) among spectral-domain and time-domain optical coherence tomography (SD-OCT and TD-OCT) instruments.
Seventy-six eyes were imaged (44 normal, 32 maculopathy) either twice using four SD-OCT and one TD-OCT devices or three times using Spectralis SD-OCT (with and without eye tracking) (Heidelberg Engineering, Inc., Heidelberg, Germany). Cirrus images (Carl Zeiss Meditec, Dublin, CA) were further analyzed with three-point image registration.
All instruments had superior rCMT in normal versus pathologic eyes (P < .001). No difference in rCMT was noted among instruments in normal eyes (P = .92), but TD-OCT was superior to SD-OCT (P = .017) in pathologic eyes. Cirrus image registration improved rCMT for normal eyes (P = .04), with borderline improvement in pathologic eyes (P = .06). Spectralis eye tracking improved rCMT in normal (P = .01) and pathologic (P = .004) eyes.
Higher image resolution with SD-OCT may not improve rCMT, but image registration and eye tracking options may improve rCMT.
Available from: Ruchire Eranga Wijesinghe
- "It is necessary to perform additional clinical experiments and collect more data from various volunteers to overcome the drawbacks of the conventional method and to improve the functioning status of the developed system. In the future, three issues will need to be addressed: (1) improving the image display rate by using dual GPU techniques ; (2) adding a fundus camera mounted on the handheld probe; and (3) improving the OCT image resolution by using eye-tracking techniques . Retinal tracking techniques have specific advantages such as removing the motion error and frame averaging to enhance contrast and remove image speckle in high-resolution images. "
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ABSTRACT: Development of a dual-display handheld optical coherence tomography (OCT) system for retina and optic-nerve-head diagnosis beyond the volunteer motion constraints is reported. The developed system is portable and easily movable, containing the compact portable OCT system that includes the handheld probe and computer. Eye posterior chambers were diagnosed using the handheld probe, and the probe could be fixed to the bench-top cradle depending on the volunteers' physical condition. The images obtained using this handheld probe were displayed in real time on the computer monitor and on a small secondary built-in monitor; the displayed images were saved using the handheld probe's built-in button. Large-scale signal-processing procedures such as k-domain linearization, fast Fourier transform (FFT), and log-scaling signal processing can be rapidly applied using graphics-processing-unit (GPU) accelerated processing rather than central-processing-unit (CPU) processing. The Labview-based system resolution is 1,024 × 512 pixels, and the frame rate is 56 frames/s, useful for real-time display. The 3D images of the posterior chambers including the retina, optic-nerve head, blood vessels, and optic nerve were composed using real-time displayed images with 500 × 500 × 500 pixel resolution. A handheld and bench-top hybrid mode with a dual-display handheld OCT was developed to overcome the drawbacks of the conventional method.
Available from: Allan A Hunter III
- "The use of image registration to identify changes more accurately in local areas of retinal thickening over time will be assessed, as will the combination of spectral-domain OCT images with other imaging modalities, such as fluorescein angiography, indocyanine green angiography, and confocal scanning laser ophthalmoscopy. Among the new generations of OCT, Spectralis OCT is equipped with image registration as well as an eye-tracking system that is able to monitor the eye position continuously using a light beam, thus increasing the reproducibility of retinal thickness measurements.28 "
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ABSTRACT: The development of spectral-domain optical coherence tomography (OCT) allows for the highest commercially available resolution of in vivo retinal anatomic details to date. The ability to see the macula with ever increasing detail is dramatically improving our understanding of the pathogenesis of retinal disease. However, the only prospective study that partially evaluated spectral-domain OCT versus time-domain OCT failed to show any clinical benefit of increased OCT resolution. Clinical outcomes, eg, best-corrected visual acuity, central macular thickness and number of injections, with "newer" OCT technologies remain an unproven advantage.
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ABSTRACT: Optical coherence tomography (OCT) is a noninvasive, noncontact imaging technique capable of producing high-resolution images of the retina and optic nerve. These images provide information that is useful for following the progression and/or resolution of posterior segment disease. Rapid advances in OCT technology allow the acquisition of increasingly detailed images, approaching the original goal of providing in vivo histopathology. Increases in scan acquisition speeds and axial resolution enhance the clinical diagnostic value of this modality. Adapting instrumentation designed for use in human patients for use in animals can be challenging. Each species has a unique set of adjustments that need to be made but it is possible to obtain reproducible, high-quality OCT images in a variety of animals, including rodents, dogs, cats, pigs, and monkeys. Deriving quantitative measurements from OCT instruments is hindered by software algorithm errors in detecting the edges of the distinct retinal layers. These segmentation errors occur in scans of human eyes as well in other species and arise with similar frequency with each of the different OCT instruments. Manual segmentation methods to derive optic nerve head and other structural indices have been developed for several species.
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