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Editors Selection IGR 7-3

Blood Flow: Vascular imaging with 1 micron OCT

Comment by Joel Schuman on:

23963 Wide-field optical coherence tomography of the choroid in vivo, Povazay B; Hermann B; Hofer B et al., Investigative Ophthalmology and Visual Science, 2009; 50: 1856-1863

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Povazay et al. (695) explore the use of one micron optical coherence tomography (OCT) for retinal, choroidal and vascular imaging. They demonstrate isotropic scanning of the retina, choroid and chorio-scleral junction with mathematical postprocessing suppression of motion artifacts of up to 38 degrees, and show images from tissue cubes sampled at 512 x 512 x 512 voxels in 1.5 x 1.5 x 0.5 mm3 three-dimensional datasets. As expected, they show better tissue penetration at 1060 nm than 800 nm. This group continues to be highly productive and innovative in their approach to ophthalmic imaging, especially in the use of longer wavelength light sources to achieve greater penetration depth with decreased scattering. The techniques demonstrated in this article have the potential to enable new diagnostic methods and targets for detection of glaucoma and measurement of its progression. Structures such as the layers of the intraretinal vasculature, choroid and lamina cribrosa are now accessible using approaches described by this group and by others. It is possible that these structures, either independently or in concert with tissues assessed using conventional OCT, would provide more sensitive and specific assessment of the disease.

A caveat to the clinician is that the technology used in Povazay et al.'s work is complex and expensive; however, it is likely that costs will fall and complexity will decrease with potential future commercialization of one micron light source OCT systems. Additionally, scan densities described in this work are high and time consuming despite rapid imaging. The image processing algorithms used for the correction of the various types of motion artifact resulting from lengthy scan times are susceptible to failure and may not reproduce three-dimensional structure accurately every time. The imaging procedure itself may fail as well, as the authors report inability to obtain three dimensional choroidal imaging in 30% of eyes studied. Finally, while the images in this work are impressive, it is possible that the C-mode images could be further improved to accurately represent individual tissue layers, allowing even higher quality tissue mapping using one micron high speed OCT imaging.
The authors are to be commended for a work demonstrating increased potential for clinical imaging with rapid non-invasive assessment of existing and new diagnostic targets.

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