Advances in spectral domain 3-D high-resolution OCT

Spectral domain optical coherence tomography (SD-OCT), the latest generation of the technology, is abreakthrough because it has dramatically cut the time required to obtain images by eliminating themoving mirror that was a component of standard OCT, according to Cynthia Toth, MD.

In addition to being 50 times faster than conventional OCT, SD-OCT has improved resolution because ofimproved processing. Another benefit is decreased patient movement artifact, especially in pediatricpatients.

"In age-related macular degeneration, there is often motion artifact. It is difficult to sort outdrusen and differentiate them from patient motion that could be either or a pigment epithelial defector normal retinal pigment epithelium (RPE) choroid. Using SD OCT it is easier to isolate drusen fromthe underlying baseline RPE and to define whether pigment epithelial detachments or RPE abnormalitiesare present," Dr. Toth stated. She is professor of ophthalmology, Duke University Medical Center,Durham, NC.

The SD-OCT data can be integrated with the information obtained from angiography and fundusexaminations, which allows identification of the location of an abnormality found on OCT."One benefit of SD-OCT is the creation of the summed voxel projection (SVP), which is helpful fororientation of individual OCT scans. One can collapse 3-D OCT volumes along the depth axis to form a2-D plane, summing pixels to calculate one representative pixel intensity along each line in theprojection," she explained. As a result of prominent shadowing from the retinal vasculature, the SVPimage is similar to a fundus photograph and this image can be used to orient the SD-OCT image to afundus image.

Drawbacks of the technology include large datasets, the need to integrate data with conventionalimaging, and normative data are required for the new systems, there are a number of systems fromwhich to choose. An advantage is the availability of portable systems.

"Three-dimensional SD-OCT offers the potential to identify biomarkers and measure changes in diseaseover time. For clinical and research use, improved methods are needed to export, analyze, summarize,and manage data. These are on the way," Dr. Toth concluded.