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With the advent of intravitreal agents that block the negative effects of vascular endothelial growth factor among patients with age-related macular degeneration, ophthalmologists have begun to seek a higher level of performance from our diagnostic equipment.
Tracking patient response to these new treatments and assessing the need for re-treatment require highly precise measurements, not just of the qualitative nature of macular and retinal thickness, but their quantitative nature as well. More than ever, small changes must be charted accurately over a long period.
Optical coherence tomography (OCT) has played a crucial role in these efforts so far. This non-invasive imaging technique affords a high-resolution assessment of retinal thickness largely unmatched among rival diagnostic systems. In addition to its value in retinal disease, OCT has proven useful at assessing glaucoma via its telltale patterns of retinal nerve fiber layer (RNFL) degeneration.
Despite its success and increasing popularity, OCT remains subject to computer- and user-generated errors that can jeopardize the accuracy of results.1,2 Manufacturers have taken steps to improve OCT's performance and resolution, the most well known probably being the introduction of Fourier-domain scanning.
A recent addition to next-generation technology is the new software (FastMap) for a spectral-domain OCT system (3D OCT- 2000, Topcon Medical Systems Inc.). Having had experience with it in clinical settings, the authors discuss some details regarding the new software.
Unveiled in the fall of 2008, FastMap is the upgraded version of the TrueMap software package included with Topcon's Fourier-domain OCT systems. This technology allows for chronological assessment of the same area of the retina over a long period.
Users can choose from among 3D scan, 2D b-scan, fundus image, or retinal thickness map settings. As of this writing, the Topcon 3D OCT 2000 is the only OCT machine on the market that offers fundus photography.
Increased speed is the most noticeable improvement of the new software. An image captured on FastMap becomes immediately available on any remote viewing station. In addition, faster image capture reduces the time during which a patient's eye can move, thus increasing the prospect of obtaining a high-quality scan rapidly.
Method and system
Another enhanced feature is the synchronized playback option. This allows the user to place two separate OCT images taken at different times adjacent to each other on screen. The practitioner can then scroll through the images simultaneously, one frame at a time, scrutinizing the data for small, subtle changes. Essentially this feature amounts to a 2D, synchronized b-scan.
Synchronized playback offers a clinical benefit to patients with macular degeneration, allowing localized areas to be tracked for disease progression. The comparison images do an exceptional job of delineating macular edema and sub-retinal fluid.
Physicians also might employ this feature for managing vitreomacular traction syndrome or edema secondary to a retinal vein occlusion.