SD-OCT Races Forward
Sneak Preview of the Premiere issue
SD-OCT Races Forward
Get up to speed on the latest advances in spectral domain OCT technology.
Beginning with our premiere issue, diagnostic technology is a section that will appear in each issue of Ophthalmic Professional.
One of the fascinating developments in recent years is the technological leap made by ocular coherence tomography (OCT) systems. This non-contact transpupillary imaging technology originally provided imaging of retinal structures. (See the sidebar "An Introduction to SD-OCT," below.) Today's spectral domain OCT (SD-OCT) systems not only provide higher resolution of the posterior segment at much faster speeds than previous time domain (TD-OCT) systems, they also offer a number of features including three-dimensional mapping, cross-sectional imaging and anterior segment imaging. One of the most interesting new applications of the technology is intraoperative OCT, which was recently described in our sister publication, Retinal Physician:
While it would take an expansive article to present all the latest features of each manufacturer's SD-OCT system, we offer a sampling below. (For complete technical information and updated specifications, we recommend you contact the manufacturer.)
While intended primarily for imaging retinal tissue, with a switch of focus this company's SD-OCT system can be used to capture images of the cornea, sclera, and conjunctiva, according to Bioptigen's website.
The system may interest both researchers and clinicians as it allows either to resolve the retina's microstructure in fine detail. The structural details that can be elucidated include the retinal nerve fiber layer, the inner and outer plexiform and nuclear layers, the retinal pigment epithelium, and choroidal vessels.
Heidelberg Engineering (http://www.heidelbergengineering.com/us/)
Heidelberg received FDA clearance in March, 2011, for its Spectralis OCT anterior segment module. The upgrade reportedly provides high-resolution images of the cornea, anterior chamber angle, and sclera. Clinicians can assess both angles at once using a 16 mm-wide angle-to-angle OCT scan.
Heidelberg's Spectralis integrates spectral-domain OCT with confocal scanning laser ophthalmoscopy. The two technologies enable new imaging capabilities, such as an eye-tracking function as well as blue laser autofluorescence.
Carl Zeiss Meditec (www.carlzeissmeditec.com)
Zeiss's new Cirrus OCT software version 6.0 provides cross-sectional images and maps showing details of retinal changes otherwise difficult to spot. In addition, quantitative analysis of retinal features facilitates not only the initial diagnosis, but also ongoing monitoring or treatment. Scans produce opportunities to analyze the retinal nerve fiber layer, optic nerve head, and macular thickness at the present moment and serially from there.
Specifically, the new software features advanced RPE analysis (model 4000 only) ganglion cell analysis, Enhanced GPA (Guided Progression Analysis) with ONH (optic nerve head) Change Analysis.
Optovue's OCT systems now offer the flexibility of paying on a per-use basis, which can minimize the up-front costs. Its new RTVue XR system features a 70,000 A-scan per second camera, reportedly nearly three times faster than some other systems. The RTVue's eye-tracking software yields precise image detail with a retinal scanning depth of nearly 3 mm.
The RTVue's capacity to measure corneal powers for IOL calculations is also worth mentioning. Perhaps the greatest benefit in this case is for post-refractive patients with altered corneal curvatures. The RTVue measures both the cornea's front and back surfaces. The company's iVue OCT system, meanwhile, offers a lower-priced, portable alternative often used for screening purposes.
Topcon Medical Systems (www.topconmedical.com)
Topcon's 3D OCT-2000 system—with its reportedly user-friendly and easily navigable color touch screen display and compact footprint—incorporates a high-resolution fundus camera. Topcon's software allows dynamic viewing of two- and three-dimensional fundus images at once.
Three-dimensional imaging may enhance a clinician's understanding of complex pathologies such as vitreous traction, macular edema, and retinoschisis, according to Topcon's website. The built-in fundus camera, meanwhile, allows you to inspect conditions that might be missed on OCT such as disc hemorrhages. Topcon's software is said to use 3D registration technology to reduce artifacts caused by eye movement.
The company's thickness-measurement function includes both overall retinal thickness and the retinal nerve fiber layer. A mosaic-type image display reportedly creates panoramic views from the macula to the optic disc.
Portions of this article were adapted from "A Winning Combination," which appeared in the July issue of
An Introduction to SD-OCT
In addition to SD-OCT manufacturer websites, there are a number of resources that provide an introduction to this SD-OCT technology. Here are links to several articles from our sister publications Retinal Physician and Ophthalmology Management that describe SD-OCT:
Ophthalmic Professional, Issue: August 2012