Spotlight ON TECHNOLOGY & TECHNIQUE

The Cirrus Model 400: Making Spectral-Domain OCT Affordable

By Leslie Goldberg, Associate Editor

An estimated 37,000 OCT scans are taken daily in the United States for diagnostic purposes in ophthalmology. With the availability of OCT, many general ophthalmologists say they are now able to pick up macular problems earlier in treatment, spot CME preoperatively rather than postoperatively, and diagnose and treat less serious retinal issues.

Cutting-edge spectral-domain OCT technology offers greater imaging sophistication than time-domain OCT. For price-conscious practices, the Cirrus Model 400 from Carl Zeiss Meditec may be the ideal solution to obtaining an SD-OCT. This model has the same integrated design as the Cirrus Model 4000, with core OCT functionality for retina, glaucoma and anterior segment, but uses Live OCT Fundus technology to capture fundus images, while Model 4000 uses a line scanning ophthalmoscope (LSO).

The Cirrus 400 (above) uses the same modern integrated design and small footprint as the 4000.

The 4000 Model Versus the 400

The Cirrus HD-OCT Model 4000 provides a live fundus image using a line scanning ophthalmoscope to guide the placement of OCT scans. In 2009, Carl Zeiss Meditec engineers developed a novel method to generate the fundus image without the use of this additional hardware.

Here's how it works. The Cirrus HD-OCT uses LSO scan data to present a live fundus image. An operator can move the OCT cube within the fundus image before acquisition. After the OCT cube scan is acquired, an en-face OCT cube scan image is reconstructed and overlaid on the LSO live fundus image to indicate the position of OCT cube scan.

In the Cirrus HD-OCT Model 400, a novel approach is used to quickly capture the OCT cube scan and generate the en-face OCT fundus image continuously. The standard view of the Live OCT fundus image refreshes approximately once per second. Once the operator clicks the “Capture” button, acquisition of the Live OCT fundus image is completed and then the high-definition cube scan is acquired. The result is a background fundus image and full cube scan superimposed on the fundus image. Similarly, for the five-line raster pattern, the raster lines are superimposed on the OCT fundus image.

The high-definition cube and the five-line raster data that are collected are identical on both the Model 4000 and Model 400. As a result, the data are interchangeable and the same analysis can be performed on both models.

The one exception is a new Enhanced HD raster scan, which provides an even higher quality image than previously available. This feature is only available on the Model 4000. Future features dependent on the LSO fundus will be available only for the Model 4000.

“We were ready to get a new OCT instrument, so of course we looked at spectral domain,” says Scott Massios, MD, in private practice in Seneca, SC. “We tested both the Cirrus HD-OCT 400 and 4000 models and were impressed with the capabilities and acquisition times of both. Clinically, I found that the Model 400 provided the features that we need in my practice. The 400 is easy to use, just like the Model 4000, and the data-acquisition technology is identical to the Model 4000 but at a lower price.” OM

To learn more about the Cirrus 400, visit www.meditec.zeiss.com.