The technology and advanced features found in OCT instruments are becoming an asset in the overall picture of diagnosis, management, and treatment of glaucoma.
While diagnosing and managing glaucoma has become a part of an optometrist’s daily practice, optical coherence tomography (OCT) has elevated our level of care in doing so. By providing cross-sectional views of the retinal nerve fiber layer (RNFL), macula, optic nerve, and even the anterior segment, practitioners can more accurately track and manage patients over time. Advanced 3D images offer an entirely new way to view ocular structures.
“I believe OCT is the most valuable instrument that has been brought to eyecare in the last 30 years,” says J. James Thimons, OD, of Darien, CT. “I don’t think anything exceeds it in the impact it can create in diagnostic capability and the change in the quality of care that you render to your patients.”
Here are a couple of OCT systems that offer technology which can have a dramatic impact on a practitioner’s level of care. (For a quick listing of OCT systems, see “OCTs At-A-Glance.” )
For many practices, the Stratus OCT™ by Carl Zeiss Meditec, Inc. has become the standard of glaucoma care. Featuring real-time cross-sectional images and quantitative analysis software, assessing the early signs and changes of glaucoma is easy and accurate.
Included with the Stratus OCT are different analysis tools. The RNFL is a series of 3.4mm circular scans around the optic nerve head to capture the measurement of the peripapillary layer. These measurements are compared to a normative database, the amount of asymmetry is calculated, and a serial analysis is performed.
Optic Nerve Head analysis is a series of radial line scans made through the optic disc to capture data, including cross-sectional and topographical maps. Key features of this data include cup-to-disc ratios and horizontal rim volume, both of which can be tracked and followed over time. The Macular Thickness Analysis with radial line scans show macular thickness, retinal layers, and macular condition.
The Optic Nerve Head Report includes rim area, average nerve width,
|Stratus OCT by Carl Zeiss Meditec features real-time cross-sectional images and quantitative analysis software to assess the early signs and changes of glaucoma.|
disc diameter, cup diameter, horizontal rim length, cup offset, cup-to-disc horizontal and vertical ratio, cup/disc /rim area, and cup volume. The RNFL Analysis Report can compare different averages and display thickness in a chart with colored bands demonstrating a range of normative data. It can also compare sectoral and quandrant averages with normative data. To compare OD to OS, a line graph displays the RNFL thickness in both eyes. Asymmetry may be indicative of glaucomatous loss.
Carl Zeiss Meditec’s Cirrus™ HD-OCT uses spectral domain OCT to provide highly detailed HD maps and advanced analysis. This instrument incorporates the aspects of the Stratus OCT, but has better axial resolution and a scanning speed 50 times faster than the Stratus, thus allowing it to scan a larger retinal area. It also enables extremely repeatable results and visualization with exact correlation between the OCT scan and the fundus. The Auto Patient Recall feature assures patient position and settings are repeated from previous visits.
|SPECTRALIS (shown on top) features Heidelberg Noise Reduction, which filters out random speckle noise and retains only data common to the entire set of images. Labeled OCT imageof the Optical Nerve Head is shown below.|
The Guided Progression Analysis (GPA) compares RNFL thickness measurements over time and determines if any statistically significant changes have occurred. It automatically registers follow-up examinations to the baseline to ensure correct comparison and tracking. A new custom print mode generates a report of selected scans and overlays from any advanced interactive analysis screen.
The SPECTRALIS® system from Heidelberg Engineering, Inc. has an integrated OCT with a confocal scanning laser ophthalmoscope, yielding a more detailed, accurate view of the ocular structures. The TruTrack™ active eye tracking and simultaneous dual-beam imaging allow for enhanced details, high levels of measureable change and automatic rescan at follow-up.
Also unique to this system are Heidelberg Noise Reduction™, for improved image resolution, and AutoRescan™, which automatically places follow-up scans at the same location, leading to accurate repeat-ability. Heidelberg Engineer-ing offers multiple models of the SPECTRALIS SD-OCT at different price points with features that can be added later. According to the company, the SPECTRALIS platform also offers the only RNFL normative database with FoDi™ alignment and the new Posterior Pole Asymmetry Analysis. Used together, these technologies can be helpful in early detection and management of glaucoma.
Optovue Inc.’s RTVue® is a high-speed, high-resolution spectral-domain OCT. Its comprehensive glaucoma analysis includes RNFL thickness mapping, optic disc metrics, and a patented Ganglion Cell Complex
Significance Map. A robust vessel trace program allows for the analysis of scans over time which is key for the detection of glaucoma. The 3D scans provide an interactive evaluation of the macula and optic disc.
|THE PORTABLE OCT TREND Optovue Inc.’s iVue® is the compact spectral-domain version of the RTVue OCT, offering the same scanning speed and resolution as the larger system, that includes scanning and reports for retina, retinal nerve fiber, and cornea assessment. The easy-to-use, streamlined GUI and short “chart time” help with patient flow in the practice—all of which are driving demand for iVue systems.
The “en face” option offers a new perspective with a “top down” view of the optic nerve and lamina cribrosa. En face view is available as well as animation of the 3D cube, which can be exported as a video.
While OCT can provide significant information about the integrity of a glaucoma patient’s or suspect’s optic nerve, it’s not just for glaucoma. OCT has been useful in imaging a variety of posterior segment pathologies. And with manufacturers continuing to find new capabilities to incorporate in their products, OCT instruments will continue to take eyecare management to a much higher level.
Jennifer L. Stewart is in private practice at Norwalk Eyecare in Norwalk, CT.
|WHAT’S THE ROI? How can you know if getting an OCT (optical coherence tomography) system is a worthwhile investment for your practice? The key is to determine how many existing patients could benefit from OCT. Frequency of utilization—how many times a year you can submit a claim for OCT imaging—depends on the individual patient and the type and nature of ocular disease.
“Most ODs don’t think they have the patient base in their office,” says J. James Thimons, OD, of Darien, CT. “If you can go in and find 100 retina cases that are active, and 50 glaucoma patients and 75 to 100 suspects, you’ve got 250 people. You’re going to be imaging them on average about 400 images a year just on that alone—and that’s not new patients, just what you have.” At the national average of $45 a scan, 400 scans would yield $18,000 a year in revenue, or $1,500 a month.
Glaucoma patients and most glaucoma suspects with non-progressive disease would probably qualify for one OCT examination a year, says Dr. Thimons. However, if the disease is progressive or you’re able to document a medical reason for more frequent imaging in a patient with non-progressive disease, then more frequent imaging may be justified. Dr. Thimons estimates that “maybe 10%” of his glaucoma patients get scans more than once a year.
Patients with corneal dystrophies or some other form of anterior segment disease would again probably qualify for one annual OCT scan, unless the disease is progressive, according to Dr. Thimons.
A patient with active age-related macular degeneration may be eligible for up to four OCT retinal scans a year if the disease is progressive. A post-operative patient with, for example, cystoid macular edema, may be eligible for a separate OCT scan claim even in the 90-day global period, Dr. Thimons says, but check with your carrier to be sure.