Software Upgrades Take SD-OCT to Greater Levels
Software Upgrades Take SD-OCT to Greater Levels
From correcting and registering imperfect scans to offering in-depth change analysis over time, the latest SD-OCT software delivers.
BY ERIN MURPHY, CONTRIBUTING EDITOR
The choices in spectral domain optical coherence tomography (SD-OCT) devices have multiplied in the three years since they've hit the market, but the technological advances in software capabilities have been even more dramatic. Manufacturers continually enhance their software, often rolling out new features or major upgrades more than once a year.
This year and next, eyecare practitioners can expect to see software that enhances operator independence by removing image artifacts caused by axial eye movement and registering sequential scans after acquisition, even if the technician isn't precise.
Software advances in the RTVue-100 (Optovue) enhance automation and operator independence. "The recent update to software version 4.0 automates much of the image acquisition processes that used to be manual," says Ian Benjamin Gaddie, OD, FAAO, a private practitioner at Gaddie Eye Centers in Louisville, Ky., where he's also adjunct associate professor of optometry at Northeastern State University College of Optometry. "You had to mark the edges of RPE and outline the optic nerve, and an inexperienced operator might not locate them correctly. Now the software does it automatically."
But operator independence isn't the only burgeoning trend. Manufacturers are making dramatic advances in software to help track changes over time in patients with glaucoma and retinal disease. Eyecare practitioners continue to explore the unique imaging capabilities of SD-OCT, and the technology is helping optometrists retain patients instead of making referrals.
SD-OCT collects an enormous amount of data, and software is continually improving the ability to harness that data in practical ways. One of the most important capabilities of SD-OCT involves recording and registering images, so eyecare practitioners can track changes over time. Whether you're managing a patient's glaucoma or monitoring potential retinal changes, SD-OCT manufacturers have developed software to help. You can view images side by side, and various software products display measurements for ocular structures, compare the numbers against normative databases and highlight areas of change.
Robert W. Dunphy, OD, FAAO, practices at VA Boston Healthcare System, where he uses the Spectralis HRA+OCT (Heidelberg) to manage glaucoma suspects, patients diagnosed with glaucoma and patients with retinal disease. "The SD-OCT technology helps me identify high-risk glaucoma patients, differentiate various types of maculopathy and monitor patients for change over time," Dr. Dunphy explains. "The capacity to reliably determine change or stability over time enhances my ability to make appropriate decisions about intervention."
According to Dr. Dunphy, change analysis begins with properly registered scans and ends with solid decision-making assistance. "Spectralis has many strong features, but I think the most important is its TruTrak image registration, which registers images during the scan acquisition and during serial scans. TruTrak image registration generates excellent OCT and CSLO image quality, as well as accurate follow-up comparisons that enable clinicians to make very reliable determinations about patients' status over time," he says. "Clinicians can then use this data to identify stable glaucoma and retinopathy and distinguish those conditions from deteriorating or acute disease. At this point, we can make the best possible decision, whether it involves a prompt referral, no intervention or continued chronic therapy and surveillance."
Unique Glaucoma Imaging
SD-OCT continues to give optometrists a view of ocular structures they couldn't obtain with any other technology — a view that has a significant impact on diagnosis and decision-making.
Dr. Gaddie considers the RTVue-100 valuable for several purposes. "Primarily, I use SD-OCT to evaluate glaucoma suspects, retinal disease and vitreomacular interface problems such as macular holes," he explains. "The technology enhances decision-making for glaucoma and AMD management, as well as diabetic retinopathy and nondiabetic macular edema. And the RTVue-100 has the largest normative database with ethnic considerations."
Certainly, SD-OCT technology gives Dr. Gaddie some advantages that other technologies don't. "One of the unique advantages is its ability to look at the ganglion cell layer in the foveal layer as it relates to glaucoma," he says. "The RNFL has greater variability than the macular layer. That is, two normal patients may have very different RNFLs, while their macular layers are more consistent. The test is a uniform way to determine defects in the RNFL as a precursor to early glaucoma."
Figure 1. 3D OCT-1000 from Topcon
These applications have made SD-OCT an integral part of Dr. Gaddie's work, and he recommends SD-OCT to his colleagues. "It's hard for me to say that ODs need to have an SD-OCT device, but most organized groups recommend the use of a device to evaluate structural integrity in glaucoma," he says.
Exceptional Retina Capabilities
Like glaucoma diagnosis, detecting retinal problems is all about identifying the earliest signs of disease to prevent vision loss. SD-OCT enhances that ability.
Jerome Sherman, OD, FAAO, is in private practice at The Eye Institute and Laser Center in New York City, where he's also a distinguished teaching professor at SUNY College of Optometry and the Schnurmacher Institute for Vision Research. He has experience using four different SD-OCT systems in his work with retinal and optic nerve disorders.
"There are some differences between the devices, but they're all extraordinarily helpful in gathering information that we can't get clinically," Dr. Sherman explains. "For example, we can see lesions that are invisible with ophthalmoscopy."
Dr. Sherman is pleased that SD-OCT gives him an entirely new imaging capability. "Perhaps the most important aspect of SD-OCT is that it allows us to see the photoreceptors integrity line. For the first time, we can see this biomarker for both rod and cone integrity. No other technology can do this," he says.
Currently, Dr. Sherman is using the 3D OCT-1000 (Topcon) to take nearly simultaneous SD-OCT and fundus images. "The advantage is that we can see a lesion on OCT and compare it directly with the fundus, or check a fundus image abnormality on OCT," Dr. Sherman says. "The direct comparison is clinically valuable, and it's also great for educating patients and optometry students."
Figure 2. 3D SDOCT with Handheld Probe from Bioptigen
Because of the advanced capability of SD-OCT to detect retinal disease with precision, the need to refer patients isn't as urgent as before. Physicians used to refer patients because they detected or suspected a problem and wanted patients to undergo advanced testing. With SD-OCT, some of the "advanced testing" occurs in their own practice, so they can retain more patients and avoid referrals. This is true not only because SD-OCT provides great images, but also because its software analyzes the data and compares it against normative data.
Jeffry D. Gerson, OD, FAAO, who's in private practice at WestGlen Eyecare and Omni Eye Center of Kansas City, Kansas, uses the Cirrus HD-OCT (Carl Zeiss Meditec) primarily for diagnosing, recording and tracking retinal disease. He acknowledges that what one diagnostic instrument can't detect, SD-OCT will. "When a patient's vision isn't quite right but the slit lamp doesn't reveal anything, SD-OCT can help identify the problem," he explains.
That certainly keeps patients in Dr. Gerson's practice. "I can diagnose a problem, determine if it requires treatment, and then evaluate whether the treatment is something I can perform or prescribe. The ability to accomplish this without referring a patient elsewhere for further testing helps me retain patients," Dr. Gerson says. "If a practice diagnoses enough pathology — and we all have more than we think we do — then we can help SD-OCT pay for itself."
Figure 3. Cirrus HD-OCT from Carl Zeiss Meditec
Your Options for SD-OCT
If you're thinking of purchasing an SD-OCT device, you have many options. Currently, six companies manufacture SD-OCT instruments. Canon likely will become the seventh later this year. Here are your choices:
• 3D OCT-1000 (Topcon) — The Topcon 3D OCT-1000 system combines a color nonmydriatic retinal camera with the latest Fourier Domain OCT technology. The easy-to-use, intuitive TrueMap software enables dynamic viewing of the data, providing 3D, fundus and 2D images simultaneously. Pin-Point registration properly indicates the location of the OCT image within the fundus image.
In addition, the compare function allows users to see serial exams in a comparison view and apply different analytical tools. The seamless integration of the 3D OCT-1000 with Topcon IMAGEnet provides true connectivity and access to images at all times.
Topcon just released version 2.2 of its TrueMap 3D OCT software, which has an automatic alignment function that removes image artifacts caused by axial eye movement while preserving the true anatomical structure of the retina in the image. The measurement software enables physicians to visualize four layers of the retina, and it can seamlessly import data from the Stratus time domain OCT device (Carl Zeiss Meditec). Finally, the 3D OCT-1000 comes with EyeRoute On Board software — Topcon's advanced image management system.
• 3D SDOCT with Handheld Probe (Bioptigen) — With its SDOCT device, Bioptigen is targeting two markets: ophthalmic surgeons who can benefit from a handheld OCT probe for pediatric and adult patients in the operating room, and preclinical researchers studying animal models of ocular disease, diagnostics, therapeutics and treatment procedures. It traverses these needs through a versatile choice of subject-specific retina and cornea bores and stages tailored to various animal and human subjects.
Figure 4. RTVue from Optovue
A range of scan heads, such as handheld probes, clinical scanners and OCT microscopes enhance 3D SDOCT's flexibility and lifetime value for researchers. The SDOCT optical engine is physically robust, enabling worry-free system transport between remote sites. An optional broadband light source is available for ultra high-resolution images (less than 3 micron depth-independent axial resolution in tissue).
With real-time acquisition and display, and customizable, protocol-driven operations, the 3D SDOCT system ensures workflow efficiency. The Bioptigen InVivoViewClinic software includes volume intensity projections that generate en-face images similar to fundus images of the retina, establishing accurate cross-sectional image registration. Users have full access to raw OCT data and can choose to register and average an arbitrary number of individual scans. On-screen calibrated calipers and Doppler SDOCT imaging are included in the standard application.
• Cirrus HD-OCT (Carl Zeiss Meditec) — With resolution of 5 microns and repeatability of 2.5 microns, Cirrus HD-OCT captures a full cube of retinal scans in just 2.4 seconds. Precise registration and proprietary algorithms provide 2D and 3D images, layer segmentation and optical biopsies for assessment of the retinal condition and change.
Designed for efficiency, Cirrus HD-OCT offers easy and fast scan acquisition, a small footprint, and a modern integrated design that fits in the corner of a room.
The new software version 4.0 features change analysis to monitor disease progression and therapeutic outcomes for retina and glaucoma. Macular Change Analysis provides visual and quantitative comparison of two exams. Post-acquisition registration and the unique Fovea Finder function ensure the accuracy and precise repeatability of macular thickness measurements.
For glaucoma, Guided Progression Analysis compares RNFL thickness measurements from the Optic Disc Cube scan over time and determines if statistically significant change has occurred. The results show event analysis, trend analysis and a quantified rate of progression. Anterior segment imaging requires no additional add-on lens and provides visualization of the angle and central corneal thickness measurement.
Figure 5. Spectralis tracking OCT from Heidelberg Engineering
• RTVue (Optovue) — The RTVue completes 51,700+ A-scan 3D imaging in 2.2 seconds. Physicians can review a 3D presentation, rotate the images, rapidly scan through B-scans and zoom in for a better view. The system offers full retinal, inner retinal and outer retinal thickness maps and metrics, as well as a 0.35-second complete nerve head analysis for glaucoma diagnosis. It's the only commercially available OCT system that's FDA-approved for both corneal and retinal imaging.
Technicians can choose from two scan-depth ranges (2 mm for imaging the macula and 2.3 mm for imaging a tilt disk), as well as two image modes for enhanced results (vitreo mode for vitreoretinal tissue and choroids mode for chorioretinal tissue). The RTVue has an in-tissue depth resolution of 5.0 microns and a transverse scan resolution of 15 microns.
The device has internal and external fixation, as well as a video fundus camera that delivers near-infrared images of the retina. The fundus image can import and register from any digital system. Technicians can export scans or reports from the RTVue to image management or electronic medical record applications.
• Spectralis Tracking OCT (Heidelberg) — Heidelberg Engineering has added two new models to the Spectralis Tracking OCT product line. There are now five distinct models with up to six imaging modes, including the competitively priced Spectralis OCT, which sells for less than half the price of the original Spectralis HRA+OCT model.
Designed with general practitioners in mind, the new Spectralis OCT simultaneously captures infrared fundus and SD-OCT images. It also has a user interface designed for fast, easy scanning, and like all Spectralis models, it's built with TruTrack active eye tracking.
All Heidelberg SD-OCT systems capture OCT images at 40,000 A-scans per second. They use the proprietary TruTrack eye-tracking technology that recognizes, locks onto and follows the patient's retina during scanning, and automatically places follow-up scans (AutoRescan) to ensure accurate monitoring of disease progression and treatment. TruTrack also enables the proprietary Heidelberg Noise Reduction feature, which produces scans that show retinal layers and detail never seen before.
Figure 6. Spectral OCT/SLO from OPKO/OTI
• Spectral OCT/SLO (OPKO/OTI) — The dual imaging of OCT and the scanning laser ophthalmoscope (SLO) occurs through the same optics for pixel-to-pixel correspondence. The confocal SLO image of the fundus provides accurate point-to-point registration and orientation of the B-Scan OCT image, seen onscreen in real time. The system generates high-resolution B-scan images, 3D tomographic and topographic data, optic nerve and RNFL data analysis as well as automated "Compare" analysis of progression and/or regression of changes over time. Multi-OCT scanning modes allow clinicians and operators to optimize and customize the best scan for the specific disease and practice for maximum efficiency. The Spectral OCT/SLO also can be combined with optional microperimetry for retinal function testing and follow up in retina and glaucoma diseases. The SLO is used for real-time tracking of the retina during the exam. A cornea anterior Segment OCT scanning feature is also available as an option.
An Exciting Year
Advances in SD-OCT make the technology more exciting than ever. It's fast — just seconds per scan — and it provides rapid data processing. The software interprets data to help with clinical decision-making, even compensating when technicians aren't precise.
SD-OCT is visually engaging, enabling you to look at different slices of data, such as a virtual biopsy, and extract ocular structures for closer examination. You can see signs of pathology and share them with patients. And in the year to come, software enhancements will almost certainly add to the clinical advantages of SD-OCT. OM
Optometric Management, Issue: July 2009