Emerging Innovations In OCT Technology
Five OCT manufacturers discuss the newest features.
OCT applications in use or in development promise positive results for patients ranging from the very young to the elderly, as physicians get new tools to aid in the management of retinal vein occlusion (RVO), tumors, cancers, AMD and retinoblastoma and diabetic retinopathy.
That last condition, in fact, is at the forefront of recent developments from three California companies — Nidek, Inc., of Fremont; Carl Zeiss Meditec, Inc., Dublin; and Heidelberg Engineering, Inc., Carlsbad. Heidelberg has developed a device that one Texas doctor says augurs an appreciable benefit for a sizable portion of his state’s population.
This article reviews the most recent innovations from five companies that manufacture and market OCT devices.
Non-Contact Ultra-Widefield Imaging
Heidelberg Product Manager Adam Doherty discussed two of his company’s applications in retinal diagnostics, one of which addresses enhanced care for diabetics. That is the Heidelberg Non-Contact Ultra-Wide field Angiography Module, which offers a wide field-of-view with a one-shot image.
“It delivers evenly illuminated and undistorted, high-contrast cSLO images, even in the periphery,” Mr. Doherty says. “The lens attaches easily to any Spectralis or HRA2 camera head and is interchangeable with the existing lens. It makes it easy to detect and monitor clinically relevant peripheral changes like microaneurysms, neovascularization, perivascular leakage or areas of non-perfusion.”
Non-contact ultra-widefield imaging is designed with a wide field of view to enhance recognition of the extent of such conditions as retinal vein occlusion, diabetic retinopathy, and retinal tumors and cancers (Figure 1).
Figure 1. Fluorescein angiography of diabetic retinopathy obtained with the Spectralis Non-Contact Ultra-Widefield imaging. The moveable camera head of the Spectralis further extends the reach out into the far periphery.
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“It also helps the clinic workflow because you can capture a single image with a wide field-of-view that would have normally taken seven or more images to create a composite of the same area,” Mr. Doherty adds.
One Physician’s Review
David Brown, MD, a retina specialist with Retinal Consultants of Houston, praises the angiography module, saying he “can’t live without it” when it comes to treating diabetics. He says diabetics comprise a sizable portion of his patient base because large numbers of the Hispanic population in Texas past age 40 are diabetic.
“In the future, it will be mandatory,” Dr. Brown says of wide-field imaging for diabetic patients. Well over half the patients in his practice already require wide-field imaging, he adds.
Dr. Brown’s practice acquired the Heidelberg application as an add-on to the Spectralis already in the practice. He previously used a different wide-field system.
Without wide-field imaging, angiograms visualize only 30% to 40% of the retina, according to Dr. Brown. With a conventional angiogram, it is easy to miss neovascularization and ischemia. However, wide-field imaging allows the physician to see what is happening throughout the fundus, Dr. Brown says.
“Before we had wide-field imaging, I didn’t know what I was missing; you handicap yourself without it,” Dr. Brown says.
Scanner Laser Imaging
Heidelberg also offers MultiColor imaging, which involves scanner laser imaging that Mr. Doherty says brings “a new dimension” to non-invasive multi-modality fundus imaging with the Spectralis line. Simultaneous imaging with multiple laser colors selectively captures and portraits diagnostic information originating from different retinal structures within a single examination (Figure 2). Spectralis MultiColor imaging delivers high contrast, detailed images even in difficult patients, including those with cataracts or nystagmus, Mr. Doherty says.
Figure 2. Images of geographic atrophy illustrate the different views available with the Spectralis MultiColor imaging: A) color fundus photo; B) MultiColor Blue image; C) MultiColor image; D) MultiColor Green; and E) MultiColor Infrared.
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“Because the MultiColor images are using multiple wavelengths, they give information on pathology at different depths within the retina, providing more information than traditional fundus images,” Mr. Doherty says. “This can be very useful in many disease states including AMD, tumors, cancers, DME, and RVO.”
Dr. Brown also praises for multi-color imaging, especially when imaging AMD, in that it can visualize reticular drusen. Blue light facilitates this function. He adds the multi-color imaging is also helpful for documenting tumors.
CARL ZEISS MEDITEC
Cirrus 5000, 500 and Photo
CZM introduced a new family of OCT products at the 2012 AAO meeting in Chicago. The new Cirrus family includes two new Cirrus HD-OCT devices, models 5000 and 500; and two new integrated multi-modality OCT and fundus imaging systems, the Cirrus photo models 800 and 600. The Cirrus HD-OCT provides tools to characterize and diagnose such conditions as DR, DME and RVO.
The Cirrus HD-OCT 5000 features, for advanced care, FastTrac retinal tracking that allows the user to capture high-resolution B-Scans in identical locations from visit to visit, providing accurate assessments of changes in pathologies. Cirrus HD-OCT 5000 is configured with high-resolution visualization capabilities and applications, such as Advanced RPE Analysis to track retinal pigment epithelial integrity.
Figure 3. Views from the Advanced RPE Analysis application available with Cirrus: A) Cirrus photo of the RPE; B) HD-OCT image of the RPE in a detached retina.
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Figure 4. To align HD raster in the same position from visit to visit, FastTrac uses a tracking green line (A) to align scans, and allows toggling back and forth between current (B) and prior (C) B-scans.
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The Cirrus photo 800 and 600 multi-modality systems combine Cirrus OCT technology with full-featured mydriatic/non-mydriatic fundus imaging in one integrated, compact system. Physicians can correlate data from high-density OCT cubes, thickness and layer maps with results from color fundus, and angiography images in one session without having to move the patient.
The Cirrus photo 800 is designed to support advanced disease management with fluorescein and ICG angiography, color and fundus auto-fluorescence imaging, and OCT technology in an integrated imaging solution.
Advanced RPE Analysis
The new Advanced RPE Analysis application allows physicians to assess the integrity of the RPE layer and monitor changes. It provides visualization and quantitative tools to assess RPE and AMD patients, including high-density cross-sectional images that delineate elevations of the RPE and en-face images to reveal disruptions in the RPE (Figure 3).
Cirrus uses proprietary algorithms to measure elevation of the RPE layer from the baseline (normal RPE) plane, resulting in area and volume measurements of the elevations. Cirrus can determine when RPE is absent in a patient or has lost integrity, as the OCT beam penetrates into the choroid. Cirrus maps and measures the affected area and provides distance measurement from the fovea to the affected area, which is essential in assessing the potential for loss of vision.
Cirrus Advanced RPE Analysis has applications for non-exudative and exudative AMD patients, important because an appreciation of changes in drusen volume using SD-OCT imaging is a strategy for following disease progression. The application also measures increase in volume and area of vascularized PEDs, which may help predict disease progression and the need for more aggressive anti-VEGF therapy.
FastTrac Retinal Tracking System
The FastTrac Retinal Tracking System compares live LSO images with reference LSO images. During scanning, eye movements create an offset between the live LSO image and reference LSO image; FastTrac uses these offsets to redirect the OCT scan, resulting in a free scan taken at the precise location on the reference image (Figure 4).
FastTrac also provides accuracy and reproducibility of single-visit measurements and an expanded number of high-quality B-scans to visualize structures of interest. SriniVas Sadda, MD, director of the retina service at University of Southern California Keck School of Medicine, Los Angeles, says the Cirrus FastTrac is “very helpful for removing any eye motion from the larger cube scans without disturbing my patient flow because it moves very quickly.”
Nidek touts its MC-500 Vixi laser scanner, which incorporates scan delivery systems and integrates a multi-color laser photocoagulator into one comprehensive pattern, allowing rapid and optimal power laser emission for laser photocoagulation with selection of various colors and 21 customizable scan patterns.
The device, FDA-approved and currently in use, is especially important to the treatment of DR and DME, says Gary Pehrson, Nidek business development consultant.
The MC-500 Vixi laser scanner causes less pain than similar applications and “is four times faster than conventional photocoagulation,” according to Mr. Pehrson. It “targets disease tissue on three wavelengths” and is also vital to the treatment of micro-aneurysms, he adds
The speed factor also is especially helpful for patients living in rural areas, as only one session is needed rather than four or five. “They won’t have to come back for a second visit,” Mr. Pehrson says.
The scanner allows selection of one, two or three wavelengths — green, yellow, and red — enabling the freedom to select the necessary color or combination to increase efficiency of treatment. In eyes with retinal hemorrhage, the red (647-nm) wavelength achieves better penetration, he says.
The MC-500 Vixi, with triple emission mode, provides auto-manipulation and scan modes, allowing for mode selection appropriate for a specific pathology:
• single mode for conventional laser emission;
• auto-manipulation mode for repeated laser emission with variable interview times and conventional coagulation setting in a selectable scan pattern, which allows the surgeon to continue laser emission while confirming the coagulated spot; and
• scan mode for repeated laser emission with a fixed time interval, high power and instantaneous speed.
Bioptigen,of Morrisville, NC, has the first FDA-cleared market imaging technology for premature infants, the Envisu hand-held imaging system. Envisu C-class SDOIS is the first ophthalmic OCT imaging systems specifically cleared for hand-held imaging of patients, from premature infants to adults, whether upright, supine, confined or ambulatory. Interchangeable lenses allow clinicians to image various structures of the eye, from cornea to retina.
The systems, FDA approved in 2012, acquire and display images in real time, at 32,000 lines per second. This allows for rapid alignment and acquisition of full volume images in one to three seconds, according to Bioptigen. The device has an intrinsically wide 70° field of view, which gives it the flexibility to explore physiology away from the central fovea.
Two configurations are available: Users can choose from two light sources (HR, VHR) and up to four interchangeable imaging lenses for both Envisu C2200 (which offers finer pixel resolution) and C2300.
In addition, Envisu C2300-VHR offers finer pixel resolution, while C2300-VHR offers optimum balance of high resolution and wide depth of field for exploring anterior and posterior pathology. The systems should be especially valuable for research and diagnostic support in dealing with retinoblastoma, a leading cause of blindness among children, according to Eric Buckland, PhD, Bioptigen president and CEO.
Figure 5. 3-D scans from the Topcon DRI OCTi-1 illustrate the depth of the 1050-nm wavelength: A) pigment epithelium detachment; B) vitreo-macular traction; C) DME.
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It is also valuable in treatment and research of tumors and in dealing with AMD, Dr. Buckland says. The retinal-scanning devices are especially effective for patients not well-suited to imaging with traditional table-top devices.
TOPCON MEDICAL SYSTEMS
Topcon, of Oakland, NJ, has in the works a device for posterior imaging targeting AMD and DR. Robert Gibson, vice president of marketing at Topcon, says the DRI OCTi-1 a swept source OCT utilizes a wavelength of 1,050 nm. Useful for monitoring AMD and DR, and already in use in Europe and Japan, the retinal scanner enables doctors to “see things they haven’t seen before,” Mr. Gibson explains.
Topcon hopes to submit an FDA application later this year for DRI OCT-1, which has a fast scanning speed of 100,000 A-scans/sec. The 1,050-nm wavelength penetrates the macula and retinal layers more deeply than current OCTs, which utilize wavelengths in the 850-nm range.
The device has the capacity to image deeper anatomic structures with less influence in scanning. It also can visualize the entire tomogram with high sensitivity.
The invisible scan line of the DRI OCT-1, because of its 1,050-nm wavelength, contributes to reduced patient eye motion, furthering fast examination workflow and enhanced successful scanning.
DRI OCT-1 will also increase scan coverage of the macula area to disc, thanks to the 12-mm wide scan, and may be useful to evaluate observed abnormalities. An instant single shot of that scan area should cut down on patient fatigue. RP