OCT-A

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THE LATEST ADVANCE IN OCT TECHNOLOGY HELPS MANAGE PATIENTS WITH GLAUCOMA.

OCT in the optometric practice has been steadily gaining ground in recent years. The gold standard for glaucoma management has been, and still is, optic nerve head assessment and visual field perimetry, but here comes OCT-A technology to up the ante.

“For the first time we’re able to quantify blood vessel density which we haven’t been able to do. We’ve been able to look on a structural level, but we haven’t been able to look at what’s actually happening at a microvascular level,” said Julie Rodman, OD, MS, FAAO, associate professor, Nova Southeastern University, Fort Lauderdale, FL. “This has been really helpful to identify disease a lot earlier than we have been able to before. It’s a non-invasive way to view retinal vasculature and see where the damage has occurred, not just confirm that it occurred.”

“OCT-A was created not to take the place of OCT but to provide a different dimension.” Julie Rodman, OD, MS, FAAO, Associate Professor, Nova Southeastern University

THE DIFFERENCE BETWEEN OCT AND OCT-A

OCT evaluates the structure of the retina—it provides an in-vivo analysis of both the retinal and choroidal anatomy, she explained. “OCT-A was created not to take the place of OCT but to provide a different dimension,” said Rodman. “OCT-A provides visualization of the peripapillary capillaries and correlates more strongly with a patient’s visual function by providing a functional analysis. Reduced peripapillary perfusion correlates with focal defects on visual field, RNFL and GCC thickness. Using them together, we get a structural and functional analysis side by side.”

WHAT IT MEANS FOR PATIENTS WITH GLAUCOMA

“With regards to management of glaucoma, OCT-A opens the door for personalized glaucoma care,” said Carolyn Majcher, OD, FAAO, chief of the Retina Clinic and assistant clinical professor, University of the Incarnate Word Rosenberg School of Optometry in San Antonio, TX.

While it’s been known for some time that vascular dysregulation contributes to the pathology of this multifactorial disease, for some eyes this may be more of a leading player than others. “When I see a glaucoma patient with substantial perfusion compromise as visualized with OCT-A, I am more inclined to select a vasoactive agent such as dorzolamide,” said Majcher. “Similar to pattern ERG testing in glaucoma, perfusion compromise is at least initially a reversible thing. So it may prove to be useful in providing feedback to the clinician as to whether adequate treatment has been achieved.”

In the future, she believes that doctors may be titrating treatment to achieve “perfusion targets” rather than target IOP levels alone.

“With regards to management of glaucoma, OCT-A opens the door for personalized glaucoma care.” Carolyn Majcher, OD, FAAO, Chief of the Retina Clinic and Assistant Clinical Professor, University of the Incarnate Word Rosenberg School of Optometry

BENEFITS OF OCT-A

“The literature that I’ve read and the experience that I’ve had is that OCT-A is very good at identifying early damage in primary open angle glaucoma (POAG); earlier than we would see with visual field or other modalities,” said Rodman. “The reason is that primary open glaucoma results from both mechanical factors and vascular dysregulation, and a vascular problem is going to be picked up on a vessel density analysis provided by OCT-A analytics.”

In angle closure glaucoma, the elevated intraocular pressure affects the RNFL measurements before affecting the vascular density; thus OCT-A may be a more desirable objective screening tool for POAG.

OCT-A TECHNOLOGY

Optovue’s Avanti AngioVue system is available in three configurations: AngioVue Comprehensive, AngioVue Essential and AngioVue Retina. The latter two can be upgraded to the Comprehensive system. “AngioVue Essential provides streamlined OCT-A image interpretation in a single page report allowing for an efficient way to evaluate and manage retinal disease that may necessitate a referral.” Its high-resolution, non-invasive imaging of retinal vasculature helps visualize ocular disease. The single-page report displays individual layers of retinal vasculature alongside structural OCT B-scans.

With AngioAnalytics, doctors can measure foveal avascular zone parameters, areas of abnormal flow in the outer retina and choroid, and vessel density. Its multi-scan analysis allows for assessment of progression at each patient visit and trend reports help predict change over time. In addition, Optovue’s 3D projection artifact removal (3D PAR) software removes shadows from the vessels to improve image quality.

Carl Zeiss Meditec, Inc. offers ZEISS AngioPlex on its CIRRUS HD-OCT. “AngioPlex OCTA imaging is able to noninvasively detect and highlight reduced perfusion and capillary vessel density loss in glaucomatous eyes within both the peripapillary and macular regions,” said Majcher. “It is therefore another tool in my ‘glaucoma tool belt’ along with other objective measures such as retinal nerve fiber layer (RNFL)/ganglion cell complex thickness that aids in glaucoma diagnosis and detection of glaucomatous progression.”

New software versions are expected to include a 4.5 x 4.5mm optic nerve head OCT-A scan that automatically visualizes the radial peripapillary capillary network that is affected in glaucomatous eyes.

Heidelberg Engineering recently received clearance from the U.S. Food and Drug Administration for its OCT Angiography Module. The OCT Angiography Module can be added to new and existing upgradeable SPECTRALIS devices with the OCT2 Module. The upgrade delivers a lateral resolution of 5.7 μm/pixel. In addition, the module and the device’s TruTrack Active Eye Tracking allows the fine capillary networks to be visualized in great detail and its PAR tool utilizes information from the superficial vascular plexus to remove artifacts from OCT-A images and enables a more precise visualization of vascular structure and pathology.

While Topcon Medical’s OCT-A technology is not available on its instruments in the United States, the swept source technology in its DRI OCT Triton is still a valuable tool in a glaucoma diagnosis and management. “With the Triton SS-OCT, I can see the vitreous, I can image the retina, I can image the choroid,” said Victor Gonzalez, MD, founder of the Gulf Coast Eye Institute in the Rio Grande Valley in Texas. “This is so important in helping me decide how my treatment moves forward, or how I need to alter that treatment.” In addition, its en face technology allows visualization of various layers of the retina.

WHAT ARE YOU WAITING FOR?

“Every optometric practice right now should hopefully have an OCT,” said Rodman. “I think in the next decade, every machine will have OCT-A on it, but for now, unfortunately, it’s still a novelty for a lot of folks.” But she assures that once novice users experience the technology and learn it, it will become not only easier to use but an essential part of the glaucoma practice. O|O

WHERE TO FIND IT

Carl Zeiss Meditec, Inc.
800.342.9821 | Meditec.Zeiss.com/USA

Heidelberg Engineering
508.530.7900 | HeidelbergEngineering.com

Optovue Inc.
866.223.1130 | Optovue.com

Topcon Medical Systems, Inc.
800. 223.1130 | TopconMedical.com

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