2016 brings retinal imaging into starring role

Reviewed by Pravin Dugel, MD, Charles Wykoff, MD, PhD, and Marco Zarbin, MD, PhD, FACS

This has been the year of optical coherence tomography (OCT) angiography, numerous retina specialists said. Commercially available systems are available from Carl Zeiss Meditec, Heidelberg Engineering, and Optovue provide a noninvasive way to image retinal vasculature and confirm clinicians’ diagnoses of abnormalities.

“Imaging continually changes; every year it’s being used a little bit differently,” said Julia A. Haller, MD, ophthalmologist-in-chief, Wills Eye Hospital, Philadelphia.

2016 was just the cusp of OCT angiography, said Charles Wykoff, MD, PhD, Retina Consultants of Houston, and deputy-chair of ophthalmology, Houston Methodist Hospital.

“We’re starting to see a lot of podium time being spent on OCT algorithms and we’re seeing OCT angiography being incorporated into many prospective studies,” Dr. Wykoff said. For clinicians who have not yet used the technology, “using current software, projection artifact is still a challenge, potentially contributing to difficulty identifying and isolating layers from one another.” Dr. Wykoff predicts OCT angiography will become mainstream within the next 1-2 years.

“Almost every major advance in ophthalmology is, in some way, connected to imaging,” said Marco A. Zarbin, MD, PhD, FACS, chair, Institute of Ophthalmology & Visual Science, Rutgers New Jersey Medical School. “We now have in vivo imaging with spectral domain and swept source OCT that works at the level of resolution of the light microscope. With adaptive optics scanning laser ophthalmoscopy we have something that works at a very high resolution of an oil immersion lens light microscope,” but it is still structure-based.

“What we need to be truly transformative in ophthalmology is to connect structural data with function in real time,” Dr. Zarbin said. “Imagine being able to see not only the photoreceptors in a diabetic patient, but the metabolic health of those cells-how much oxidative damage is occurring, for example.” Developing clinically usable markers that “tell us something about the biological state of the cells we’re imaging” will move imaging and diagnostics forward dramatically, he said.

These types of technologies exist outside ophthalmology (e.g., nuclear imaging of atheromatous plaques with radiolabeled annexin antibodies) but usually are rather low resolution (e.g., PET scanning), he said.

“We need more precise tools,” he said. Biomarkers that can be visualized at high resolution in vivo might allow imaging technologies to be used as endpoints in future clinical trials, Dr. Zarbin said, noting the FDA accepts anatomic endpoint of the extent of atrophy as a valid endpoint in studies evaluating treatments for geographic atrophy.

Wide-field imaging “has been commercially available for more than 5 years, but new data has emphasized its clinical value for diagnosis and prognostication,” Dr. Wykoff said, especially with ultra-wide-field fluorescein angiography. The Diabetic Retinopathy Clinical Research Network’s Protocol AA is a large, fully enrolled, 5-year study “that has the potential of further informing the utility of wide field imaging in predicting diabetic retinopathy progression over a long period of time.”

Dr. Haller also believes adaptive optics are still on the horizon but “it seems to get a little closer every year in terms of how we might be able to use it clinically for diagnostic purposes.” She likens the swept-source technology to the early days of OCT-the technology was not readily available outside of research institutions, “and then it gradually moved into everyone using it all the time. We see OCT angiography moving that way, and I expect adaptive optics will follow suit.”

Dr. Haller said intraoperative OCT is on the verge of popularity, but “we’re still figuring out where it can be most useful,” she said. “As we get more of a feel for it, it will become more obvious where it can be best used. Sometimes we don’t know exactly what we’re looking at and these imaging technologies are clarifying that for us.”

Also on the horizon in diagnostics is an increasing use of telemedicine, Dr. Haller said. “We’ve been slowly increasing our ability to better identify those patients with diabetic retinopathy. We’ve also started tying in glaucoma screening because those two diseases are nicely paired for imaging.”

The combination of OCT imaging, OCT angiography with cross sectional view, and devices to view the macula plus wide-field angiography “is going to be the standard for the common retinal diseases” moving forward, Dr. Wykoff said.

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