Focus on Diagnostics

Coming soon to your diagnostic toolbox

Emerging technologies see deeper and wider to detect pathology sooner, and one day could benefit all eye care.

By René Luthe, Senior Associate Editor

Ophthalmology has had the good fortune to see technical and surgical innovations come along with heartening regularity, but keeping up with those that fall outside your specialty can be difficult. New technologies that have emerged in the field of retina diagnostics, though, not only promise better understanding, earlier detection and possibly more responsive treatments in retina; they may also bring the same benefits to other areas of eye care.

Here’s a rundown of the technologies that are moving retinal diagnostics forward.

ULTRA-WIDEFIELD IMAGING

A more global ‘gestalt’

Receiving much attention at recent ophthalmic meetings, ultra-widefield (UWF) imaging overcomes some of the limits of traditional fundus photography, which captures 30% to 65% of the retina, to give dramatically more comprehensive views in a single image.

The technology is available in the United States from two manufacturers: Optomap by Optos (Marlborough, Mass.) and the Non-Contact Ultra-Widefield Angiography Module lens that attaches to the Spectralis or HRA2 camera by Heidelberg (Carlsbad, Calif.). Optomap technology is found in Optos’ P200, 200Tx, 200Dx and Daytona products and delivers 200° views (Figure 1), while Heidelberg’s lens captures 150°.

Figure 1. Retinal vein occlusion can be identified and treated with the use of the UWF in Optomap, which provides up to a 200°, autofluorescense, red-free or fluorescein angiography image of the retina in a single capture.
COURTESY: OPTOS INC.

Justis P. Ehlers, MD, assistant professor at Cole Eye Institute at the Cleveland Clinic Lerner College of Medicine, calls ultra-widefield imaging a dramatic improvement in terms of peripheral visualization, as used in photography, angiography and autofluorescence. Traditional fundus photography gives clinicians a 30° to 50° view of the posterior pole and macula, as Michael Singer, MD, of Medical Center Ophthalmology Associates, San Antonio, Texas, points out.

Previously, getting a wider view required obtaining and montaging multiple images, which takes significant time and effort, Dr. Ehlers says. “For previous sweeps, the patient had to look in all various directions during the study, but it then required all of the work to montage the images to get a more global gestalt of the clinical situation,” Dr. Ehlers explains. UWF provides all that information in a single image.

It’s definitely a case of a single picture being worth a thousand words. “With UWF, we are able to get so many more degrees of visualization, so you realize there are lots of things out there that you may be missing,” Dr. Singer explains.

New information

“In cases such as diabetes and retinal vein occlusion, widefield angiography may actually affect what you are seeing on OCT in terms of peripheral ischemia driving increased swelling,” says Dr. Singer.

In patients with retinal vein occlusions, widefield angiography actually shows decreased peripheral ischemia when intravitreal therapies are working, and this correlates with decreased swelling on OCT, says Dr. Singer. He notes that in patients with proliferative diabetic retinopathy and neovascularization, peripheral ischemia may be much greater than initially appreciated on conventional fluorescein angiography.

UWF imaging also delivers in the management of uveitis, says Dr. Ehlers. Standard angiography can frequently under-recognize some ongoing peripheral inflammatory changes. “With widefield, you get a much better sense of the overall retinal vascular leakage and the ongoing inflammation,” he says. An additional advantage is that some patients can have UWF without mydriasis, Dr. Ehlers notes.

Better, more efficient care

Dr. Singer predicts the advantages of UWF will quickly manifest in day-to-day practice as well. The technology facilitates referrals, because co-managing physicians can share what in the image is worrisome. “In addition, as we get more image management in terms of taking care of patients in remote sites or just holding the data in electronic format, widefield angiography gives you a much better surrogate of what’s going on than conventional posterior pole angiography,” he says.

R.V. Paul Chan, MD, FACS, believes UWF is worthwhile for comprehensive ophthalmologists as well as retinal specialists, calling it “incredibly useful and could be used as a screening tool.” Pediatric ophthalmologists also should find it very helpful, he says.

“It’s very challenging to perform a dilated funduscopic exam on an uncooperative child,” says Dr. Chan, director of the retina service at New York-Presbyterian Hospital, Weill Cornell Medical College. “So I’ll get a picture using these ultra widefield imaging systems, and because the image capture can be very quick, you can get a lot of information and you can see the peripheral retina in great detail. So it’s made a big, big difference in my practice for children.” (Figure 2)

Figure 2. Retinal tears typically occur at the thin edge of the retina, outside the traditional field of view. With UWF of the Optomap, pathologies in the periphery can be identified and treated.
COURTESY: OPTOS INC.

Ready for prime time?

Richard S. Kaiser, MD, associate professor and codirector of the retina fellowship program at Wills Eye Hospital, Philadelphia, agrees that UWF offers advantages in retinal diagnosis. “There’s no question a photograph has higher resolution and is more reproducible than a drawing,” he says, but warns that UWF may yet need certain “refinements” to be amenable to clinical practice.

For starters, UWF would need to come down in price before it is widely adopted. “And it probably has to be integrated more into the platforms that we already use,” he says.

Space is another consideration. Practices would need more of it to accommodate another device. “This is a problem, because we don’t have extra rooms in our practices,” Dr. Kaiser says. “We already have OCT machines and fundus cameras and we do injections, so we need more rooms, not fewer rooms. And UWF is not going to let you get rid of any of those other devices.”

That last sentence bears repeating, because it indicates another limitation of UWF: It’s not going to let practices get rid of any of their other diagnostic devices. “Any new technology in the OCT space has to significantly change the way we practice retina — either drastically improve our diagnostic skills or allow us to implement a treatment,” Dr. Kaiser notes. “Otherwise, we have already invested a lot of money in our OCT machines.” Further, any investment in UWF may not generate any additional revenue, Dr. Kaiser notes. “So you have to justify the cost,” he says.

Specialists have differing opinions over the elemental necessity of UWF imaging in the comprehensive ophthalmology practice. Dr. Kaiser says that while UWF is a “great technology,” it is not an essential one, not even for retinal specialists. “It’s not necessarily going to change your management of the patient.”

Dr. Chan agrees. “These imaging systems may change the way we look at disease. Historically, we haven’t always been able to easily obtain good fluorescein angiograms in the far periphery. The peripheral pathology we are now seeing with these ultra widefield imaging systems may help determine how we manage patients. Many of us are now asking ourselves ‘OK, now that we can see it, what do we do about it?’”

SWEPT-SOURCE OCT

Longer, faster, wider

Currently, the DRI (for Deep Range Imaging) OCT-1 Atlantis (Topcon, Oakland, N.J.) is the only OCT to feature swept-source technology. Not yet approved by the FDA, it is undergoing study here in the United States. Advocates of the technology point to its longer wavelength (1,050 nm vs. 850 nm for SD-OCT), its imaging speed of 100,000 A scans/sec and 12-mm scan width as improvements over existing technology.

“As we get the image deeper and deeper into the eye, especially the choroid, swept-source is going to be a big deal, because we will be able to image the choroid in much greater detail, allowing clinicians to better classify the different manifestations of disease states,” says Dr. Singer. This will also allow more quantitative assessments leading to databases which will help distinguish normal presentations from disease states.

Swept-source does take OCT into new territory, says Charles W. Mango, MD, an assistant professor at Weill Cornell Medical College. “We all use OCT as our standard imaging device, whether you are a retinal specialist or a comprehensive ophthalmologist,” he says. Spectral-domain OCT — SD-OCT — is the most popular OCT platform today. It provides a 6- to 9-mm scan of the retina, and its routine resolution focus is at the level of the retina, he explains (Figure 3). “While you can achieve a very nice scan of the retina, it is difficult to acquire a single scan with simultaneous excellent visualization of the vitreous, choroid, and retina,” Dr. Mango says. “Also with a typical scan, there is relatively poor imaging of the choroid (compared to the retina) with an SD-OCT.”

Figure 3. Vitreomacular traction as viewed with SD-OCT (A) and Atlantis SS-OCT (B). Swept source shows a wider view from the optic nerve to the peripheral macula, along with vitreous adhesion to the optic nerve and a single strand of vitreous traction to the mid-peripheral macula.
COURTESY: CHARLES MANGO, MD

Deeper light penetration

In contrast, swept source OCT (SS-OCT) offers a wider scan (up to 12 mm) to deliver a widefield image from the optic nerve to the peripheral macula in a single scan. SS-OCT also allows for improved resolution, and simultaneously captures excellent views of the vitreous, choroid and retina in a single scan. Also, the swept source light source penetrates further into the choroid allowing for an “amazingly detailed view”, Dr. Mango explains. “It really gives you a good understanding of certain diseased eyes and normal eyes that you otherwise wouldn’t have.”

SS-OCT also provides clearer imaging through lens opacities than prior OCT technology may, Dr. Mango notes, which could be valuable to cataract surgeons. “A surgeon would want to ascertain for any retinal pathology before performing cataract surgery,” he adds. “SS-OCT allows for visualization through mature cataracts better than other imaging tools currently available.”

SS-OCT technology may empower more comprehensive ophthalmologists to routinely follow their patients’ retina pathologies, Dr. Mango notes. They will also have more certainty about when to refer patients. “We are looking for fluid when analyzing OCT scans. Whether it’s a diabetes patient with mild edema or a wet AMD patient with a small amount of subretinal fluid, they may be noted earlier by a comprehensive ophthalmologist using this new technology” he says.

Beyond the retina

While the relatively high cost of SS-OCT may keep it from becoming a staple of a comprehensive ophthalmologist’s practice, Dr. Singer notes that its detailed imaging could make it worthwhile for a multispecialty practice. Although comprehensive ophthalmologists are not typically looking at the deeper layers of the retina in such close detail, glaucoma specialists would benefit from what swept-source has to offer when applied to the optic nerve and nerve fiber layer.

Add to that how SS-OCT improves the retina specialist’s understanding of the choroid, and “that is where you start getting the justification” to buy the technology, according to Dr. Singer.

SS-OCT can provide clear imaging through lens opacities, Dr. Mango notes, which could be invaluable to a cataract surgeon. “That’s critical, because if you have a patient with a cataract, you want to be able to make sure you know the retinal pathology well,” he adds.

Patient retention tool

But Dr. Mango believes as well that SS-OCT will interest comprehensive ophthalmologists because it will enable them to retain more of their patients and follow the course of their ocular problems.

As with UWF, SS-OCT can pick up pathology that a smaller scan from earlier-generation OCT cannot, Dr. Mango notes, giving the comprehensive ophthalmologist greater certainty about when to refer the patient to a specialist. “Usually we are looking for fluid, so whether it’s a diabetes patient with early edema in a peripheral macula, or whether it’s a patient with subretinal pocket of fluid from a central serous retinopathy or a wet AMD patient, these patients likely will be noted earlier by a comprehensive ophthalmologist to be sent out vs. when it’s too late,” he says.

Dr. Ehlers takes a more guarded view for now. “Is swept-source going to change the way we manage patients day-to-day? I think the jury is still out as far as overall clinical utility compared to spectral domain OCT. It will certainly enhance penetration, for example for choroidal imaging, as well as increase the range over which visualization can occur, such as with simultaneously visualizing the vitreous and choroid,” he says. OM