The Evolving Role of Imaging in Diabetic Eye Disease

New advances promise to alter how physicians view and treat diabetic eyes.

BY ERIN MURPHY, CONTRIBUTING EDITOR

At every stage of diabetic eye disease, from subtle blood vessel damage to more evident lesions such as hemorrhage, edema, neovascularization, and even retinal detachment, several imaging modalities enable physicians to detect changes and intervene. And today, exciting new technologies and treatment models are emerging. They promise to help physicians detect and treat diabetic eye disease earlier to help preserve sight.

PRIMARY CARE SCREENING

For many diabetic patients, imaging is an important part of the screening and documentation process. Doctors use imaging not only to detect disease, but also to establish baseline pathology for future reference. Traditionally, images were acquired when primary eye care providers referred diabetic patients to retina specialists for evaluation. Advances in telemedicine and the availability of easy-to-use nonmydriatic fundus cameras have allowed these images to be taken in primary care settings and then sent to specialists for remote diagnosis.

FIGURE 1. Diabetic retinopathy in the deep capillary layer as seen with OCT Angiography (AngioVue Imaging System by Optovue).

“The epidemic of diabetes is outpacing the number of specialists available to evaluate patients for the disease,” explains Srinivas R. Sadda, MD, President and CSO of Doheny Eye Institute at UCLA. “To ensure everyone gets screened, we really need to take advantage of advances in imaging and broaden the use of tele-ophthalmology models already in place in a few limited areas across the country.”

Michael A. Singer, MD, Managing Partner at Medical Center Ophthalmology Associates in San Antonio, says there is an ongoing “revolution” as more primary care doctors begin working to identify diabetic pathology. From the old paradigm where the retina specialist was the sole source of screening and care for diabetic eye disease, we are seeing a shift to a new paradigm in which primary care offices obtain initial images to screen for diabetes. Dr. Singer explains that the images are sent to third-party readers who identify which patients need to see a retina specialist. Primary care doctors face significant incentives to adopt the new model.

“Insurance companies and the government provide incentives to boost a primary care practice’s Healthcare Effectiveness Data and Information Set (HEDIS) numbers. Diabetic eye exams are one of the components of the HEDIS score. The more exams a doctor performs, the better his chance of being recognized as a 4- or 5-star provider under the HEDIS criteria,” Dr. Singer says. “Primary care physicians are working with third-party companies that provide the nonmydriatic fundus camera and interpretation of the photographs. They receive insurance incentives and income for co-managing the disease. Although these exams aren’t a replacement for a dilated eye exam, they do allow patients to be screened who might otherwise have fallen through the cracks in the medical system.”

ULTRA-WIDEFIELD IMAGING

For years, retina specialists most commonly used a color fundus flash camera to screen diabetic patients. The field of view for that image was limited to 9mm or 10 mm, so doctors would pan around the retina and capture a series of photos. With the dramatic advance of new nonmydriatic ultra-widefield imaging, physicians can photograph the entire retina in one shot.

Dr. Sadda uses an Optos ultra-widefield device to document and follow diabetic retinopathy. It allows him to detect and monitor blood vessel damage and its sight-threatening effects, such as neovascularization, hemorrhage and retinal detachment.

“One of the things we’re excited about with widefield fluorescein angiography is that it enables us to see areas in the periphery that have poor blood flow, a common problem in diabetic patients that we couldn’t visualize before. We can actually see where vessels begin and end in the periphery,” Dr. Sadda explains. “And now that we can see this poor blood flow, we’re very interested in what to do with that information. How and when should we treat it? How does poor blood flow affects response to treatment? We don’t have all the data we need yet, but it’s an exciting area for study.”

FIGURE 2. Both images (taken at the same time) show the left eye of a 34-year-old male with proliferative diabetic retinopathy. Notice that the ultra-widefield Optos image (top) shows the entire extent of the traction retinal detachment while the traditional fundus photo (bottom) does not.
Images courtesy of Michael A. Singer, MD

Dr. Sadda points to a 2013 study¹ led by researchers at the William P. Beetham Eye Institute, part of the Joslin Diabetes Center in Boston, that showed diabetic patients with lesions occurring outside the central retina progressed faster than those with central lesions. This small study of 103 patients is being followed by a larger study led by the Diabetic Retinopathy Clinical Research Network. The objective of the second study² is to determine whether ultra-widefield imaging improves the physician’s ability to assess diabetic retinopathy and its potential to worsen, compared to standard images.

“This study has the potential to dramatically alter how we use imaging in the care of diabetic patients, influencing how we think of and screen for diabetic retinopathy,” Dr. Sadda says. “This may be the start of a process in which we move from a qualitative system for assessing the severity of the retinopathy based on a small region of the retina, to a more quantitative and precise assessment based on the entire retina.”

OCT ANGIOGRAPHY

OCT continues to be the primary imaging modality used to monitor diabetic macular edema before, during and after treatment.

“Using OCT, I follow the edema carefully to decide if treatment is necessary. If the patient has central involvement, I start anti-VEGF treatment and use the OCT to gauge the patient’s response,” says Dr. Singer. “Typically there is improvement, but the OCT also shows me patients who are not responding to anti-VEGF therapy. I divide these patients into two categories: nonresponders and inadequate responders. If a patient is still swollen after three monthly anti-VEGF injections, I give another injection and check the OCT at 2 weeks. When the OCT is dry or close to dry, it means the anti-VEGF works (the disease is still VEGF mediated), but the current choice of anti-VEGF isn’t lasting long enough. In these cases, I switch to another anti-VEGF medication. If the OCT still shows swelling and the disease is mediated by another mechanism of action (inflammation), I switch to a sustained-release steroid. By using OCT, I am able to monitor these factors and make adjustments as needed.”

While OCT remains the standard for visualizing macular edema, the technology is now applied in the promising new field of OCT angiography as well, with devices offered by Heidelberg, Optovue and Zeiss. In fact, Zeiss’s AngioPlex OCT Angiography received 510(k) clearance from FDA last month.

“We hope that by using OCT angiography to see retinal blood vessels, we’ll be able to detect early blood vessel abnormalities and identify changes related to diabetic retinopathy earlier,” says Dr. Sadda. “However, we don’t yet have the evidence to prove that it’s possible.”

Dr. Singer says, “OCT angiography is going to be the next stage of development, pulling together fluorescein angiography and OCT into a real composite image of circulation and anatomy to give us a better idea of how we’re treating diabetic patients. I think it will help us better understand how medications work on different patients so we know which patients will be more likely to benefit from various modes of therapy.

“Today, we look at patients as having the same response to treatment, but we may find that this isn’t true,” says Dr. Singer. “Some patients may be more sensitive because they have more ischemia or their disease is more inflammatory in nature. I think it will help us tailor the treatment to each patient, which would be an exciting application of this new imaging technology.” ❖

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