OCTA brings understanding to managing diabetic eye disease

August 9, 2017

Optical coherence tomography angiography (OCTA) is a promising new approach for visualizing retinal vascular pathology in eyes with diabetic eye disease that can be expected to have even greater utility in the future pending further enhancements.

Optical coherence tomography angiography (OCTA) is a promising new approach for visualizing retinal vascular pathology in eyes with diabetic eye disease that can be expected to have even greater utility in the future pending further enhancements.

“Compared with fluorescein angiography, OCTA is a faster and noninvasive imaging technique performed without the need for injecting dye, and it allows for correlation of structure to vasculature,” said Nadia K Waheed, MD, MPH. “However, enhancements are needed to allow for better evaluation of blood flow and true widefield imaging.

Dr. Waheed is associate professor of ophthalmology, New England Eye Center, Tufts University Medical Center, Boston.

Discussing the use of OCTA for the evaluation of patients with diabetic eye disease, Dr. Waheed explained that the fully mature retinal circulation at the macula is probably comprised of four different plexuses that are typically subdivided as being superficial and deep based on their location relevant to the inner plexiform layer. Fluorescein angiography primarily images only the superficial retinal plexus, whereas the deep vasculature can also be visualized using OCTA.

“Because OCTA is a depth-resolved imaging technique, it has the advantage compared with fluorescein angiography of separating the superficial and the deep vasculature,” Dr. Waheed explained. “This feature has relevance in patients with diabetes because the deep vasculature tends to be affected earlier in patients who develop diabetic eye disease.”

In the few years since OCTA was introduced, it has shown to enable better visualization of capillary abnormalities in eyes with diabetic retinopathy, allowing the identification of changes in the deep plexus that are not evident on fluorescein angiography.

“Diabetic vasculopathy typically develops much sooner than diabetic retinopathy becomes clinically apparent,” Dr. Waheed said. “Using OCTA in patients with diabetes and clinical evidence of diabetic retinopathy, we found that they not only had changes in their retinal vasculature but also had a diabetic choroidopathy.”

The vascular abnormalities also can be mapped and quantified using OCTA. By doing so, researchers have described changes in the foveal avascular zone, perfusion, and arborization of the vascular network at the macula that are commensurate with the severity of diabetic retinopathy.

“In the future, commercially available OCTA systems will have software modules for monitoring patients over time based on quantification of these deteriorations,” Dr. Waheed added. 

Application in clinical care

In routine practice, the focus of follow-up by retina specialists in patients with diabetes includes evaluation for worsening of diabetic retinopathy and for the development of macular edema, macular ischemia, and neovascularization. In addition, widefield imaging may be used to identify nonperfusion in the periphery.

Dr. Waheed said OCTA enables early visualization of diabetic vascular changes in the eye and their quantification, thereby allowing better follow-up over time. Its ability to characterize the deep capillary plexus also has ramifications for patient care since changes in the deep vasculature have been shown to be associated with the evolution of diabetic macular edema (DME).

“Increasing development of microaneurysms in the deep capillary plexus has been shown to be predictive of DME development and potentially of recurrence after response to anti-VEGF treatment for DME,” Dr. Waheed said.

In addition, OCTA allows precise correlation of structure to vasculature that can help with understanding clinical status. Discussing a patient being treated for DME, Dr. Waheed noted that while the macular edema resolved with anti-VEGF therapy and the patient’s vision improved, visual acuity plateaued at 20/40.

“OCTA showed the presence of ischemia that provided an explanation for the vision outcome that could not be determined with the structural OCT alone,” Dr. Waheed said.

In addition, OCTA allows precise monitoring of proliferative diabetic retinopathy as it can be used to map out the size of the neovascular network. However, OCTA has a limited field of view.

“The central images with OCTA are of much higher resolution than those obtained with fluorescein angiography,” Dr. Waheed said. “OCTA does not allow for evaluation of peripheral areas of nonperfusion as can fluorescein angiography.”

 

Nadia Waheed, MD, MPH

P: 617-636-7950

E: nadiakwaheed@gmail.com

This article is based on a presentation delivered by Dr. Waheed at the 2017 Retina World Congress.