Pilot Study of OCT Versus Fluorescein Angiography in DME

Diabetic macular edema (DME) is one of the most common causes of visual loss in patients with diabetes and a leading cause of blindness in the working age population.

In DME, excess fluid from blood vessels in the retina leaks into the macula, causing swelling. Because the macula is responsible for sharp central vision, the swelling causes blurred or distorted of central vision, loss of contrast sensitivity, and can include changes in color perception. A patient with macular edema may or may not also have ischemia, an abnormal reduction in blood flow to the retina due to blockage of the retinal blood vessels. In macular ischemia, inadequate blood supply to the central retina results in a loss of retinal cell function and irreversible central vision loss. DME is most often treated with a focal laser application or an injection of an anti-vascular endothelial growth factor (anti-VEGF) drug into the eye to stop leaky vessels.

DME is currently diagnosed by slit-lamp biomicroscopy and optical coherence tomography (OCT). Conventionally, OCT is used to assess edema (retinal thickening and fluid pockets). The initial assessment and treatment planning also requires an assessment of macular perfusion, which is currently done by fluorescein angiography (FA). FA is used to identify microaneurysms and areas of capillary dropout (ischemia), which guides focal laser treatment and helps predict treatment response. Eyes with greater ischemia respond more poorly to treatment. FA requires the injection of sodium fluorescein into the systemic circulation. However, 1 in 3 people have adverse reactions to sodium fluorescein, which can include nausea, vomiting, hives, and acute hypotension. Severe reactions such as anaphylaxis, causing cardiac arrest and sudden death due to anaphylactic shock, have also been reported. Finally, because the risks of sodium fluorescein to a developing fetus are unknown, its use in pregnant women is contraindicated. Replacing FA with a less invasive and better tolerated method would reduce the risk in the patient population. One option is OCT angiography.

Optical coherence tomography is an imaging technology that can perform non-contact cross-sectional imaging of tissue structure in real time.It is analogous to ultrasound B-mode imaging, except that OCT measures the intensity of reflected light rather than acoustical waves. OCT has a number of features that make it attractive as a diagnostic imaging modality: 1.) It has micron-level resolution, which is not possible with any other non-contact technique; 2.) No potentially allergenic dyes or contrast agents are required; 3.) OCT images are generated in electronic form, which facilitates the use of digital image processing techniques to extract quantitative parameters regarding the imaged tissue anatomy. For these reasons, structural OCT is already routinely used to assess areas of macular edema and response to treatment. Novel functional OCT including Doppler OCT and OCT angiography may allow an assessment of retinal blood flow and obviate the need for the more invasive FA test.

Thus, if the diagnostic data provided by functional OCT are at least equivalent or superior to those achieved by FA, patients and healthcare providers could realize a substantial benefit in utilizing this technology in the management of DME. To clarify, FA is standard of care and is not a procedure in this protocol, rather simply a comparison is being conducted between functional OCT and FA.