Most of the available optical coherence tomography (OCT) and OCT angiography (OCTA) devices provide clinicians with a 30-degree x 30-degree field of view. This is adequate when performing OCT and visualizing the macula. However, when OCT is performed to evaluate the changes in retinal vascular diseases, this size field of view is inadequate, according to Nadia Khalida Waheed, MD, MPH.
Increasing the field of view to evaluate those retinal vascular diseases is the next logical step. However, a number of problems become evident, Dr. Waheed pointed out. She is associate professor of ophthalmology, New England Eye Center, Tufts University School of Medicine, Boston.
For example, Dr. Waheen demonstrated that when the scanning area is increased from 3 mm x 3 mm to 6 x 6 mm and then to 8 mm x 8 mm, the loss of the fine vascular resolution is marked with each step.
There are a couple of ways to surmount this problem. One approach, she noted, is to begin with a machine that has a higher speed as in spectral-domain OCT (SD-OCT) or swept-source OCT (SS-OCT) technology. Images that are 15 mm x 9 mm and 12 mm x 12 mm obtained from SS-OCT provide good resolution of the small blood vessels, Dr. Waheed pointed out.