Solving the Diagnostic Puzzle with OCT Angiography
By Rishi P. Singh, MD
OCT angiography (OCTA) is a frequently ordered test in my practice. For patients who are already having OCT scans to assess macular edema, OCTA is simply an additional scan that is quickly accomplished with the same device. OCTA can provide information that is crucial in a differential diagnosis, and it can do so more safely and quickly than with fluorescein angiography (FA) — sometimes without any need for FA.
An apt illustration of OCTA’s usefulness is the case of a patient I recently treated: a 68-year-old female who was referred for decreased vision in the right eye. She reported having trouble seeing for 2 weeks. Her visual acuity was 20/50 OD and 20/25 OS. The only notable anterior segment finding was 2+ cortico-nuclear cataract OU. IOP was 17 mmHg in each eye. The fundus exam revealed mild hypertensive retinopathy and macular edema with hard exudates OD (Figure 1). OCT demonstrated cystoid macular edema with intraretinal fluid, hard exudates (Figure 2), and a central subfield thickness of 389 µm. Based on FA, the cause of the macular edema was not evident (Figure 3). However, OCTA demonstrated capillary nonperfusion (A), artifacts from the exudates within the retina (B), and retinal capillary remodeling (C) consistent with a branch retinal vein occlusion (BRVO) (Figure 4). In this case, OCTA alone would have been diagnostic of BRVO. The scans clearly showed vascular remodeling as well as capillary nonperfusion that was not seen on FA.
Another take-away point from this case is the need to differentiate OCTA imaging artifacts from real disease, which comes with experience. Software upgrades will eventually be very helpful in this regard, but in the meantime, utilizing OCTA more frequently is the best way to realize its benefits. In any given case, while I may ultimately decide that FA is necessary, perhaps to rule out one condition masquerading for another, I find OCTA covers most of the bases early on.
Figure 1. Mild hypertensive retinopathy and macular edema with hard exudates were noted.
Figure 2. OCT confirmed hard exudates and demonstrated cystoid macular edema with intraretinal fluid.
Figure 3. Based on fluorescein angiography, which showed macular edema and small collateral vessels (A), the cause of the macular edema remained ambiguous.
Figure 4. While artifacts appeared in the OCTA imaging (B), the scans clearly illustrated capillary nonperfusion (A) and retinal capillary remodeling (C) consistent with branch retinal vein occlusion. As such, fluorescein angiography was not necessary for determining the cause of the patient’s macular edema.
Dr. Singh is a medical director of the Clinical Systems Office at the Cleveland Clinic, a staff physician at the Cleveland Clinic Cole Eye Institute, and an associate professor of ophthalmology at Case Western Reserve University.