In the January 2019 newsletter of Ophthalmology Management, Drs. Rahul Komati and Dimitra Skondra wrote an article to describe the benefits of OCT-Angiography (OCT-A) in clinical practice.
Here are five cases where OCT-A has an advantage in diagnosing retina conditions, when compared to conventional imaging modalities:
1. Exudative AMD/CNV masqueraders. Many retinal pathologies involve macular exudation and features that mimic exudative choroidal neovascularization (CNV)/wet AMD on OCT or fluorescein angiography (FA). Some of these conditions may themselves lead to development of exudative CNV. OCTA is the most effective way to accurately diagnose exudative CNV so that it can be properly treated or to rule it out so that patients can be safely monitored without unnecessary treatment.
We recently published a case series in which patients exhibiting macular edema and/or retinal fluid were referred to us for anti-VEGF injections for treatment of wet AMD.1 In some cases, OCTA clearly showed the absence of a CNV membrane, and the patients were diagnosed with central serous retinopathy (CSR) or pattern dystrophy. Therefore, as they did not have wet AMD, none required anti-VEGF treatment, and all have remained stable with observation for up to 2 years. Another patient, who saw us for a second opinion, had been diagnosed with CSR and, based on months of observation with OCT and FA, had received no treatment. OCTA revealed a CNV membrane with associated subretinal fluid. The patient was treated with anti-VEGF injections, subretinal fluid resolved rapidly, and vision improved significantly.
2. Atypical presentations of macular diseases. Macular telangiectasia (MacTel) is a prime example of OCTA’s usefulness in this area. In the absence of classic signs, such as crystalline deposits or retinal graying, MacTel can be misdiagnosed as other conditions including macular hole, lamellar hole, epiretinal membrane (ERM), macular edema, or macular degeneration. However, OCTA can reveal microscopic vascular changes at the retinal capillary level that indicate MacTel at very early stages. When MacTel is correctly identified, we can better counsel patients for surgery or avoid surgery for conditions, such as ERM or lamellar hole, that are unlikely to improve vision. OCTA is also an extremely useful non-invasive way to identify CNV in MacTel patients, which can be missed on OCT or FA. Thus, OCTA is a valuable tool for monitoring MacTel patients so they can be appropriately treated when co-existing CNV is seen.
Proper diagnosis of MacTel is also beneficial for clinical trials evaluating novel neuroprotective treatments. OCTA helps to ensure the right types of patients are enrolled and also identifies eligible patients at earlier stages, prior to disease progression and visual loss.
3. CNV versus simple macular hemorrhage in high myopes. High myopes who present with macular hemorrhage and central scotoma raise the concern that myopic CNV has developed. A hemorrhage may obscure a CNV membrane on FA and thinning retinal layers or staphyloma could complicate OCT interpretation. Two high-myopia patients we recently evaluated illustrate how OCTA can confirm the best management course in this scenario. One patient was referred with a diagnosis of CNV requiring treatment, but OCTA confirmed the absence of active blood flow. No treatment was given, the hemorrhage eventually resolved, and vision returned to baseline. Another myopic patient was referred to us with a diagnosis of hemorrhage caused by a break in Bruch’s membrane. In this case, OCTA revealed a previously undetected small, active CNV membrane that had developed under the hemorrhage. The patient was appropriately treated with anti-VEGF injections and experienced visual improvement.
4. Occult retinal vein occlusions. We have also found OCTA to be very useful in exposing small, occult vein occlusions that are the actual culprit in macular edema labeled idiopathic or thought to be associated with an ERM. Unlike FA or OCT, OCTA clearly shows a sectoral loss of superficial and deep capillaries consistent with these old occult occlusions that present without retinal hemorrhages or obvious vascular abnormalities on exam (Figure 1). While surgery to address ERM in such a case would not improve or could worsen the condition, anti-VEGF injections are an effective treatment and can lead to resolution of edema and significant vision improvement.
5. Early subclinical CNV in AMD patients. Finally, a widely documented strength of OCTA is its ability to detect non-exudative CNV. Awareness of this type of lesion has opened an entirely new area of research aimed at determining whether closer monitoring would facilitate earlier treatment of exudative CNV in AMD patients, or whether treatment of non-exudative lesions could prevent conversion to exudation in the first place. While guidelines for optimal management in these cases are still under investigation, early diagnosis with OCTA is the first essential step for identifying these patients."
Reference (Figure 1):
Schechet S, Hariprasad SM, Mohavedan A, Skondra D. Use of optical coherence tomography angiography in masqueraders of wet age-related macular degeneration and choroidal neovascularization. Ophthalmic Surg Lasers Imaging Retina. 2018;49(2):80-85.