Welcome back to Ready, Set, Retina! In this episode, Daniel Epshtein, OD, FAAO, sits down with Julie Rodman, OD, MSc, FAAO, to review a case report of a patient with non-exudative occult choroidal neovascularization (CNV).
What is non-exudative occult CNV?
CNV is characterized by the abnormal growth of vessels from the choroidal vasculature to the neurosensory retina through Bruch’s membrane that can result in exudation, hemorrhage, and fibrosis, damaging the outer retina and often resulting in vision loss.1,2 Of note, CNV is defined as occult or type 1 choroidal neovascularization when the neovascular membrane is located below the retinal pigment epithelium (RPE).1
In the past, fluorescein angiography (FA) was the gold standard for diagnosing CNV; however, occult or type 1 choroidal neovascularization resides below the RPE, and FA generally does a poor job of imaging at this level. The borders of these lesions are poorly demarcated and absent, which are the characteristic hyperfluorescent patterns that allow for diagnosis if leakage is not present in these occult lesions.2
With the advent of optical coherence tomography angiography (OCTA), eyecare practitioners (ECPs) now have the capability of imaging retinal and choroidal microcirculation noninvasively and identifying non-exudative neovascular membranes that would be otherwise invisible with FA. This is due to the unique ability of OCTA to segment the retinal and choroidal vasculature into layers or plexi, thereby providing visualization of the vasculature at any layer.1,3
Non-exudative occult CNV case report
A 70-year-old African American male returned to the clinic 1 month after a comprehensive eye examination because he was identified as a glaucoma suspect and required further testing.
The patient’s best-corrected visual acuity (BCVA) was 20/25 OD and OS. The patient had hypertension, diabetes mellitus (DM), and acid reflux, though his systemic conditions were well-controlled.
Figures 1 and 2 are fundus photographs of the right eye (OD) and left eye (OS), respectively, at the initial visit. Enlarged cupping can be appreciated, though both images are largely unremarkable for retinal pathology.
Figure 1: Courtesy of Julie Rodman, OD, MSc, FAAO.
Figure 2: Courtesy of Julie Rodman, OD, MSc, FAAO.
OCT imaging from the glaucoma workup
Dr. Rodman then ordered OCT ganglion cell complex (GCC) and retinal nerve fiber layer (RNFL) scans as part of the glaucoma workup.
Figures 3 and 4 show OCT GCC scans OS, and a slight disorganization of the outer retina and RPE (highlighted with the red arrows) can be visualized in both scans.
Figure 3: Courtesy of Julie Rodman, OD, MSc, FAAO.
Figure 4: Courtesy of Julie Rodman, OD, MSc, FAAO.
OCT angiography
While considering the potential cause of the lesion, Dr. Rodman decided that OCTA may help narrow down the list of possible etiologies.
Figure 5 shows the results from OCTA imaging. There is a neovascular membrane at the level of the choriocapillaris (highlighted with a red circle). The lower panel is for comparative purposes and shows normal angiography images of the various plexi.
Figure 5: Courtesy of Julie Rodman, OD, MSc, FAAO.
Figure 6 is a closeup of the choroidal neovascular lesion found on OCTA.
Figure 6: Courtesy of Julie Rodman, OD, MSc, FAAO.
Follow-up
Dr. Rodman explained that she was surprised to have found a choroidal neovascular membrane, as this was her first time seeing a “dry” retina with a neovascular lesion—a departure from the typical findings associated with occult CNV from AMD.
The patient’s retinal specialist ultimately decided not to pursue further treatment because the neovascular membrane was non-exudative. As a result, she followed the patient and ordered periodic OCTA testing to monitor the CNV lesion.
Figure 6 is a multiscan view of OCTA imaging captured at follow-up visits. The CNV membrane appears to remain stable, with no signs of growth or exudation. From left to right, the OCTA images were captured on July 22, 2017, October 14, 2017, and January 13, 2018.
Figure 7: Courtesy of Julie Rodman, OD, MSc, FAAO.
Managing patients with non-exudative choroidal neovascularization
Dr. Rodman noted that in the case of this patient, due to his demographic considerations and the absence of any classic AMD signs, she initially followed up with him every 4 to 6 months to monitor the CNV lesion. However, this timeline would be altered if the patient had AMD in either eye. She also indicated that she might opt to co-manage the patient with a retinal specialist if there were other ocular co-morbidities.
She added that the risk of non-exudative neovascularization converting to the exudative form of the disease is significantly higher when the fellow eye has pre-existing AMD or neovascularization.4 In addition, she mentioned that patients with intermediate AMD and/or geographic atrophy (GA) can also develop non-exudative neovascular membranes. However, studies are finding that these membranes may, in fact, have a protective effect in GA and represent vascular remodeling.4
Dr. Epshtein added that for a patient with AMD in one eye and non-exudative occult CNV in the other, he would choose to monitor them with both structural OCT and OCTA every 2 months initially, and then extend the follow-up period to every 3 to 4 months to monitor for exudation if no changes were seen during the initial period.
Further, in his clinical experience, a telltale sign that the membrane is likely to leak is if the lesion grows. Dr. Rodman noted that, based on her experience, lesions that remain stable for longer periods of time (i.e., 6 to 12 months) are at a lower risk of exudative conversion.
Conclusion
Non-exudative CNV is a relatively new clinical entity that is now being diagnosed more frequently due to the advent of OCTA imaging.3
This case report highlights how OCTA can identify retinal microvascular changes that may possibly go undetected with funduscopy and OCT imaging.
