Use of En Face Swept-Source Optical Coherence Tomography Angiography in Identifying Choroidal Flow Voids in 3 Patients With Birdshot Chorioretinopathy

Abstract

Importance: Patients with birdshot chorioretinopathy (BSCR) can experience a delay in diagnosis owing to the challenges of identifying the condition prior to evolution of characteristic choroidal scars. An objective, noninvasive method for detecting early lesions in BSCR might have an effect on preventing vision loss in these patients.

Objective: To test the feasibility of swept-source optical coherence tomography angiography (SS-OCTA) in the detection of BSCR choroidal lesions and to use en face image analysis of choroidal layers to localize lesion depth.

Design, setting, and participants: Prospective, longitudinal, observational case series of 3 patients diagnosed as having BSCR at 1 of 2 tertiary care uveitis centers between August 2017 and October 2017.

Exposures: Widefield SS-OCTA and indocyanine green angiography (ICGA).

Main outcomes and measures: En face SS-OCTA slabs through the choroid were evaluated for the presence of flow voids corresponding to hypocyanescent lesions by ICGA. Baseline and posttreatment images were compared.

Results: Six eyes of 3 patients with previously undiagnosed and untreated BSCR were imaged at baseline and after initiation of immune modulation treatment. Two patients had a history of recent-onset BSCR, and the third patient had a history of chronic untreated disease of at least 5 years' duration. All patients were white and between the ages of 50 and 67 years. All eyes demonstrated multiple flow voids on en face SS-OCTA images that corresponded with hypocyanescent lesions by ICGA. Analysis of serial depth en face SS-OCTA flow images identified that in the acute-onset patients, flow voids were located adjacent to large vessels in the Haller layer and regressed with treatment. In the patient with chronic, untreated disease, full-thickness choroidal flow voids were identified that did not regress with treatment.

Conclusions and relevance: For these 3 patients, SS-OCTA provided a noninvasive method for identifying early BSCR lesions previously visible only with ICGA. The depth information provided by SS-OCTA suggests acute lesions originate in the Haller layer, and that in the absence of treatment, damage extends up thorough the superficial choroid, and ultimately to the retinal pigment epithelium and retina. Swept-source OCTA may represent a new and noninvasive method for detecting and monitoring disease activity in BSCR.

Figure 1.. Identification of Choroidal Flow Voids Corresponding to Indocyanine Green Angiography (ICGA) Lesions via Swept-Source Optical Coherence Tomography Angiography (SS-OCTA)

A, Indocyanine green angiography at presentation with hypocyanescent choroidal lesions (patient 1). Nevus (white arrowhead) indicates SS-OCTA boundary (boxed). B, The deep choroidal en face slab identifies flow voids corresponding to ICGA lesions. C, ICGA after oral corticosteroid treatment. D, Choroidal en face slab with regression of flow voids after treatment.

Figure 2.. Localization of Flow Voids In Active Disease to Haller Layer in the Deep Choroid

Serial en face slabs were generated for analysis from progressively deeper choroidal layers. A, Choriocapillaris. B, Sattler layer. C, Haller layer. In acute disease, flow voids (white arrowheads) localize to the deep choroid. D, After corticosteroid treatment, flow voids regress. Scale bar represents 1 mm.

Figure 3.. Presence of Flow Voids in Chronic Disease in All Layers of the Choroid

A, Full-thickness choroidal swept-source optical coherence tomography angiography (SS-OCTA) en face image in chronic birdshot chorioretinopathy (BSCR) (patient 3). These chronic birdshot lesions demonstrate flow voids by SS-OCTA through all layers. B, Choriocapillaris. C, Sattler layer. D, Haller layer. Scale bar represents 1 mm.