Features
Birdshot retinochoroiditis (BRC), also referred to as birdshot chorioretinopathy, is a chronic uveitic condition affecting the retina, retinal pigment epithelium (RPE), and choroid. The etiology of BRC is unclear, though there is a strong association with human leukocyte antigen (HLA)-A29, which is positive in over 95% of patients with BRC.
67.1.1 Common Symptoms
Floaters, photopsias, blurry vision, nyctalopia, dyschromatopsia, and/or photophobia.
67.1.2 Exam Findings
Diagnostic criteria for BRC are summarized in ▶ Table 67.1. Typically, there is a variable low-grade anterior chamber inflammation. Findings such as keratic precipitates or posterior synechiae should prompt suspicion for an alternate diagnosis. Additional findings include anterior vitreous cells, mild to moderate vitreous haze, and bilateral cream-colored ovoid choroidal lesions with indistinct borders (▶ Fig. 67.1). The choroidal lesions are usually about 500 to 1,500 μm in diameter and their long axes are oriented radial from the optic nerve head. The choroidal lesions are most often located in the peripapillary retina and tend to be more numerous nasally and inferiorly. With time, these lesions may coalesce in a linear pattern along retinal veins. Additional variably present findings include optic nerve swelling, epiretinal membrane (ERM), cystoid macular edema (CME), choroidal neovascularization (CNV), perivenous sheathing, and retinal neovascularization. Late changes include optic atrophy, vascular attenuation, macular scar formation, and chorioretinal atrophy (▶ Fig. 67.2). Patients may have symptoms for years prior to the development of typical birdshot lesions. In such cases, ancillary testing may be critical for diagnosing BRC.
Required characteristics |
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Supportive findings |
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Exclusion criteria |
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Abbreviations: HLA, human leukocyte antigen; UCLA, University of California, Los Angeles. | |
Fig. 67.1 Ultra-widefield color photograph showing widespread depigmented lesions in birdshot retinochoroiditis.
Fig. 67.2 (a) Color fundus photograph of birdshot retinochoroiditis at presentation and (b) 8 years later, showing interval development of numerous additional depigmented lesions in the macula and areas of chorioretinal atrophy nasal to the disc.
67.2 Key Diagnostic Tests and Findings
67.2.1 Optical Coherence Tomography
Possible findings on optical coherence tomography (OCT) include CME, ERM, and/or changes associated with CNV formation such as intraretinal fluid, subretinal fluid, and subretinal hyperreflective material. Advanced cases may show outer retinal layer disruption and/or chorioretinal atrophy. Enhanced depth imaging OCT can help identify choroidal lesions, which may appear as focal or diffuse areas of hyporeflectivity.
67.2.2 Fluorescein Angiography or Ultra-Widefield Fluorescein Angiography
Venous leakage, papillitis, CME, CNV, and rarely retinal neovascularization can be identified based on leakage patterns (▶ Fig. 67.3). Birdshot lesions are not usually highlighted on fluorescein angiography, although advanced lesions may be hyperfluorescent secondary to a window defect or staining. “Quenching” may appear wherein dye disappears from the retinal circulation more rapidly than normal.
Fig. 67.3 Multimodal imaging and functional testing to assess disease activity in birdshot retinochoroiditis. (a) Fluorescein angiography in an eye with birdshot, showing hyperfluorescence/leakage at the disc and along the vessels and petaloid leakage in the macula. (b) Humphrey visual field of the left eye of a patient with birdshot, showing peripheral visual field loss.
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