Overview
- Definition:
Birdshot retinochoroidopathy (BSRC) is a clinically distinct, uncommon form of posterior uveitis, characterized by vitritis, retinal vasculitis, and multiple, bilateral, hypopigmented, postequatorial inflammatory lesions at the level of RPE and choroid
Patient’s visual complaints are often out of proportion to the measured visual acuity, and fundus findings can be extremely subtle in early disease stage
- Symptoms
Floaters
Photophobia
Photopsia
Glare
Some degree of nyctalopia
Reduced contrast sensitivity
Blue-yellow dyschromatopsia and other color vision disturbances
- Laterality
Bilateral
- Course
Chronic, characterized by multiple exacerbations and remissions
Self-limited in only 20% of cases
- Age of onset
40–50 years
- Gender/race
F:M = 3:1
Almost exclusively Caucasian, with a higher incidence in those of northern European descent
- Systemic association
HLA-A29 association is perhaps most well known in ophthalmology, if not all of medicine
Though not as prevalent as HLA-A29, HLA-B44 is found in 50% of BSRC patients
Systemic hypertension appears to be more prevalent in BSRC population
Exam: Ocular
Anterior Segment
Quiet eye without conjunctival injection or ciliary flush
Mild nongranulomatous anterior uveitis (≤1+ cells) without synechia
+/− fine keratic precipitates
Normal IOP
Posterior Segment
- BSRC lesions
Multiple, cream-colored, choroidal lesions with indistinct borders, the long axis of which is radial to the optic disc scattered throughout the postequatorial retina
Round to ovoid in shape, varying in size from 50 to 1500 μm
More easily visualized clustered around the optic disc, in the inferonasal quadrant
With time, lesions may become confluent, producing large areas of geographic depigmentation
Mild-to-moderate vitritis (≤2+ haze)
Retinal vasculitis (predominantly phlebitis) typically in the absence of visible vascular sheathing
Retinal arteriolar attenuation and vascular tortuosity may be seen
CME is the most common structural complication of BSRC (cumulative incidence approaching 84% over 5 years) and is the most frequent cause of reduced central VA
ERM is common
CNV and retinal NV leading to NV are relatively rare (<10%)
Optic nerve head swelling and nerve fiber layer hemorrhages
Imaging
- FA
Macular leakage
Vasculitis (predominantly phlebitis)
Generalized abnormal hyperfluorescence
- ICG
Hypofluorescent spots and fuzzy vessels in active disease
Hypofluorescence often not seen in treated or burn-out disease
May or may not correspond to fundus lesions seen on microscopy
- Fundus autofluorescence
Abnormal in 80% of patients
Peripapillary, macular, or extramacular hypoautofluorescence
- OCT
CME and ERM
IS/OS attenuation
EDI-OCT may show choroidal lesions otherwise not apparent on ophthalmoscopy
- ERG
Early (inner retinopathy): loss of oscillatory potentials and b-wave amplitude
Late (outer retinopathy): reduction of photopic b-wave amplitude and progressive prolongation of 30 Hz implicit time (IT), used for follow up the effect of treatment
- Blue-on-yellow perimetry (SITA-SWAP)
Generalized constriction of the peripheral visual field
Central and paracentral scotomata
Enlargement of the blind spot
Abnormalities on visual field testing may occur even among minimally symptomatic patients with good VA
Laboratory Testing
- HLA-A29 phenotype
Present in 7–8% of general population
95–100% of BSRC patients
Confers 50–224 times risk of developing BSRC
Labs to rule out the masqueraders (see below)
Differential Diagnosis
Sarcoidosis
Intraocular lymphoma
VKH
Tuberculosis
Syphilis
POHS
White dot syndromes: MCP, PIC, MEWDS, APMPPE
Treatment
Periocular and systemic corticosteroids have inconsistent treatment efficacy and provide only short-term reduction in vitritis and CME, and thus should be used only for acute exacerbations
A variety of immunomodulatory agents including methotrexate, mycophenolate, cyclosporine, azathioprine, cyclophosphamide, chlorambucil, intravenous immunoglobulin (IVIg), TNF-alpha inhibitors, and anti-IL6 receptor have been employed as part of a steroid-sparing strategy in the treatment of BSRC
- We typically are following this order of therapy in the majority of our BSRC patients:
- 1.
Combination therapy of mycophenolate mofetil (1–3 g/day) and cyclosporine (100–300 mg/day)
- 2.
TNF-alpha inhibitors: infliximab 5–10 mg/kg administered every 4 weeks is very effective
- 3.Fluocinolone acetonide implant:
Higher likelihood of concurrent or subsequent glaucoma incisional surgery in BSRC patients
- 1.
Referral/Comanagement
Rheumatology