Sunir J. Garg, MD, FACS
• Chronic, bilateral, posterior uveitis
• The characteristic lesions are yellow-white spots at the level of choroid that “radiate” from the disk.
• Over 90% of patients are HLA-A29 positive.
Very rare eye disease
• In the population, it affects <1/200,000.
• It affects 1% of patients in uveitis clinics and 5–7% of all patients with posterior uveitis.
• Most common in Caucasian patients
• Equal male/female distribution
• Mean age of onset ∼50 years old
• No strong familial association (although disease has been reported in monozygotic twins)
• Very strong association with HLA-A29 allele (birdshot has the highest association between HLA class I alleles and any disease)
• 90% of patients with disease have HLA-A29 compared with 7% of general population.
• Likely autoimmune process
• Some similarities between birdshot and murine models of retinal S-antigen-induced uveitis
Autoimmunity, likely involving type IV hypersensitivity
COMMONLY ASSOCIATED CONDITIONS
• Gradual, painless vision loss
• Floaters are common.
• Symptoms are usually bilateral.
• Nyctalopia, peripheral visual field constriction, abnormal color vision, photopsias, and photophobia may also occur.
• The eyes are usually painless and appear white and noninflamed.
• The anterior segment has no to mild inflammation.
• A mild to moderate diffuse vitreitis is common.
• The characteristic lesions are cream colored hypopigmented spots in the choroid with relatively indistinct borders.
• These lesions are suggestive of scattering of “birdshot” from a shotgun.
• The choroidal spots occasionally may not appear until later in the disease.
• Cystoid macular edema (CME) is a common cause of decreased visual acuity.
• Retinal vasculitis involving veins and capillaries is sometimes seen, as is optic disk edema.
DIAGNOSTIC TESTS & INTERPRETATION
• None are absolutely required for diagnosis; however, HLA-A29 is a reliable marker of disease (∼95% specificity and sensitivity).
• Must rule out other treatable causes of posterior uveitis, including syphilis, tuberculosis, lyme disease, ocular lymphoma, and sarcoidosis.
• Fluorescein angiography (FA) shows early hypofluorescence and late hyperfluorescence of choroidal lesions, as well as hyperfluorescence of the disk, vascular leakage, and CME (when present).
• Indocyanine green angiography (ICGA) often demonstrates more lesions than seen on either clinical exam or FA. ICG shows early hypofluorescence of choroidal lesions.
• Optical coherence tomography (OCT) can be useful to detect macular edema.
• Electroretinograms (ERG) are often abnormal, typically showing a decrease in both photopic and scotopic amplitudes; B-wave may be affected more than A-wave initially.
• Peripheral visual field testing may show constriction.
Follow-up & special considerations
• FA useful to monitor amount of inflammation and to follow response to therapy
• OCT useful to evaluate patients for macular edema, and for evaluating response to treatment
There are limited reports in the literature; however, lymphocytic aggregates in the choroid and retinal vasculature have been noted.
• White dot syndromes (acute posterior multifocal placoid pigment epitheliopathy, multifocal choroiditis and panuveitis, multiple evanescent white dot syndrome)
• Infectious posterior uveitis (tuberculosis, syphilis, and presumed ocular histoplasmosis syndrome)
• Masquerade syndromes (leukemia and ocular lymphoma)
• Ocular and systemic steroids have been the mainstay of therapy; however, the typical chronicity of this disease warrants consideration of nonsteroidal immunomodulatory therapy early in the disease course.
• Dramatic improvement of ocular inflammation can often be seen with systemic steroids (prednisone 1 mg/kg per day); however, long-term toxicity of steroids limits this approach.
• Cyclosporine, mycophenolate mofetil, azathioprine, cyclophosphamide, and methotrexate have all been used as nonsteroidal immunomodulatory therapies.
• Periocular and intravitreal triamcinolone acetate has been used to treat severe inflammation and/or macular edema.
• More recently, use of antitumor necrosis factor alpha drugs and intravenous immunoglobulin has been reported.
Issues for Referral
• Management of birdshot retinochoroidopathy often requires referral to a uveitis and/or retina specialist.
• Consultation with a rheumatologist or hematologist may be required when immunomodulatory agents are used.
• As with other types of ocular inflammation, cataract formation may be accelerated in patients with birdshot; cataract surgery is best delayed until the patient is free of inflammation for at least 3 months.
• Glaucoma filtration or shunting surgery may be required in some patients with uncontrolled glaucoma.
• In the near future, implantable drug delivery devices may play a major role in the treatment of this disease.
Pulse intravenous steroids may be considered in severe cases with profound bilateral vision loss.
The course of birdshot is often progressive over a number of years, with intermittent exacerbations of disease activity; therefore, patients should be monitored closely by a specialist familiar with the treatment of the disease.
• Visual acuity may be normal until late in the disease course.
• Careful biomicroscopic examination should be undertaken at regular intervals.
• Ancillary testing such as FA, ICGA, OCT, peripheral visual field testing and ERG testing should also be taken at regular intervals to monitor disease activity.
• Patients should be aware of the chronic progressive nature of birdshot chorioretinopathy, and the associated need for close monitoring and long-term treatment of the disease.
• Patients should also be aware that a variety of immunomodulatory treatments are available, and not be discouraged if one treatment modality is insufficient to treat their disease.
• Because of the chronic progressive nature of the disease, visual prognosis is guarded over time.
• Patients often need to be treated with immunomodulatory agents that have side effects.
• Visual function can often be impaired to a greater extent than the visual acuity indicates.
• CME is the most common cause of decreased visual acuity.
• Epiretinal membranes (ERM) are also common.
• Glaucoma may be seen in up to 20% of patients and is likely a secondary effect from systemic and ocular steroid treatments.
• Choroidal neovascular membranes (CNVM) can occur in areas of chronic choroidal inflammation.
• Retinal neovascularization is uncommon, but can result from retinal vascular inflammation and secondary retinal ischemia.
• Optic nerve atrophy is rare, but has been reported.
• Ryan SJ, Maumenee AE. Birdshot retinochoroido-pathy. Am J Ophthalmol 1980;89(1):31–45.
• Jap A, Chee SP. Immunosuppressive therapy for ocular diseases. Curr Opin Ophthalmol 2008;19(6):535–540.
• Monnet D, Brézin AP. Birdshot chorioretinopathy. Curr Opin Ophthalmol 2006;17(6):545–550.
• Kiss S, Anzaar F, Foster SC. Birdshot retinochoroido-pathy. Int Ophthalmol Clin 2006;46(2):39–55.
• Shah KH, Levinson RD, Yu F, et al. Birdshot chorioretinopathy. Surv Ophthalmol 2005;50(6):519–541.
363.20 Chorioretinitis, unspecified
• Chronic, progressive, bilateral posterior uveitis
• Characteristic peripapillary choroidal lesions and associated vitreitis are usually present.
• Very strong association with HLA-A29
• Common cause of decreased visual acuity is cystoid macular edema.
• Electroretinograms are usually abnormal.
• Patients are often initially responsive to steroids but often require maintenance with nonsteroidal immunomodulatory agents.