Birdshot Chorioretinopathy Details

Expanded Description

Birdshot Chorioretinopathy is a well-known, yet poorly understood, form of posterior uveitis, characterized by multiple, distinctive, hypopigmented choroidal lesions, and strongly associated with human leukocyte antigen (HLA)-A29.

Prevalence

No prevalence information has been added yet.

Causes

The cause of Birdshot Chorioretinopathy is unknown. It is thought to be an autoimmune condition and seems to mainly affect people who carry the HLA A29 antigen. It is possibly caused by an environmental trigger.

Disorder Symptoms

There are several symptoms that affect patients with Birdshot Chorioretinopathy.

Name	Description
Decreased vision	Decreased vision occurs in about 68% of patients
Floaters	Floaters occur in about 29% of patients
Nyctalopia	Nyctalopia occurs in about 15% of patients
Dyschromatopsia	Dyschromatopsia occurs in about 12% of patients
Glare	Glare occurs in about 19% of patients
Photopsia	Photopsia occurs in about 17% of patients
Fluctuating vision	Fluctuating vision occurs in about 7% of patients
Pain	Pain occurs in about 7% of patients
Decreases depth of perception	Decreases depth of perception occurs in about 5% of patients
Shimmering vision	Shimmering vision occurs in about 3% of patients
Metamorphopsia	Metamorphopsia occurs in about 3% of patients
Decreased peripheral vision	Decreased peripheral vision occurs in about 3% of patients

Diagnosis

Patients may present with complaints of severe nyctalopia despite normal Snellen visual acuity. Other reported presenting symptoms included glare, photopsia, photophobia, fluctuating vision, decreased peripheral vision, metamorphopsia, and decreased depth perception. 28,29,68,76 Symptoms can precede the onset of the classic depigmented spots in the fundus by several years.

Diagnostic Tests

Blood testing for HLA-A29 helps to support the diagnosis, but not all patients with Birdshot Chorioretinopathy are HLA-A29 positive. 7% of the Caucasian population are HLA A29 positive, 95% of Birdshot Chorioretinopathy patients are HLA A29 positive.

Other diagnostic tests are used to determine the extent of the choroid and retinal deterioration, including:

Electroretinograph (ERG): measures the retinal function of the eye and considered to be a required test for all Birdshot Chorioretinopathy patients; preferably minimum of every 6 months for active flares

Multifocal ERG (mfERG): new version of the ERG, very well suited for patients with poor vision but normal-looking retina

Field Tests (mainly for peripheral vision): method of measuring an individual’s entire scope of vision, that is their central and peripheral (side) vision

Fluorscein angiography: uses an special dye and camera to evaluate the blood circulation in the retina and choroid

Indocyanine green angiography (ICG): uses Indocyanine green dye which fluoresces in the infra-red (non-visible) light. The infra-red wavelengths have the ability to penetrate the retinal layers making the circulation in deeper layers visible when photographed with an infra-red sensitive camera. Typically used in conjunction with fluorscein angiography

Optical Coherence Test (OCT): device that uses sound waves to provide detailed retinal images

Name
HLA A29

Disorder Treatments

The appropriate level of treatment is determined by the severity of the inflammation. Conflicting reports exist regarding the efficacy of steroids. Some patients with mild inflammation may respond well to regional injection of steroids. Other patients require the use of systemic prednisone for control of the inflammation. Some patients may be controlled on less than 10 mg/d, while other patients require higher doses. Long-term treatment, even 10 mg/d of steroids, is undesirable, considering the high risk of significant morbidity and mortality of such treatment. Many patients show no significant response to steroid therapy.

Cyclosporine has been shown to have a beneficial effect on Birdshot Chorioretinopathy inflammation in retrospective case series. Initial reports demonstrated improved visual acuity, decreased vitritis, and stabilization of eyes with cyclosporine dosages of 10 mg/kg/d. However, this dose also was associated with a high incidence of nephrotoxicity and hypertension. Vitale and colleagues reported a series of 19 cases of Birdshot Chorioretinopathy, which demonstrated that cyclosporine treatment with lower dosages, from 2.5-5 mg/kg, can be effective.7 This series showed control of vitreal inflammation in 88.5% of eyes and improved or stable visual acuity in 83.3% of eyes. However, the low incidence of drug toxicity was most striking; there were only 2 cases of hypertension and no cases of nephrotoxicity.

One suggestion is to initially start cyclosporine dosages at 2.5 mg/kg and then to increase to the level necessary to control the inflammation, while ensuring avoidance of drug adverse effects. The maximum dosage is 5 mg/kg according to this author. Monitoring for blood counts and renal function is performed every 4-6 weeks, along with blood pressure monitoring. Cyclosporine serum levels are not followed at these dosing regimens. Other potential adverse effects, such as hirsutism, paresthesias, tremor, and gingival hyperplasia, are not risks for morbidity, but are mentioned, since lowering of drug dosage or discontinuation of the medication may be indicated if such adverse effects occur to a point of affecting the quality of the patient’s life.

One study reports the use of ketoconazole as adjunct therapy to cyclosporine. Ketoconazole delays metabolism of cyclosporine; hence, it may lower the dose of cyclosporine required to maintain control of inflammation. Silverstein and Wong demonstrated that cyclosporine trough levels could be maintained in a patient when the cyclosporine dosage was dropped from 200 mg/d (3 mg/kg) to 50 mg/d (0.75 mg/kg) with the addition of ketoconazole at 200 mg/d. This amounts to an 80% reduction of cyclosporine consumption. While this may be cost-saving, one cannot necessarily equate stabilization of cyclosporine serum levels with adequate control of inflammation nor with reduced potential toxicity. After all, the serum cyclosporine levels are still in the therapeutic range, and one might expect cyclosporine toxicity prevalence to be unchanged. Additionally, ketoconazole is not without potential adverse effects, especially the risk of hepatitis.

Other immunomodulatory therapies have been described. Kiss and colleagues reported the use of mycophenolate mofetil, azathioprine, methotrexate, and daclizumab in a series of 28 patients with Birdshot Chorioretinopathy; however, the small size of the study precludes any comment on the efficacy of any single drug. LeHoang and colleagues reported the use of intravenous immunoglobulin in a series of 18 patients as initial therapy for active birdshot retinochoroidopathy, and they noted stable vision in 33 of 36 eyes over a mean follow-up period of 39 months.

Name
Systemic Prednisone

Prognosis

Birdshot Chorioretinopathy is a chronic disease that is characterized by multiple exacerbations and remissions. Birdshot Chorioretinopathy tends to stabilize over a 3- to 4-year period, however, greater than one third of patients reach a visual acuity of 20/200 or worse. Visual loss is most commonly the result of cystoid macular edema and optic nerve atrophy.

One series described deterioration on ERG and visual field or significant visual morbidity in 10 of 15 patients during follow-up. Of note, most patients in the series either had no treatment or treatment with steroids alone (ie, no immunomodulatory therapy).

If uncontrolled, Birdshot Chorioretinopathy usually has a progressive course, with significant ocular morbidity as the consequences.

Complications from Birdshot Chorioretinopathy include:

1.) Chronic cystoid macular edema – 50%; the most common cause of reduced central visual acuity
2.) Epiretinal membrane – 10%
3.) Macular pucker
4.) Choroidal neovascularization
5.) Peripapillary subretinal neovascularization – 6%
6.) Retinal neovascularization located on the optic disc
7.) Peripheral retinal neovascularization with capillary nonperfusion
8.) Optic nerve atrophy

Other complications, such as cataract, glaucoma and rhegmatogenous retinal detachment can occur as well.

Tips for Living with the Disorder

We don't have any tips yet.