Birdshot Chorioretinopathy affects between 0.6 and 1.5 percent of the population. The disease is more common in North European descents with a female preponderance which is 1 in 2000. It accounts for 6%-8% of cases of posterior uveitis. Prevalence in US is 1 in 200,000.  In North Carolina, it is estimated to be 1 in 700,000. The condition typically occurs in the Caucasian population aged 35-70 years, with the average age of diagnosis at 50 years.

The cause for Birdshot Chorioretinopathy has not been confirmed; however, it is believed that the condition is related to inherited retinal autoimmunity dysfunction. There is a strong link of the condition to the presence of the human leukocyte antigen A29 (HLA-A29) molecule. Positivity for the HLA-B12 antigen may also be linked to Birdshot Chorioretinopathy, although this causation has not been confirmed.

There are several symptoms that affect patients with Birdshot Chorioretinopathy. Patients may present with complaints of severe nyctalopia or inability to see in dim light. Other reported presenting symptoms included glare, photopsia, photophobia or seeing flashes of light, fluctuating vision, decreased peripheral vision, decreased depth perception, and metamorphopsia. Metamorphopsia is a condition where straight lines appear curvy. 

The most common test for diagnosis of Birdshot Chorioretinopathy after examination in the eye clinic is the human leukocyte antigen (HLA) test. Electroretinograms which measure electrical responses by the various cells of the retina may also be carried out. Patients with Birdshot Chorioretinopathy will show diminished responses in the electroretinogram tests. Biopsies may be performed to verify diagnoses.

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.

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.