Case of the Year Answer

This fundus appearance is virtually pathognomonic for birdshot retinochoroidopathy.

The typical patient is Caucasian and between 40 to 60 years of age. Women are affected more than men and most cases are bilateral. Patients most commonly present complaining of floaters and decreased vision. Many individuals describe significant difficulty adapting to dark environments and poor color vision. Loss of peripheral visual field may also be described, particularly in more advanced cases. On examination, the most striking feature is the presence of numerous round or oval, depigmented, subretinal lesions located posterior to the equator. The pigmentation of the inner choroid and/or RPE in the lesions is significantly attenuated or even absent often allowing visualization of deep choroidal vessels. The spots are frequently seen near the optic nerve and may radiate into the periphery with a somewhat heavier distribution in the nasal half of the eye. Other common findings include vitritis, retinal vascular leakage, disc edema, and cystoid macular edema.

The early phase of the fluorescein angiogram is usually normal, and the hypopigmented spots seen clinically are often indistinguishable. The later phase angiogram may show some hyperfluorescence over the choroidal lesions. Leakage from the retinal vessels in the macula and periphery is common, and often causes cystoid macular edema. In many patients, fluorescence appears early in the retinal vessels only to rapidly dissipate, a phenomenon termed "quenching".

There is constriction of the peripheral visual field in one third of the cases, and a reduced electrooculogram in over half of eyes tested. The electroretinogram is frequently severely abnormal even if the electrooculogram is normal. A depressed b-wave amplitude with a normal a-wave is typical. Delayed implicit times are common on photopic studies. Some patients will also be found to have abnormalities in dark adaptation even in the absence of symptoms. Color vision is frequently abnormal and correlates with the presence of macular edema.

Birdshot retinochoroidopathy is typically a chronic condition with multiple recurrences. Later in the course of the disease the fundus lesions may coalesce leading to widespread depigmentation of the fundus. Chronic loss of vision may occur as a result of resistant macular edema and vitritis.

Steroids are frequently recommended to treat active inflammation in birdshot retinochoroidopathy, especially if CME is present. Unfortunately, most cases prove relatively resistant to treatment, while other cases respond initially to steroids but develop recurrent inflammation upon their discontinuation. Because of the complications associated with long-term use, steroids are most commonly recommended only when visually significant CME or vitritis is present. Periocular steroids may prove particularly helpful for the treatment of cystoid macular edema and avoids unwanted systemic side-effects. The use of cyclosporine in combination with other agents has been reported to result in resolution of macular edema, less vitritis, improved vision, and fewer recurrences. Unfortunately, in spite of therapy, most patients experience visual loss to 20/200 or worse in at least one eye.

The cause of birdshot retinochoroidopathy is unknown. HLA-A29 has been found to be present in up to 95 percent of cases suggesting a strong immunogenetic predisposition to this disease.