Conditions

What is Birdshot?

Birdshot retinochoroiditis (BRC) is an uncommon, chronic, progressive, sight-threatening form of uveitis.

The disease is more frequent in the middle-aged Caucasian population with female predominance.

BRC affects both retinal vessels and choroid, and is usually bilateral.

The presence of multiple, creamy-coloured lesions, scattered in the posterior pole, produced the typical ‘Birdshot’ appearance that gave the disease its name (figure).

The inflammation of retinal vessels is responsible for shedding inflammatory debris into the vitreous, resulting in vitreous opacifications.

What causes Birdshot?

Birdshot is an inflammatory condition limited to the eye driven by an abnormal immune response that occurs in genetically predisposed individuals.

All patients present a marker in their white blood cells known as human leukocyte antigen (HLA)-A29.

What are the symptoms?

Symptoms include

Visual acuity is often preserved at least in the early stages. With the progression of the disease the visual loss becomes more apparent and central vision also gets gradually affected.

Birdshot does not manifest with pain or eye redness.

Diagnosis

The clinical presentation with typical Birdshot lesions and the presence of HLA-A29 are usually sufficient to confirm the diagnosis.

Other tests frequently carried out are the dye tests, including fundus fluorescein angiography and indocyanine green angiography, which are important in detecting inflammation of the retinal vessels and choroidal lesions, and to monitor the course of the disease and its response to treatment.

The retinal function can also be measured by special tests, including visual fields and electrodiagnostic tests.

Treatment

The intention of therapy is to control the inflammation and prevent the damage to the retina, and consequently the visual loss.

The treatments are not curative but aim at controlling the immune response which is the reason of the inflammatory reaction in the eye.

Options include the use of oral medications, usually starting with systemic steroids to induce rapid response. In view of the nature of the disease, the addition of immunosuppressive drugs is important to allow long term control and minimize the side effects of the steroids.

Local therapy has been explored and includes the use of steroid devices (Ozurdex and Iluvien).

The local therapy alone may not be sufficient to control all the manifestations of the disease and the recommendation is to combined local treatment with oral medications, which can thus be used at lower level.

Complications and Prognosis

If not well controlled, BRC can result in long term damage because of the chronic macular oedema and loss of retinal tissue.

Other less common complications include abnormal vessels growing under the retina (choroidal neovascularization) and epiretinal membrane.

All these complications can affect the quality of vision.

Multimodal imaging of Birdshot retinochoroiditis.

Optos colour images showing multiple, creamy-coloured lesions, scattered in the posterior pole, producing the typical ‘Birdshot’ appearance which gave the disease its name.

Optos angiography images showing inflammation at the level of the retina and choroid. Optical coherence tomography (OCT) images showing bilateral accumulation of fluid in the retina (macular oedema).

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