Autoimmune diseases are quite distinct from inherited retinal dystrophies. In Autoimmune Retinopathy (AIR) the body’s own defence mechanism starts attacking tissues by mistake, in this case the retina, as opposed to in a genetic condition like inherited sight loss which leads to retinal degeneration.
Upon learning of treatments for and research into AIR, and considering their symptoms, some people with an inherited retinal dystrophy may become concerned they have been misdiagnosed and that unlike in the case of inherited sight loss, they have a condition where an unproven treatment can be offered.
In fact, AIR generally has a much later onset than inherited sight loss and will not be familial; a blood test for antibodies against retinal proteins would suggest AIR as described above. If you have been given a genetic diagnosis of an inherited retinal dystrophy the diagnosis has already been made.
In addition, any treatments for AIR are not translatable between these two very different groups of conditions.
If you have any concerns about your diagnosis, you should seek the advice of your retinal specialist for expert advice.
What is AIR?
Autoimmune retinopathy (AIR) is a term given for patients who have a rare autoimmune condition that results in loss of photoreceptor (rods and cones) function. The immune system protects us against infection, cancer and damaged cells. The orchestrators of the immune system are our white blood cells that are rapid in their response to insults and part of their role is to remove the ‘danger’. To do this a subset of white blood cells called B cells produce antibodies (immunoglobulins) that attack the infection or damaged cells. However, sometimes the immune system is unable to differentiate between its own proteins on the surface of cells from foreign protein (e.g. an infection). When this happens conditions called autoimmune diseases may prevail, and AIR is thought to be an example of such an autoimmune disease.
How does AIR present?
The condition can be slow and relentless with respect to symptoms and presentation. Often AIR is characterised by initial visual field defects and episodic flashing lights (photopsia) and night blindness (nyctalopia) resulting potentially in significant vision loss. To the doctor the appearance of the eye can look normal for some time and in particular the retina (fundoscopy) is healthy looking, initially. Later in disease there can be loss of retinal pigment epithelium or pigmentary changes at the macular of the retina and retinal tissue loss (atrophy) and very late in disease the retinal vessels are thinned and the optic nerve head (optic disc) has a waxy pale appearance.
How is AIR diagnosed?
While there are variances in the presentation and ocular appearance during the presentation and course of AIR, the diagnosis is based on the presence of circulating auto-retinal antibodies which target retinal antibodies and are thought to cause the loss of photoreceptors. There remains no international consensus on diagnostic criteria.
Autoretinal antibodies are detected by specialised laboratories using techniques knows as ELISA and Western blot and immunohistochemistry and patients may have more than anti-retinal antibody. However, the presence of autoantibodies is not diagnostic.
Other ancillary tests may help the clinician make diagnosis including characteristic electrodiagnostic features seen in AIR (testing the electrical function of the retina), and characteristic features on enhanced imaging of the retina.
How is AIR treated?
There is no clear guidance on best treatment options. In general most specialists choose to treat with drugs or agent that suppress the immune system (called immunomodulation) but at best remains empiric in choice of drug. Such drugs include (and not exclusively): Steroids, mycophenolate mofetil, targeted B cells therapy (Rituximab) and intravenous immunoglobulin therapy (IVIG).