Autoimmune retinopathy is a rare eye condition where the body’s immune system mistakenly attacks the retina, the light-sensitive tissue at the back of the eye. This erroneous immune response can lead to progressive vision loss.
What is Autoimmune Retinopathy?
Autoimmune retinopathy (AIR) is a rare immunological disease where the body’s immune system misidentifies healthy retinal cells as threats and attacks them. This assault targets proteins within the retina, leading to vision loss. The underlying reasons for this autoimmune attack are not fully understood, but it is believed to involve molecular mimicry. This occurs when foreign antigens, such as those from viruses or bacteria, share a similar sequence with the body’s own retinal proteins, causing the immune system to react against both.
AIR is categorized into two main classifications: Cancer-Associated Retinopathy (CAR) and Non-Cancer-Associated Autoimmune Retinopathy (nAAR). CAR is a paraneoplastic syndrome, triggered by an immune system response to a cancer elsewhere in the body. In CAR, tumor antigens can cross-react with retinal proteins, prompting the immune system to attack the retina. Common cancers associated with CAR include small cell lung carcinoma, breast cancer, and gynecologic cancers.
Non-Cancer-Associated Autoimmune Retinopathy (nAAR) is not linked to an underlying malignancy. In these cases, molecular mimicry might occur between retinal proteins and antigens from presumed infections, such as viruses or bacteria. Both CAR and nAAR can lead to retinal degeneration and vision loss. The retinal cells most commonly affected are the photoreceptors, which include rods and cones, which detect light and color. Other retinal cells, such as bipolar cells and ganglion cells, can also be targets of these autoantibodies.
Recognizing the Symptoms
Individuals with autoimmune retinopathy experience visual symptoms that can progressively worsen. A gradual loss of vision is a common complaint, which may begin subtly and then become more pronounced over time. This vision loss can sometimes start with difficulty seeing in low light conditions or at night, known as nyctalopia or night blindness.
Patients also report increased sensitivity to light, termed photophobia, or the perception of flickering or flashing lights, photopsias. Visual field defects, or blind spots, are observed, and these can vary in size and location. Patients may also have trouble adapting to changes in light intensity, such as moving from a brightly lit room to a dim one. While the condition affects both eyes, the severity of symptoms can be asymmetrical.
Diagnosing the Condition
Diagnosing autoimmune retinopathy involves specialized tests to assess retinal function and detect specific markers. A comprehensive eye exam is the first step, though the appearance of the retina can initially seem normal. Visual field testing is performed to identify blind spots or areas of reduced vision.
Electroretinography (ERG) measures the electrical activity of retinal cells in response to light stimuli. In AIR, ERG often shows reduced amplitudes in both rod and cone responses, indicating widespread retinal dysfunction. Optical coherence tomography (OCT) provides detailed cross-sectional images of the retina, allowing for the visualization of structural changes such as thinning of retinal layers or disruption of the photoreceptor inner/outer segment junction. While OCT can reveal retinal damage, changes may not be apparent in the early stages of the disease.
Blood tests detect specific autoantibodies that target retinal proteins. Common autoantibodies associated with AIR include anti-recoverin and anti-enolase antibodies. However, their presence alone is not sufficient for a definitive diagnosis, as they can sometimes be found in healthy individuals or those with other eye conditions. A diagnosis of autoimmune retinopathy is generally made by combining clinical symptoms, ERG findings, OCT results, and the detection of these specific autoantibodies.
Treatment Approaches
The primary goals of treatment for autoimmune retinopathy are to suppress the immune system, reduce inflammation, and prevent further vision loss. Treatment strategies are individualized, depending on the type of autoimmune retinopathy and the severity of the patient’s condition. Immunosuppression is a mainstay of therapy.
Corticosteroids, such as prednisone, are used as a first-line treatment and can be administered orally, intravenously, or through injections into the eye. These medications reduce inflammation and suppress the immune response. For patients who do not respond adequately to corticosteroids or experience significant side effects, other immunosuppressants may be prescribed. These can include medications like azathioprine or mycophenolate mofetil, which modulate the immune system.
Intravenous immunoglobulin (IVIG) is another treatment option, involving infusions of antibodies from healthy donors. IVIG can neutralize the harmful autoantibodies attacking the retina. Plasma exchange, also known as plasmapheresis, is a procedure where a machine removes the patient’s plasma, filters out harmful antibodies, and then returns the treated plasma and blood to the body. This can quickly reduce the level of autoantibodies in the bloodstream. Ongoing monitoring of visual acuity, visual fields, and retinal function through tests like ERG and OCT is important to assess treatment effectiveness and adjust therapy as needed.