SARDs/IMR — Awareness Central

What is SARDs / IMR?

Sudden Acquired Retinal Degeneration Syndrome (SARDs) and Immune-Mediated Retinitis (IMR)  are both auto-immune diseases.  An auto-immune disease is a disease in which the body forms anti-bodies to attack its own cells.  In the case of SARDs/IMR, the body produces antibodies that attack its own retinal cells, ultimately causing the onset of sudden blindness.

• For SARDs, it is believed that retinal auto-antibodies are formed locally within the eye.
• For IMR, it is believed that the retinal auto-antibodies are formed elsewhere in the body, and ultimately, through circulation, reach the eyes.

Although SARDS and IMR can cause sudden blindness, studies have shown that it is also an indicator of potentially life-threatening systemic issues.  Therefore, even though your veterinary ophthalmologist may not be able to restore vision to your canine, it does not mean you should ignore its systemic health.

By better understanding SARDS and IMR, you may be better able to provide a healthy and long life for your canine companion, despite the loss of his vision.

What are precursor conditions prior to the onset of SARDS / IMR?

Canines that ultimately develop SARDs/IMR have a history of  some or all of the following behavioral and clinical symptoms:

• Reluctance to jump on/off platforms, such as beds and sofas, in dim light conditions.
• Reluctance to walk down the stairs in dim light conditions.
• Reluctance to chase a ball if it is closer than 10 feet, but will chase it if thrown further away.
• Abnormally dilated pupils for months, or years, before the “sudden” onset of blindness.
• Polyphagia (“excessive” eating), often causing weight gain.
• Polydypsia (“excessive” drinking)
• Polyuria (“excessive” urinating)
• Hypersalivation
• Tearing eyes
• Seasonal skin allergies
• Food allergies
• Vaccination allergies
• History of previous, or current, tumors (neoplasia), which is applicable to IMR, not SARDs.

According to Dr. Grozdanic’s research at Iowa State University (ISU), approximately 90% of SARDS & IMR patients have had some or all of the following auto-immune diseases:

• Seasonal skin allergy.
• Food allergy.
• Immune-mediated hemolytic anemia, immune-mediated thrombocytopenia.
• Post vaccine allergic reactions.
• History of previous or current tumor (neoplasia) — for IMR patients.

The following conditions are also present in 40-50% of the patients with SARDS:

• Polyphagia – excessive eating, which may lead to weight gain.
• Polydipsia (PD) – excessive drinking
• Polyuria (PU) – excessive urinating

Apparently, approximately 20% of IMR patients also have the above symptoms.

Also, the above symptoms may manifest months or years before the onset of noticeable visual deficiencies in your canine.

If your canine has any of the above conditions or symptoms, you should visit a veterinary ophthalmologist and get spectral pupil testing and a fundus evaluation.

How is SARDS / IMR diagnosed?

SARDS and IMR can be diagnosed by your veterinary ophthalmologist by performing a combination of these tests:

• Blue Light Pupil Light Reflex (PLR)
• Red Light Pupil Light Reflex (PLR)
• Eletroretinogram (ERG)
• Testing for presence of retinal auto-antibodies (specific to IMR).

Blue Light PLR

• Both SARDs and IMR canines will have a good Blue Light PLR response.  This means that when a blue light of a specific wave-length is shined into the eye of the canine, the canine’s pupil will constrict.
• If there is no response to blue light, the case is probably neither SARDS nor IMR.

Red Light PLR

• For SARDS patients, there will be no response to red light at all.  The pupils will remain dilated and will not constrict.
• For IMR patients, there will be some response to red light.  The response may not be good, but the pupil response will always be present.

Electroretinogram

• For SARDS patients, the ERG will be flat.
• For IMR patients, the ERG may or may not be flat.

Retinal Auto-antibodies Presence Test

Although, the results of the Red Light PLR can help provide a definitive difference between a SARDS and IMR diagnosis, there is a specialized test that can be run to detect the presence of retinal autoantibodies, which would indicate an IMR condition; however, this test is not commercially available and in its current state of testing, takes 4-6 weeks.

Due to the prolonged time required for the retinal auto-antibodies test, the PLR tests using blue and red lights are both an effective and time-efficient means of diagnosing SARDS or IMR.

What are the treatment options for SARDS / IMR?

There are currently two (2) forms of treatment for SARDS / IMR.

• For immediate treatment, a strong prescription combination of steroids and antibiotics (prednisone and doxycycline, for example) can help to suppress the auto-immune response, and to help stop the rapid deterioration of vision to preserve what vision your canine currently has.
• There is also an experimental treatment utilizing human immunoglobulins (IVIg) to potentially help restore or maintain additional sight capability.   The human immunoglobulins can be administered intravenously, or a localized intraocular treatment can be delivered directly into the eye via an injection.

What are the risks with IVIg treatment for SARDs/IMR?

As with any medical treatment, there are always risks.  Please thorougly review  Sudden Acquired Retinal Degeneration Syndrome (SARDs) and Immune Mediated Retinitis (IMR)  — approach to diagnostic and therapeutic modalities on the Documentation page.  At a high level, the following risks should be considered:

• IVIg treatment may cause a severe allergic reaction to the patient.
• Intra-ocular treatment involves using a syringe to inject Ig directly into the eye of the patient.  The inherent risks with this treatment should be obvious.
• There is no data to show what the long-term effect is to the patient.

IVIg treatment for SARDs was first successfully performed at Iowa State University (ISU) in April of 2007, and since then, there have been additional cases of successfully treated canines.

However, keep in mind that IVIg treatment is relatively new, so there is no data that shows the long term effects on canines that have received this treatment.

Now that you’ve read the SARDs/IMR Primer, please read this blog posting on How to Diagnose SARDs/IMR.

If you have any questions, please feel free to email us at info@sardsawareness.org.