Retinal Disease Retinal Degeneration can be slow and worsens over time, as in Progressive Retinal Atrophy (PRA), which is similar to macular generation in humans. The retina is the portion of the back of the eye that contains the rods and cones. Rods help detect motion and black and white differences and cones help us distinguish colors. While our pets have different vision perception than we as humans do, they do have the same anatomical structure of the retina.

Another form of retinal loss is Sudden Acquired Retinal Degeneration Syndrome (SARDS), unlike the gradual blindness that occurs in PRA pets, SARDS pets become suddenly blind with no forewarning. The cause of SARDS is unknown, but is likely autoimmune.

Symptoms

Symptoms can include reluctance to use stairs, clumsiness (bumping into things), dilated pupils (or pupils that react strangely), night blindness (that progressively worsens), and sudden blindness.

Breed Specific

The cause of PRA is largely genetic and is mostly seen in the Briard, Cocker Spaniel, Collie, Irish Setter, Labrador Retriever, Mastiff, Miniature Poodle, Samoyed and Siberian Huskie.

SARDS is seen in 70% of female dogs and normally strikes in middle age. Most commonly seen in Dachshunds, Miniature Schnauzers and mixed breeds; whereas, mixed breeds are at a higher than average risk.

Diagnosis

Examination of the eyes of affected pets with PRA can show increased reflection of light from the retina, as well as loss of the normal blood vessel pattern and number of blood vessels of the retina. Many veterinarians can make this diagnosis without the need for a veterinary ophthalmologist. Veterinary ophthalmologists, when available, can better help determine the severity and outcome of patients suspected of having PRA.

SARDS pets become suddenly blind, which is different from the gradual blindness occurring in PRA pets. Once SARDS is suspected, it is best to perform an Electro Retina Gram (ERG). An ERG determines the amount of electrical neural output the retina is sending to the brain. This test is helpful in determining if any vision is left in the pet.

Common Treatment Protocol

While there are screening tools that can detect the disease before any physical signs are noticed, there was no known hope for the blind pet (or for the pet going blind with PRA or SARDS), prior to stem cell therapy. Due to ongoing research into similar diseases in humans, there is now hope for our pets with stem cell therapy.

Stem Cell Treatment

The eye has special protections not afforded to other organs, however, that makes it more difficult to treat with stem cells. There is a blood retinal barrier that prevents substances (and stem cells) from entering the eyes from the blood. Therefore, IV injections of stem cells are not as effective as we would like. Because SARDS may be an immune mediated disease, IV cells may ameliorate the progression of the immune attack, but they will not be able to help the retina heal or regenerate.

Through research in humans and in some clinical trials, injections directly into the vitreous of the eye have been a good method of delivery of medications to the retina. This method has also worked well with stem cells, but there is an unacceptable level of adverse reactions and scar tissue that can form in some cases, resulting in permanent blindness. Recently, a method of injection into the tissues capsule (choroid) of the eye has been shown as a safe, effective delivery method for stem cell application.

Safari is working to develop these delivery methods so pets with PRA and SARDS can benefit from the most advanced and safe methods for treating these terrible diseases. Currently, at Safari, SARDS is treated as an immune system disease with IV injections of stem cells injected into the back of the eye.

The sooner stem cells are given in the course of the disease, the better the response to treatment is. If we wait too long, even stem cells cannot restore vision.

Further Reading

PDF ICON Stem Cell Treatment in Retinal Diseases: Recent Developments
The Suprachoroidal Space: From Potential Space to a Space with Potential (Suprachoridal Injections)

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