Glaucoma: Time to look past the eyelids!
Glaucoma: Time to look past the eyelids!
by Marybeth Cline, DVM & Eileen Peers
Bloodhounds and Ophthalmologists: two words that are seldom put together. Brings to many minds the polar bipartisanship we see in our politicians! Many of us have had the experience of seeing the pain on an ophthalmologist’s face when they see a bloodhound. We have all been conditioned to be mindful of our lovely, loose eyelids; not too folded in, not folded out, and watch that pesky third eyelid too! Time to look past those eyelids!! Those of us that breed may do the occasional CERF test as recommended, provided we find a clinic at a show….and its cheap. How many of us actually know what a CERF test is looking for? It is a test for an inherited, degenerative disease of the retina that will cause progressive blindness. I contend that there is an inherited disease of bloodhound eyes just as sinister and far more common that is NOT being regularly screened for: Glaucoma.
We have all heard the term. It is a term that can immediately cause the sick feeling in the pit of the stomach…and it should. It is among one of the most common causes of acute blindness in dogs. Its causes can be many fold: some that are called primary (congenital or inherited) some are secondary to other causes or injuries. We will discuss both here, but for breeders, the one to worry about is primary glaucoma. Long thought to be mostly a disease of smaller breed dogs or arctic breeds, it is becoming more recognized in other breeds of dogs, including our beautiful bloodhounds.
The “plumbing” of the eye, if you will, is a complex system that produces and circulates the fluids of the eye, and then drains them to maintain a safe and constant pressure within the eye itself. The aqueous humor (fluid in the eye) is produced in the rear chamber of the eye by cells called the nonpigmented ciliary epithelium. The aqueous fluid produced, circulates to the front chamber of the eye (the one you can see if you look at your dog’s eyes) where it drains at the iridiocorneal angle (the place where the dog’s cornea and iris meet along the edge of the eye. If too much fluid is produced, or the drains that allow the fluid to escape are compromised, the pressure of that fluid in the eye immediately starts to increase, called glaucoma.
Primary vs Secondary
Primary Glaucoma is most often a bilateral, breed related disease. It is most often characterized by the eye having no apparent abnormalities on a routine eye exam. While most dogs will present at first with only one eye affected, over 50% of those dogs will go on to develop disease in the other eye. It has been shown that many breeds are considered predisposed including beagles, and bassets to name a few. Additionally, female dogs may be at increased risk, and onset of signs will be in dogs usually aged 5-10 years. (1) In all types of primary glaucomas, fluid production is normal, but the drainage angles are malformed, decreasing aqueous fluid outflow and increasing intraocular pressure.
Secondary Glaucoma is just what it suggests; it is secondary to some other disease process or injury. There are a number of systemic diseases that can lead to glaucoma as a result. Systemic infections (bacterial or fungal) or autoimmune diseases, can have glaucoma as merely a symptom of a much bigger disease process. Traumatic injuries to the eye, tumors of the eye, or infections in the eye, can also impact either production of fluid or create clogged or swollen drainage passages, leading to an increase in eye pressures, again secondary to another issue.
Clinical Signs and Diagnosis
The clinical signs of glaucoma are fast moving. As a dog owner, you will see a very rapid onset of a red, painful, tearing eye. The dog will probably either be squinting, or have the third eyelid prominent. Any of these signs is a call for a trip to the veterinarian. Do not wait. Time is of the essence. ALL RED EYES SHOULD BE PRESSURE CHECKED! All veterinarians are taught this mantra when studying eye health issues in veterinary school, and dog owners should know it too! Normal pressure in eyes is below 25 mm/Hg. Any increase in pressure beyond this will cause compression and permanent damage to the optic nerve, rendering the dog blind in a matter of hours to days if not corrected. This increase in pressure is always painful to the dog. In more extreme cases, the cornea of the eye will appear a hazy light blue color, or the eyeball itself may appear enlarged, compared to the normal eye. Your regular veterinarian will be able to check the pressure in the eyes in minutes with a simple test using an instrument called a tonometer. A drop or two of topical anesthetic, and a few taps with the tonometer (an instrument that looks like a magic marker with a rubber tip) and a digital reading will be known. Based on that reading, if pressures are elevated, there are a number of treatment options ranging from eye drops, to oral medications, or even a trip to the ophthalmologist for consult and surgery in difficult cases, but it is treatable and controllable.
But the concern for breeders is early detection on breeding animals. There is a test for that! Time to “reach across the aisle” and make friends with the ophthalmologist! The test is called gonioscopy. In this test, the eye specialist uses a specialized instrument to examine those drainage angles in the eye we discussed earlier. If those drainage areas are malformed or smaller than normal, the aqueous fluid cannot drain properly, thus certainly leading to a backup of fluid and an increase in eye pressure. With this test, it can be determined if a dog is at risk for development of the disease, and a potential carrier of the problem.
GOING FORWARD WITH GONIOSCOPY
More and more breed clubs and health professionals involved with dog breeding are suggesting adding gonioscopy to the CERF test for eye health testing of breeding stock, including your ABC Health Committee. It is more of an expense, as it is an additional test, but the implications for future eye health and clearance of breeding stock cannot be ignored. It IS something we see in our breed, and we DO need to be on the lookout for it. If you can get the advanced notice of risk on a dog, you can take steps to save his sight, and have an additional tool in your arsenal to evaluate any potential breeding stock for this devastating disease.
A BREEDER TESTIMONIAL
“Larla is such a poor girl and so brave. Maybe she is the one saving the breed from this new problem.”
These are the words of the co-owner of a Continental Bloodhound who has lost her eyesight in both eyes from the very painful condition of Glaucoma.
We need to get the word out to all Bloodhound Breeders all over the World. None of us can want to breed a bloodhound who has suffered so much.
The eye check needed BEFORE breeding for the bitch and the dog is really simple and inexpensive. There are two tests an intraocular eye pressure test and a Gonioscopy test. The response from worldwide breeders so far has been almost zero.
Before you lose interest at yet another health check BE AWARE THAT IT MUST ALREADY BE widespread in the breed otherwise it would not have been shown up in Larla. Larla is close to a outcross. Her pedigree shows many different well known lines – European ( including French, Belgian, and Dutch), American, and British. The only way we find out is checking every single breeding dog.
The problem is well known already in many other breeds, including Basset Hounds. It is a recessive gene which is causing a change in the eye which may - or may not - develop into glaucoma, a VERY PAINFUL problem which will blind the dog within hours. In an ideal world would check for it (not a difficult test, can be done in puppies already) and choose our breeding according to the findings . It is recommended is to breed a clear only to a clear. This would, therefore, master the problem within a few generations.
The American co-breeder of the sire was very honest, and should be admired and thanked for talking about it. She did not cover up or hesitate. If only all breeders were this brave. She had unfortunately seen a few bloodhounds with glaucoma from different breedings. The breeder and both co-owners of Bloodhound Larla stood up at once, again no hesitation or cover up. The welfare of the Bloodhound is paramount.
So let’s just test all dogs and bitches from now on before they are bred from. It costs so little and saves such pain. We owe it to Larla, let her suffering at least save other Bloodhounds.
And please Breeders, don’t sweep it under the carpet. If you find you have bred it, stand up and tell your breed club – wherever you are in the world. Let’s start to collect data. Let’s try to stop it before it becomes common in our breed. Right now the discovery is still new. It is possible that we can stop it with not breeding clear to clear. The more data we collect the more we will know.
If you truly care about the future of the Bloodhound, this is one important, but easy step to take.
Eileen Peers - Cilgwri Bloodhounds
(1) Kural, E; Lindley, D; Krohne, S: Canine Glaucoma: Clinical Signs and Symptoms; from Ophthalmology in Small Animal Practice. 1996