Hi, I’m Bessie. My silly humans thought I looked like a cow, since I am a harlequin Great Dane—hence the name. This morning when I woke up on my favorite couch, my eye really hurt, and things were looking a little fuzzy. My mom was worried about me, so she took me to Veterinary Vision Center, where they said that I have something called claw-coma. I don’t know why they are talking about claws since my eye was hurting, but they gave me some medicine, and now my eye is feeling great. I really liked Dr. Pierce, especially since he didn’t mind when I accidentally left a big string of drool on his leg, or almost knocked him over when I was leaning in for some more petting. My mom says we will have to keep visiting my friends at Veterinary Vision Center, so they can help me with my claw-coma. That is fine by me.

Glaucoma in pets

What Bessie calls claw-coma is really glaucoma, a condition where aqueous humor, the fluid in the front portion of the eye, builds up and causes increased intraocular (i.e., inside the eye) pressure. In a normal eye, the aqueous humor is produced by the ciliary body, and circulates in the eye’s front chamber, before exiting through the iridocorneal angle, a drain-like structure at the base of the iris (i.e., the colored portion of the eye). The delicate balance between aqueous humor production and drainage allows the eye to maintain normal pressures. However, if the aqueous humor drainage is slowed, then more fluid is produced than removed, leading to increased eye pressure.

Glaucoma types in pets

Glaucoma is classified as primary or secondary, depending on how it arises.

  • Primary — Primary glaucoma, which is due to a hereditary defect in the iridocorneal angle, is more commonly seen in cocker spaniels, basset hounds, beagles, Norwegian elkhounds, Great Danes, Siberian huskies, Jack Russell terriers, Samoyeds, chow chows, Shar Peis, and Siamese cats. Primary glaucoma usually affects both eyes at some point, but once diagnosed in one eye, steps can be taken to slow the progression in the other eye.
  • Secondary — Secondary glaucoma usually occurs in one eye because of anterior lens luxation (i.e., the fibers holding the lens in place break, and the lens falls into the front of the eye), uveitis (i.e., inflammation inside the eye), a mass in the eye, cataracts, or a traumatic injury.

Glaucoma signs in pets

Dogs in early stage glaucoma exhibit subtle changes, such as slight pupil enlargement, mild redness, or small increases in eye size that may go unnoticed. Glaucoma is more commonly diagnosed when pets start to show obvious clinical signs, such as:

  • Redness of the white portion of the eye
  • Blue, cloudy cornea (i.e., the typically clear outer portion of eye)
  • Excessive tearing
  • Enlarged or firm eye
  • Pain around the eye, or excessive blinking and squinting

In retrospect, Bessie’s owners had noticed that her eye sometimes looked a bit red, but chalked it up to allergies, until she woke up this morning with an extremely red and painful eye.

Glaucoma diagnosis in pets

As part of a complete ophthalmic exam, the Veterinary Vision Center team uses an instrument called a tonopen to non-invasively measure the pressure in Bessie’s eyes, and notes that her right eye pressure is significantly higher than normal. Dr. Pierce also evaluates the iridocorneal angle of Bessie’s eyes using gonioscopy, to further distinguish between primary and secondary glaucoma, and then, based on the exam findings and her breed, diagnoses her with primary glaucoma. If Bessie’s owner decides to adopt more Great Danes or other predisposed breeds, they should periodically have their eye pressures checked to ensure that any primary glaucoma is caught early.

Glaucoma treatment in pets

 Since glaucoma cannot be cured, Bessie will require lifelong management to keep her comfortable and visual for as long as possible. Two treatment options are possible:

  • Medical management — Our team may prescribe medications designed to decrease aqueous humor production, promote aqueous humor drainage, and control pain.
  • Surgical management — If Bessie is still visual, but medical management is no longer sufficiently controlling her eye pressures, Dr. Pierce can use a laser to kill some of the aqueous humor-producing cells, and/or insert a shunt to drain aqueous humor from the eye. If her eye becomes blind and painful, he may recommend removing the entire eye, or replacing the eye’s inner contents with a prosthesis, to provide pain relief.

When untreated, or incorrectly treated, glaucoma causes pain, retinal damage, and eventual blindness. If your pet is diagnosed with glaucoma, or is exhibiting eye abnormalities, promptly make an appointment with Veterinary Vision Center, as Bessie’s owner did, to ensure that your furry friend receives expert care from Dr. Pierce, our board-certified veterinary ophthalmologist.