Glaucoma

Question 1

What is the most frequent cause for glaucoma in cats

Answer 1

Glaucoma in cats most commonly occurs as a sequel to chronic intraocular inflammation

Question 2

What is the pathomechanism of glaucoma

Answer 2

Pathologically high intraocular pressure interferes with retinal and optic nerve function
- glaucoma is thus a neurodegenerative disease leading to optic nerve atrophy and visual impairement or blindness

Question 3

What are the dynamics of aqueous humor

Answer 3

Aqueous humor is produced by the nonpigmented epithelium of the ciliary body and secreted into the posterior chamber

Aqueous humor may then leave the eye via one of two main pathways:
- in the cat, the majority (>97%) of aqueous leaves the eye via the “conventional” drainage route (through the pectinate ligament and trabecular meshwork into the aqueous plexus and scleral venous circulation)
- the uveoscleral route or “unconventional” route accounts for about 3% of aqueous outflow in the cat

Question 4

What is the normal feline IOP

Answer 4

Normal feline IOP is generally 10-25 mm Hg
- average normal IOP for young cats: 20 +/- 5 mm Hg
- average normal IOP for cats > 7 years: 12.3 +/- 4 mm Hg

A difference of 5 mm Hg or more between the eyes is considered a risk factor for glaucoma

Question 5

How frequent is primary glaucoma in cats

Answer 5

In contrast to the dog, primary glaucoma is very uncommon in cats

Question 6

How is primary glaucoma diagnosed

Answer 6

Primary glaucoma is diagnosed when no other cause can be attributed to the pathological elevation of IOP

Breed predispositions have been described
- Burmese
- Domestic short- and long-haired cats
- Siamese

Congenital glaucoma may be unilateral or bilateral, and arises as a result in maldevelopment of the aqueous drainage outflow pathways