Quote from Canine Glaucoma Editor on April 24, 2023, 1:09 pm

While glaucoma is always defined as high interocular pressure, the causes are varied and can impact both the progression of the disease and its treatment. It is essential that your veterinary ophthalmologist perform a thorough exam to establish the type of glaucoma and course of treatment.

Primary Glaucoma

Hereditary or "Primary" glaucomas like "Primary Open Angle Glaucoma" (POAG) and "Primary Closed Angle Glaucoma" (PCAG) are inherited from the dog's parents, both of which have to carry the mutation in order for it to pass to the offspring. POAG tends to be a slower progression while PCAG is often acute and presents as an emergency situation. Neither of these primary glaucomas are reversible and almost always lead to total blindness. 

Secondary Glaucoma

Secondary glaucoma is caused by an underlying condition and sometimes treatment of the condition can halt the progress of the increasing interocular pressure. Some common causes of secondary canine glaucoma include:

1. Inflammation: Inflammation of the eye due to infection or injury can cause the drainage channels in the eye to become blocked, leading to an increase in intraocular pressure and subsequent glaucoma.

2. Lens luxation: This is a condition where the lens of the eye becomes displaced from its normal position, causing obstruction of the drainage channels and leading to secondary glaucoma.

3. Tumors: Tumors in the eye or surrounding tissues can interfere with the normal flow of fluids in the eye and cause secondary glaucoma.

4. Trauma: Any injury to the eye can damage the drainage channels and lead to secondary glaucoma.

5. Uveitis: Uveitis is inflammation of the uvea, the middle layer of the eye, and can cause secondary glaucoma.

6. Cataracts: If left untreated, cataracts can cause secondary glaucoma due to increased pressure on the drainage channels.

7. Inherited disorders: Some dog breeds, such as the Basset Hound, have a higher risk of developing secondary glaucoma due to inherited disorders affecting the drainage channels.

It is important to note that secondary glaucoma is often a complication of another underlying disease, and treating the underlying cause is essential for successful management of the condition.