Suspicious of glaucoma in a dog, but now what???
Ocular pain, corneal oedema, episcleral congestion, mydriasis, and vision loss are all possible signs of glaucoma, but accurate measurement of intraocular pressure (IOP) is essential to clinch the initial diagnosis.
There are a variety of different tonometers available from the old-fashioned Schiotz indentation tonometer to the newer TonoPen applanation tonometer and TonoVet rebound tonometer. All require minimal restraint around the head and neck for an accurate reading as neck compression and manual eyelid retraction can result in falsely high readings and a misdiagnosis, especially in wriggly brachycephalic breeds.
If glaucoma appears to be present, the diagnosis needs to be further refined into primary (no other ocular disease present) or secondary (another disease triggering) glaucoma, and the specific cause of the glaucoma identified – that’s where a specialist assessment is usually needed. Typically, we start with gonioscopy, a procedure used to assess the physical appearance of the entrance to the iridocorneal angle and pectinate ligament. Assessment define the nature of primary glaucoma and can identify abnormalities contributing to secondary glaucoma. With primary glaucoma, prophylactic management of the second eye is critical and has been shown to delay the onset of elevated pressure and maintain vision for longer. Other diagnostics including ocular imaging can also help determine the cause of secondary glaucoma.
There are multiple management and medical strategies for glaucoma, and of course any primary condition needs treating in the case of secondary glaucoma. Antiglaucoma medications should be carefully considered and one strategy does not fit all cases!!
- Carbonic anhydrase inhibitors (dorzolamide hydrochloride 2%, brinzolamide 1%)
• Reduce aqueous humour production
• Safe for any type of glaucoma
- Prostaglandin analogues (latanoprost 0.005%, travaprost 0.004%)
• Increase uveoscleral outflow of aqueous humour and may also increase corneoscleral outflow
• This medication will cause miosis and conjunctival hyperaemia
• CONTRAINDICATED with lens luxation, pupillary block glaucoma and uveitis
-Dr Zoe Anastassiadis BSc DVM MANZCVS