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Canine Primary Glaucoma - Do you feel the pressure?

Canine primary glaucoma is one of the most difficult and frustrating eye diseases you will encounter.  In this newsletter we will discuss tips on diagnosis, emergency treatment and vision preserving surgeries at Melbourne EyeVet.

Diagnosis

Breeds commonly seen in Australia with primary glaucoma include Maltese, Golden Retriever, Cocker Spaniel, Hungarian Vizsla, Samoyed and many others.

Clinical Signs

  • Corneal oedema (diffusely blue eye)
  • Deep perilimbal hyperaemia
  • Mid-dilated, non-responsive pupil
  • Vision loss
  • Pain

Examination
Check the vision in any red or blue eye that you see. This can sometimes be the first hint that there is a serious problem. Many early glaucoma cases present with a vague red eye that looks fairly innocuous. Perform menace responses and if absent suspect more serious disease.

Tonometry

Measuring the eye pressure is difficult in an anxious and stressed dog.  

  1. First take off all collars and harness and let the dog relax. 
  2. It is vital not to place any pressure on the neck or the globe when you are measuring the eye pressure. 
  3. If you are using a Tonopen apply local anaesthetic. None is required if you are using a TonoVet.
  4. Gently open the eyelids, taking care not to put pressure on the globe, and measure the pressure.

Follow the instructions carefully from the manual of your tonometer.  It is important to keep the instruments clean.

How to correctly use and take the eye pressure using a tonovet

Emergency Treatment for Primary glaucoma

  1. Phone Melbourne EyeVet.  An initial consultation ($190 during normal hours at the main clinic) will allow accurate diagnosis and determine whether the glaucoma is primary or secondary.
  2. When referral is not an option consider Xalatan (latanoprost) as long as you are certain there is not an anterior lens luxation. In some cases, latanoprost alone can reduce pressure from above 50 mmHg down to 10 mmHg within 60 minutes.
  3. If the cornea is healthy, topical NSAID or Prednefrin Forte should be used to control any underlying uveitis.
  4. Systemic NSAID or oral steroids should be consider to control inflammation.
  5. Systemic opioids can also be used for pain management.

What Next?

Even with continued medical therapy, the pressure will eventually rise.  Early referral is important in order to manage the glaucomatous eye (even if they don’t want surgery) and determine if the remaining eye is likely to develop glaucoma.

Vision Saving Surgery

There are two main options for vision saving surgery.  The first is cyclophotocoagulation where a laser is used to destroy the cells that produce the aqueous (the ciliary body).  The second option is to place a glaucoma shunt over the globe and insert a clear silicon tube into the eye.  This surgery provides the patient with a new drainage pathway and causes less inflammation.  Both procedures will require long term medication and early referral will give the best outcome. 

Glaucoma shunt
The approximate position where the glaucoma shunt will sit under the muscles around the globe
In this image you can see the shunt clearly
This glaucoma patient is doing well post operatively with a stable pressure and useful vision.
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Melbourne Eye Vet · 9-11 Miles St · Mulgrave · Melbourne, Vic 3170 · Australia

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