Under Pressure: Part 1 Diagnosis of Glaucoma
By: Ellie BatesBailey, a 12 year old, male neutered Cocker Spaniel presented following a week’s history of a painful left eye.
Bailey’s right eye was normal and visual on ophthalmic examination. The left eye had a fixed and dilated pupil and was non-visual. There was also a marked corneal oedema and corneal vascularisation present round the limbus. The lens also appeared to be subluxated, which obscured the view of the retina. The IOP was 47mmHg.
In Bailey’s case, his owners opted for enucleation and histopathology to establish whether the cause of his glaucoma was primary or secondary and therefore whether his right eye could be affected. The histopathology report revealed the presence of benign diffuse uveal melanocytoma and secondary glaucoma, enucleation is curative. Bailey has made a full recovery from his procedure and his owners are really happy with how he has adapted to being a one-eyed dog.
Glaucoma cases can be tricky to work up and treat successfully at both first opinion and referral level.
The main questions to ask yourself when you first see these cases:
- Is it primary or secondary glaucoma?
- Is it acute or chronic?
- Is the patient blind?
- Does your patient have any concurrent disease?
Primary and secondary glaucoma can be determined by using a technique called gonioscopy to examine the drainage angle in the normal eye.
It is important to establish whether a case is primary or secondary as primary glaucoma is normally bilateral.
Remember some breeds are predisposed to primary glaucoma (see BVA Eye Scheme for more information)
Causes of secondary glaucoma include:
- Lens luxation
- Uveitis (the most common cause in cats)
- Intraocular neoplasia
- Intraocular haemorrhage
- Previous intraocular surgery e.g. cataract surgery
Acute or chronic cases can be determined by clinical signs.
In general, cases that have vision loss have a poorer prognosis because the damage to the optic nerve/ retina by the increased intraocular pressure is often irreversible and therefore it may be worth discussing enucleation at an earlier stage with the client. Staging a glaucoma can also help gauge the urgency of a referral but if you’re ever in doubt, urgent referral of glaucoma cases is often best.
