Dear friends and colleagues, after many years of my trusty old website acting as an opportunity for sharing some of the cases I see and the work that I am publishing, the creaks and groans of the old site are becoming just a bit too obvious.
So with the help of my great friend Richard Frank, who designed the first site back in 2004, I am starting a blog of sorts to continue a site that I hope will be of interest to those of you just starting out in veterinary medicine and thus needing to see examples of eye diseases, and also those of you with experience in the field, who I hope can help me with some of these less standard cases.
Here is one to start you off.
A five year old guinea pig with this weird deposit around the limbus in both eyes. What is happening here and does it matter to the animal?
This is heterotopic bone formation, occurring because of vitamin C entering the eye with the aqueous humour at the ciliary body, which stimulates this abnormal bone formation. Some consider that this leads to glaucoma, though this eye had a subnormal intraocular pressure of 9mmHg.
The key paper on this condition is Dennis Brookâs report (Heterotopic bone formation in the ciliary body of an aged guinea pig. Laboratory Animal Science 1990;40:88-90) though the prevalence of the condition is low in the pet population, with a figure of only eight animals having the condition in the thousand normal cavies we examined for our recent report (Williams D, Sullivan A. Ocular disease in the guinea pig (Cavia porcellus): a survey of 1000 animals.Vet Ophthalmol. 2010;13 Suppl:54-62) and these generally having a much less severe manifestation of the disease, as seen below.
Note also that the guinea pig above has a white cataract dorsally, this time a condition seen very commonly in our survey.
Do these ocular changes mater to the guinea pig? Most seem to cope very well with visual disturbance and pain does not seem evident, although of course these are a prey species, which opens a whole can of worms in understanding how they might show distress or pain!
thus looks like a condition called corneal pannus
No I’m afraid not – pannus (i.e. in the German Shepherd Dog, is a fleshy pink vascularised lesion slightly protruberant form the corneal surface while this is a white lesion within the peripheral cornea in the guinea pig characteristic of heterotopic bone formation. I’ll pop a pannus case on today if I have time so you can see the difference! Thanks for your comment though. David