Veterinary ophthalmology

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This little Jack Russell terrier is polydipsic and polyuric and losing weight into the bargain. You look into his eyes for no particular reason (apart from your fascination with ophthalmology of course!) and this is what you see. What is the connection with his systemic signs?

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These apparent bubbles are vacuoles that are the earliest sign of diabetic cataract. All (or at least most!) of the books say that the classic diabetic cataract is one that suddenly presents as a mature white cataract like this one below.

But that’s, to my mind at least, just because diabetic dogs don’t get shown to an ophthalmologist until they are suddenly blind. In fact the vast majority of diabetics have vacuoles where water influx into individual lens fibres has occured way before they suddenly progress to being fully opaque. Now the question is what can be done to stop them progressing. If we could inhibit the aldose reductase enzyme converting the glucose to sorbitol which sucks in the water, no diabetic dog need be blind.  A topical preparation shown to have this effect is not available currently though has been reported (Kador PF, Webb TR, Bras D, Ketring K, Wyman M. Topical Kinostat ameliorates the clinical development and progression of dogs with diabetes mellitus. Vet Ophthalmol. 2010;13:363-8) and we have good evidence for similar results with an oral preparation, Ocuglo, but more of that when our study is complete!

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What eye problem is this wonderful ram likely to be suffering from, is he likely to pass it to his offspring and how would you treat him?

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This is a four horned Hebridean ram and these
animals have unusual colobomas in their upper eyelids, as can be seen here.

The coloboma, or absence of tissue, in the middle of the upper eyelid can lead to trichiasis, hair abrading the cornea, and pigmentation as above or frank ulceration as in two of this ram’s offspring, as shown below.

Surgery to close the defect may be required when the ocular surface pathology is this severe. The abnormality is closely associated with the four-horned-ness of these sheep, though the exact heritability is currently under investigation .

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Here is an image taken of focal lesions on the retina of an Eagle owl. They seem to have no effect on the bird’s vision but what are they and should we be concerned? Oh and what is the black slug lurking at the bottom of the picture?!

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The black slug is the pecten, a pleated sheet of the choroid which protrudes into the fluid posterior vitreous to provide nutrition and oxygen to the retina. But I’m really not sure about the focal dots on the retina. Here is another view.

Chris Murphy published a similar picture in his Raptor Ophthalmology paper in the Compendium of Continuing Education back in 1987 and I seem to remember said they occured after light damage but please forgive me if I’ve remembered that wrong Chris. What do you think they are?

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A favourite ex-student of mine called me from South Africa yesterday about a horse with a problem eye – or should that be an eye problem?!

 What is likely to be going on here, what ancilliary tests would be useful and what  treatment should Dilly give?

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 This ground glass or cake frosting appearance spells fungal keratitis and the prognoais is not that good in my view. Diagnosis can be confirmed by cytology showing fungal hyphae as below and fungal culture and sensitivity is called for.

Tonometry would show a reduced intraocular pressure because of a secondary uveitis. Dennis Brooks and colleagues in Florida would probably suggest a full thickness keratoplasty, but a debridement and treatment with an antifungal such as itraconazole or natamicin might suffice.

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 This German Shepherd Dog has just been brought in to a rehoming shelter and I’m called in to say what new owners should be told about the appearance of the cornea. The dog seems visual and comfortable at present but is there a potential problem here?

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 Given the breed of the animal, it is highly likely that this is quiescent case of chronic superficial keratitis or pannus as we used to call it. We are more used to seeing the condition appearing like this

 as a slightly raised neovascular lesion, but my guess is that the dog in question has been treated for the condition previously and that now it is wintertime the only lesions left are some focal areas of stromal pigment and a few blood vessels. The worry is that once the summer comes increased UV irradiation will set the autoimmune inflammatory processes off again and continual treatment with topical steroid or cyclosporine will be required. The best thing to do would be to put the dog on a low dose of prophylactic topical anti-inflammatory to ensure that the disease does not recur with avengance!

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 This 2 year old Springer spaniel has gone blind suddenly in this red painful eye. What is the lilely diagnosis and what is the necessary emergency treatment?

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Note the hazy cornea and the moderately dilated pupil. A red painful eye could be uveitis or glaucoma but even if you haven’t a tonometer to measure the intraocular pressure, the dilated pupil tells you its glaucoma rather than uveitis. The intraocular pressure actually was 56mmHg.

In the old days we would have used intravenous mannitol to reduce the pressure, but these days the topical prostaglandin analogue Xalatan has a wonderful effect, opening new drainage channels in the choroid and reducing the pressure rapidly. One drop lowered the intraocular pressure to 16mmHg within fifteen minutes, with a concurrent miosis of the pupil too.

 The nice thing is that the owners can monitor the response to treatment easily without recourse to a tonometer. A small pupil indicates an acceptable intraocular pressure while a mydriastic pupil shows that another drop of Xalatan is needed. We do have to worry that the other eye may develop the condition too, so a drop of Xalatan before bedtime will push back any such an event by a long time.

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 This horse belongs to the daughter of a non-veterinary colleague of mine. The lesion started several years ago and was first diagnosed as a reaction to a fly bite, but it’s clearly something much worse than that. It has already had several treatments to no avail at different veterinary centres. What does it have and what do you think I should do with it now?

I call it a  nightmare neoplasm as my youngest son said he would have nightmares having seen it earlier today. Can you give me a good night’s sleep with a sure-fire therapeutic strategy?! 

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 Here it is close up and even more horrible!

 This is a particularly nasty sarcoid. BCG injections, iridium wires and surgical debulking at other referral centres have only served to make it grow more aggressively according to the horse’s poor owner who is at her wits’ end. I think my solution is going to be a radical excision and exenteration with a mesh skin graft over the periocular area. But I would be really interested to know if you have any better ideas!

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  This cat looks very wide eyed doesn’t it? Wide pupilled one should say, if such a word exists! The cat can see but has no pupillary light reflex at all. It is somewhat constipated too, though sometimes rather the opposite (enough said!) and regugitates as well. What is your diagnosis and how might you confirm it?.

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 The cat has feline dysautonomia or what we used to call Key Gaskell syndrome. I say ‘used to’ as I haven’t seen a case since 1989 just after I qualified. Using the parasympathomimetic pilocarpine caused a very rapid and complete miosis, through the aceylcholine receptor upregulation at the motor end plate by Cannon’s denervation hypersensitivity. Here is the cat 5 minutes after applying pilocarpine to its right eye….

…and here it is after 10 minutes with a really highly miotic pupil…..

Quite what causes this condition is unclear, though as with grass sickness in horses there may be a link with Botulinum toxin. The cat has a megaoesophagus fitting in with the autonomic dysfunction. Have you seen one of these – there are one or two reported in the literature but maybe many more out there – do let me know if you’ve seen one!

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 What TLA  (three letter acronym!) might best describe this dog’s eye condition? And what additional TLA would give you the diagnosis for sure?!

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Well this eye has keratoconjunctivitis sicca (KCS) for which the diagnostic test is a Schirmer tear test (STT) as you can see here. The fact that the dog is a Jack Russell Terrier (JRT) and an annoyed one at that, in a muzzle to protect my fingers,  makes up the triad of TLAs!

Now being serious for a moment, this case illustrates how much ophthalmology is pattern recognition. While you might think that the discharge indicates infection or that the keratitis indicates a disease based in the cornea, the whole image just cries out ‘tear deficiency’ to me, so I was not surprised that the STT was zero. Topical cyclosporine has not had any effect, so while we source topical tacrolimus, a tear replacement such as a carbomer or hyaluronic acid, is the next best thing. 

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