Hello, everyone. My name is Ron Offrey. I'm a professor of veterinary phthalmology at the Hebrew University of Jerusalem, and I'm here today to talk to you about feline ophthalmology.

In fact, I just ended a two-day symposium in China online, of course, because one cannot enter China nowadays. Devoted to feline ophthalmology because it's really amazing to see how many diseases in the cat are different from, those in the dog. There is a long list of thalmic diseases that we treat totally differently in dogs and cats, which is really the subject of today's talk.

A cat is not A small dog, a dog is not a big cat. There are some diseases that you approach differently, you work up differently, you treat differently, or you don't see in one species or the other. So really what we'll do today is take a quick journey through the eyes, starting with the globe, and then from the front part of the eye, the eyelids and the eyelashes to the Taiwa and cornea and iris all the way to the retina in the back of the eye, just outlining what's different between dogs and cats.

Some of these topics have actually been covered in my previous webinars, or will be covered in upcoming webinar, and I'll refer you to those when they come up. So, starting things off with the globe, here are two animals with traumatic protosis, a dog and a cat, and if this was a live recording, I'd now ask you to take a poll question and vote on whether you think the dog or the cat has a better prognosis. And if you wish you can actually pause the recording for a minute or two to think about it, so pause the recording.

Welcome back. And I hope that after thinking about it, you have voted that the dog has a better prognosis. And that's because when you look at the cat, as we know, cats have very deep orbit with eyelids closing very Closely over the globe.

The globe is really protected by tight eyelids and a very deep orbit and therefore, in the case of a cat, it requires massive trauma to cause traumatic proptosis and you can see an indication for that here in this picture, there is obvious typhi. And there is probably a fracture in the mandibular synthesis, all indications that it required massive trauma to cause traumatictosis in this scan. So a massive trauma obviously carries a worse prognosis as compared to the dog where most often we see traumatic proptosis in In brackycephalic breeds like the Pekinese or the pug or the French bulldog that you're seeing, and in these breeds, you know, with the shallow orbit and the eyelids that barely cover the globe, the eye is really hanging out.

All the dog has to do is sneeze and the globe comes flying out of the orbit, so really minimal trauma to cause. Protosis and therefore the prognosis is much better and we can see this indicated in this study here looking at 18 cats with traumatic proptosis, you can see that 2/3 of them had to be nucleated because of of severe trauma to the eye. Another 4 had to be euthanized because of severe trauma to the head or to the body.

The globe was salvaged cosmetically just in 2 of the 18 cases. None of the cats were visual. So Really when the owner of a pet comes to me with traumatic protosis, I, and asks me, doctor, can you save the eye?

I really divide that question into two different questions. Can you save the eye that, so that it would be a visual eye? Or can you save the eye cosmetically so that even if it's blind, at least we can salvage the globe cosmetically and the cat will have two eyes cause aesthetically it's very important to owners.

So in cats presenting with traumatic proptosis, I'm afraid that the answer to both questions is no, chances for vision are extremely low and in fact even chances. For cosmetically salvaging the globe are quite poor. This is compared to dogs and the same study looked at 66 dogs.

So once again, 18 had to be nucleated and 4 had to be euthanized, but that's a total of 22 out of 66, so one third of the cases ended up being nucleated or euthanized, but 2/3, you had. A cosmetic salvage of a blind globe or vision was maintained. So my answer to the owner of a dog presenting with traumatic proptosis would be totally different.

Yes, there is a good chance I can maintain vision in this, dog, and even if I can't preserve vision, there is a good chance that we can salvage the globe. So really a significant difference between dogs and cats with traumatic proptosis. Most dogs that, present with traumatic proptosis, will have a globe functional or not functional, but they will have a globe, sometimes with a corneal ulcer or or lateral strabismus, but the globe is salvageable as opposed to cats, where in most cases they would have to be nucleated.

You may have noticed that this was a study from 1995, meaning that more than 25 years went by since then, but we recently duplicated, replicated these results in a study we just published with my resident Oren Peer shown here working in these COVID days and I take the opportunity to wish you and yours best of health. Still with the globe and the orbit, just like in dogs, we do get retrovular diseases in cats and just like in dogs, we are talking about retrovulbar abscess and retropulbar tumours. However, in general, these diseases are much less frequent than in dogs.

Here is a study looking at retrobubar. Tumours in dogs and cats and just compare the numbers you see that the investigators were able to collect 79 dogs but only 13 cats, so 1/6 the Incidents in tumours and while I don't have a similar study to show you in retro our abscesses, the proportions would be the same. Another thing to learn from this table is that Meningioma, which is a primary tumour of the optic nerve, is quite common in dogs.

In fact, it's the second most common retrovulbar tumour in dogs. As you can see, we don't see meningioma in cats. In fact, all of the retrovulbar tumours are secondary tumours.

They are metastasis. They are not. Binary tumours of the optic nerve.

So yes, we do see retrob disease in cats much less often than we do in dogs, but when we do see it, then the resulting exopthalmus is much more dramatic because of the restricted orbit that I mentioned earlier. Moving on from the globe to eyelids and eyelashes, you know that in dogs, entropion, ectropion, and dysthychia are very common disorders, mainly because they are inherited in so many canine breeds. All of these disorders are very rare in cats and we don't see them very often.

However, one eyelid disease that we do see in cats that we never see in dogs, is Ilid agenesis or coloboma. It's a disease that we see not just in the domestic cat, we see it in many wildlife feline species and as the name coloboma or agenesis implies, the cat is missing a piece of the eyelid. And as you can see in this picture.

And as it says in the text, we are invariably talking about the upper eyelid and the lateral part of the upper eyelid. So you can see here that the medial part is present and then all of this is missing. Same in this cat, we have.

1 centimetre of middle upper eyelid present and then the rest of it is missing. And obviously if the eye, a piece of the eyelid is missing, then facial hair can come in contact with the cornea cause one of the functions of our eyelids is to get facial hair away from the eye. So you can see facial hair rubbing on the cornea, causing keratitis.

You can see the vascularization here and here. So there would be pain involved obviously with hairs rubbing, there's keratitis, there is also exposure keraitis cause the blinking function of the eyelids is disrupted. Obviously, this cat cannot blink as well as a normal cat.

It's not spreading the tear film across the cornea and therefore you get exposure and possible ulceration. Obviously, this cat, would, these cats would require surgical treatment. There is no medical treatment for this condition and we have to come up with some sort of graft, to fill in the missing defect.

And if you go to textbooks. There are lots of methods showing you how to treat these cases. Some people take the flap from the lower lid and transpose it to the upper eyelid.

Here is a case where we are taking actually the commissure of the lip and transposing. And that's because the lip also reforms the lateral canthus. So since this cat was missing the lateral campus, we reformed it by taking one from the lip and we don't have to worry about reforming it and obviously the lip is very rich in .

It's a a line with a mucous membrane. The inner aspect of the lip is lined with mucous membrane, the outer part is lined with the skin, so it makes a very nice substitute for an eyelid. Just like in dogs, we see I tumours in cats.

We don't see them as often as in dogs, but they are much worse news in cats. In dogs, most eyelid tumours are benign. We're used to seeing adenoma, maybe adenocarcinoma, we see lots of papilloma.

These are mostly benign tumours that can be. Easily removed and pose no danger to the dog. Unfortunately, in cats, the most common eyelid tumour is squamous cell carcinoma.

And just like in other species such as cattle or horses, white cats are predisposed, probably because Because, the pigment serves, the pigment in the skin plays a protective role in protecting the eyelid from ultraviolet radiation. Ultraviolet radiation is what causes transformation of the normal tissue into neoplastic tissue. Squamous cell carcinoma would usually present as an ulcer on the eyelid, maybe with some crusting in or near the eyelid margin, so.

We're seeing here another white cat with what looks like an eyelid ulcer on the eyelid margin. However, this is a squamous cell carcinoma, but note how similar it looks to this case of viral dermatosis which also looks like an eyelid ulcer, which really tells you that every Every eyelid ulcer that you're seeing in a cat, especially white cats, must be sampled psychologically or histopathologically in order to rule out squamous cell carcinoma because these can really masquerade as simple ulcers and sometimes we see ulcers as small as 1 or 2 millimetres. We take a scrape and it's squamous cell carcinoma and we are darn happy that we took that scrape cause obviously, the sooner you catch it, the easier it is to remove it because whilst Squamous cell carcinoma rarely metastasizes, it is locally very, very aggressive and therefore we need to remove it with extremely wide margins, which is why you're better off if you diagnose it early.

Again, if you. Go to textbooks, you'll, you'll find a huge variety of techniques describing how to remove this with wide margins and filling in the defect. One method that I like to use is called the H plasty.

So here we have a squamous cell. Carcinoma, we are making a triangle, sorry, a rectangle around it to remove it. So here we remove the tumour, then we continue the vertical incisions down and you can see from this formula that this incision is 1.2 times the length of this incision and we removed two skin triangles, and now you can get a feeling for why it's called Hplasty.

So it looks like a letter H with the two triangles removed and then we free up the skin here, slide it to fill in the gap. Suture it, make sure you're doing a figure of 8 suture to get nice alignment of the eyelid margin, and this is what the final result would look like. So again, the cat that you saw earlier with this ulcer that turned out to be squamous cell carcinoma, and here is what it looks like after Hplasty with a nicely restored eyelid margin.

However, these tumours may definitely spread from the eyelid to involve the conjunctiva and the cornea, and when that happens, then obviously we need more radical excision and look here in this paper published actually by a surgeon from our school by what we mean. What I mean when I say radical excision, look at the amount of tissue that had to be removed, because of squamous cell carcinoma, and we definitely recommend that you combine it with some sort of adjunct therapy such as cryosurgery, hypothermia, photodynamic therapy, etc. Etc.

And I say that squamous cell carcinoma is a bad news cause while they rarely metastasize, still the survival rate is very poor, as you can see in This study, you can see 100%, those of you not familiar with this type of plot, 100% survival at day zero. After just 5 months, we are down to 33%, perhaps 30% survival. We are down to about 20% survival after 17 or 18 months.

So really 20%. Survival after a year and a half. That is very bad news.

And again, it's not because the tumour metastasizes, it's because of the radical excision that is needed to remove the tumour. If the tumour were to come back in this cat, there is very little you can do about it or maybe the owners are unwilling to go through another radical procedure again and they will decide to euthanize the cat. So here is the study from which the plot I showed you previously was taken, looking at I tumours in 43 cats.

You can see that squamous cell carcinoma is the most common tumour in cat and mast cell tumour not far behind and adenocarcinoma is unfortunately in a distant 4th place. So nasty tumours to look at in cases of feline eyelid tumours. Here is a tumour you may not be familiar with, sorry, here, you can see apocrine hydrocystoma mentioned here.

So that is what apocrine hydrocystoma looks like in case you haven't seen one. They're common in Persian cats and they are really tumours of sweat glands around the eyelids and this is a very dramatic example from a paper that a case series that we published on the subject. One more eyelid problem that we often see in kittens is neonatal ophthalmia.

As we know, the eyelids are supposed to open at around 12 to 14 days of age, but sometimes you will get Get microbial infection of the globe and the ocular surface even before the eyelids open and here is a clinical sign that it's happening that there is a nasty. Infection brewing underneath these eyelids which are still adhered and such an infection may cause sympleferon, adhesion of the cornea to the conjunctiva, or it may even cause corneal perforation and the kitten by the time it opens its eyes may have lost its eye. And therefore, this should be treated as an emergency and the best treatment is to open the eyelids, but I stress the word manually.

We open them manually. What I don't want you to do is to take scissors and try and cut along the Elid line across the suture line of the two eyelids because I guarantee you that you can't cut it in a straight line, perfect and top line, and you are almost guaranteed to cut one lid or the other. What you should do is just manually grab the upper and lower eyelid and try to tease them apart, pull them apart, and because there is a natural line between them that's meant to open up in a day or two, May be able to open it.

If you're unable to open it, please insert an IV catheter here through this small opening, flush it, provide topical antibiotics, provide lots of artificial tears, repeated flushing daily until you are able to open the eyelids or Mother Nature opens them for you. But please treat these cases very seriously, otherwise you could end up with a blind, kitten. Moving on in our internal journey from eyelids and eyelashes, to the conjunctiva and the third eyelid, I think this is a classic case of a dog is not a small cat.

I actually gave an entire webinar about it 6 months ago that you can watch on the webinar vet. Archives, if I'm to summarise those 45 minutes in one sentence, in dogs, it is usually a secondary inflammation. There is something irritating the eyes, such as an eyelid problem, entropion, ectropion, maybe an eyelash problems such as the stickerassis.

Maybe there is dry eye, something is irritating the eye and Enabling overgrowth of normal flora and secondary infection, whereas in cats, it's a primary disease caused mostly by herpes with stress playing a big factor in the pathogenesis of this disease. As I said, it's a full 45 minute lecture that you can watch on the archives. So, moving on from the conjunctiva, which is discussed extensively elsewhere on to the third eyelid.

As you know, we often see cherry eye in dogs. We hardly ever see cherry eye in cats. When we see a lesion that looks like a cherry eye in cats, you should suspect a third eyelid tumour.

In fact, this is a lymphoma. I can already get an indication from this picture that this is a lymphoma and not a cherry eye. Number one, because it's on the wrong side.

Here is the 3rd eyelid on the nasal side and here is the lesion on the lateral side of the eyelids and a cherry eye as seen here, is supposed to prolapse behind the 3rd eyelid. Here is the 3rd eyelid and here is the cherry eye popping up behind it and you can see that this lesion is not popping up behind the 3rd eyelid. So the loca the lateral location and the fact that it's in front of the 3rd eyelid leads me to suspect that it's not a cherry eye and in fact, it's a lymphoma.

And just a month ago, I've had one of the most horrifying cases I've had in a long time. Whereby a dog showed up in our clinic, a month ago, it underwent cherry eye surgery to replace a cherry eye by a referring a vet. And one month after surgery, he comes back with exophthalmus.

We did ultrasound, we noticed a retro bulbar mass. We bio we took a fine aspiration and we found heangiosarcoma. And what we strongly, strongly suspect is that what the referring vet thought was a cherry eye one month ago was in fact man.

Sarcoma, it could have easily been removed surgically. Instead, the vet pushed it back into the orbit and now the dog has got retrobulbar hemangiosarcoma with optic nerve involvement and a very, very bad prognosis. So no matter if you're talking dogs or cats, please always make sure you're replacing a cherry eye and not a tumour.

One more disease I should mention in the context of the third eyelid in cats is what we call Hall's syndrome, which is idiopathic bilateral third eyelid protrusion. Gosh, we've got so many idiopathic diseases in cats, don't we? Not just in eyes, but also in eyes.

Some people suspect that there is viral involvement, maybe a GI disease, maybe it's a problem of sympathetic denervation. Which is why some people treated with epinephrine, but there are no studies showing us that it's really efficacious. There are no studies proving conclusively that it's a GI disease.

Basically, it's a self-limiting disease and you can tell the owners that It will go away in 6 months on average. However, of course, when you do see a cat with bilateral prolapse of the third eyelid, don't forget to check it for other possible causes of bilateral third eyelid prolapse such as dehydration or weight loss, cause if it's that weight loss, you certainly want to work up the cat. Moving on from the conjunctava and third eyelid onto the lacrimal system, here is another difference for you between dogs and cats when talking about dry eye.

In dogs, as we know, dry eye is usually caused by autoimmune inflammation and it's inherited in Some dog breeds, which is why cyclosporin and tacrolimus immunomodulating drugs are such effective therapies. In cats, it is an acquired disease secondary to herpes infection. And really the herpes virus causes .

Dry eye by several mechanisms. Number one, it directly attacks the tear glands causing inflammation of the tear glands, adenitiss, just like the distemper virus in dogs causes adenits of the tear gland and dry eye in dogs. Herpes virus causes adenittis of the tear gland and dry eye in cats.

As if this wasn't enough, the severe conjunctivitis that we usually see in cats with herpetic infection may cause scarring of the ducts that drain tears from this tear gland onto the eye. And finally, The cat is not blinking as often as it should blink because of damage to the trigeminal nerve caused by the herpes virus. You may recall from my previous talk that the herpes virus has a tropism to the trigeminal nerve.

That's where it remains latent and that's where it becomes activated, following stress. So herpetic infection does cause trigeminal damage. I know if you're.

Of this, but when we blink, the trigger for blinking is because we feel that our cornea is drying up. So we need trigeminal nerve, a functional trigeminal nerve to tell us that our cornea is drying and it's time to blink. If you have trigeminal nerve damage, you are not blinking as much.

So these poor cats produce fewer tears because of damage to the gland. What few tears are Produce have a hard time draining onto the corneal surface because of damage to the ducts and once they drain onto the ocular surface, they are not spread by blinking because the cat is not blinking as much. All of these combined into very severe dry eye in cats, and as if this wasn't enough, there is also what we called qualitative dry eye in these cats, .

Goblet cells in the conjunctiva that are responsible for producing mucin, the innermost layer of the tear film that is responsible for spreading the tear film on the eye are damaging conjunctivitis. We get mucin loss and we get Qualitative dry eye in addition to the quantitative dry eye that you're seeing here, and here is a picture of dry eye in a tad. You can tell it's dry eye just by the dull reflection of the camera flash.

Unfortunately, it's challenging to diagnose dry eye in cats because, there is such a huge variation in normal tear production values. In dogs, it's easy. We do a shimmer tear tests, we say anything below 150 millimetres per minute is suspicious.

Anything less than 5 millilitres per minute is a definitive diagnosis of dry eye. In cats, and I'm talking about. Domestic cat, not about this line, you do a Shimmer tier test and in normal cats, it can range anywhere from 9 to 34 millimetres per minute.

PRTT and all red tier test. It's another test strip similar to the Shimmer Schmer test strip, but it's much thinner and therefore, this test lasts only 15 seconds versus the 60 seconds of the Schmert test, but you can see. Again, huge variation in normal results and also in the tier film breakup time test that measures the quality of the tier film.

Again, huge variation. So it's difficult to diagnose dry eye in these cats with the tests that we would normally use in dogs and instead, the diagnosis is based on history of herpes infection and on the clinical signs that we see in these eyes. Not only is the Diagnosis of dry eye in cats challenging.

The treatment is very challenging because, as I said, we have very effective immunomodulating drugs for canine dry eye, but here we're talking about damage to the tear gland, and damage to the trigeminal nerve and the ducts. We don't really have a very good and effective way of treating them. And the most we usually can offer this patient is just artificial tears, rich in hyaluronic acid to replace the lost goblet cells.

Yes, people have tried cyclosporin, and tacrolimus, and ylocarine, and even parotid duct transposition in these cats, but we don't have. Studies that show that these treatments are efficacious. So once again, all we can offer the cats is artificial tears, but I do stress that yes, every cat with herpetic conjunctivitis or herpetic kerato conjunctivitis should be supplemented with With, with artificial tears, we always remember to give antibiotics in case of chlamydia.

We'll always remember the antiviral drugs. Many of us forget the artificial tears, they will make a huge difference in the comfort of the patient. Please provide them to your patient.

So we discussed the problems of tear production in cats, but just like dogs, cats also have tear drainage problems, and I'm sure you've all seen these cats with a tear stain along their face, just like we see it in dogs and just like in dogs. When you see an overflow of tears, it may be due to increased production cause something is irritating the eye, but I said earlier that dyychia and entropion and those diseases that cause irritation of the canine cornea and cause tear overflow in dogs. Are quite rare in cats.

So usually in cats, this is a drainage problem. There is no production of tears, but drainage is blocked, which is why we get this, facial staining syndrome, especially in brachycephalic cat treats. And we also see these tear stains in black encephalic dogs such as this bulldog here.

But once again, there is a big difference between the cause of the tear stain in between dogs and cats. In dogs. The miniature breeds, the bracephalic breeds, the tear stain that we're seeing here is usually caused by a slight medial entropion.

And when you have a medial entropion, number one, the eyelashes there are irritating cornea, but number 2, it causes aversion of the nasolacrimal. Puncta, or I should say inversion of the nasolammon puncta, it doesn't drain tears as much and tears instead of draining into the nasolacrimal duct, they stain the face. And this can therefore easily be corrected with a simple entropion surgery.

So again, if you're seeing dogs with this presentation, look for the nasal entropion and you can easily correct it. Cats, the same presentation, but the reason is completely different. In cats in block cephalic breeds, because of the short nose, the length of the nasolacrimal duct is much shorter and right at this point, it Actually makes a 90 degree turn.

There is a kink here, so this is a dole cephalic cat and this is a brackycephalic cat. You can see the short nasolaromal duct, the 90 degree turn here which leads to kinking and shutting down of the nasolacrimal duct, which is why tears are draining onto the face of the cat. So theoretically, you could do a surgery to create new drainage pathways if the nasollamal duct is blocked and you can see people drilling drainage pathways into the .

Nasal sinuses or new drainage pathway into the oral cavity. And here is what the cat would look like post-surgically. However, this is a picture I borrowed from my teacher in Florida, Dennis Brooks.

This is a Surgery that I would perform cause I'm asking myself whether I am actually helping the animal or just doing it to please the owner for cosmetic reasons cause the cat is really not bothered by this tear stain. You just need to instruct. Owners to clean it frequently to prevent secondary dermatitis, OK?

But it's really more of an as long as you keep it nice and dry and clean, it's more of an aesthetic problem, so I wouldn't advocate such a radical surgery to resolve what is really a cosmetic problem. And people would always ask why is it brown, and that's probably because of iron contents in the tears. And as I said, it bothers lots of people and where there is a demand there was always someone who would come up with a solution.

So here is a solution. I tear stain remover for cats and actually I call it medications quote unquote cause on the internet today you can sell anything without any proof that it works. I was actually a couple of years ago at a large veterinary meeting in Orlando in Florida and I saw the booth of the company producing this product, so I walked up to them and said, Gee whiz, maybe perhaps you can finally tell me how this product works.

And he starts talking and I listen to him and after about 45 seconds, he stops and says, what are you practising? And I say, I say I'm an ophthalmologist. He says, I'm ophthalmologist, sorry, I can't explain it to you.

OK, so yeah, he, he can, he can sell it to others, but he can't sell it to ophthalmologists. We don't believe that it works. Moving on from the lacrimal system to the cornea, well, as I said, Feline keratitis, feline kerato conjunctivitis is usually caused by a feline herpes infection and in fact the involvement of the cornea is what differentiates between feline herpes infection and lay.

Lydia infection, that's how we can tell that this cat with the corneal ulcer actually has herpes and not chlamydia and requires antiviral treatment. And again, I invite you to watch the webinar that I gave 7 months ago on the subject. We do have in the cornea a number of, on the feline cornea, a number of diseases that we see only in cats or almost only in cats, and they are listed here.

However, to learn all about them, I invite you to my upcoming webinar next month when we'll be talking about unique diseases of the feline cornea, which means that I can move on to the iris and The lesion, the lesion I want to talk about is intraocular neoplasia of the iris, in dogs as well as in cats, whenever we are presented with an elderly patient and unilateral uveitis or unilateral glaucoma, we do need to consider neoplasia as a leading differential. The eye, just like any other organ, can suffer from primary tumours or from secondary tumour. And if it's primary tumours, then the two leading primary tumours in a cat are diffuse iris melanoma, which is what you are seeing here, or intraocular sarcoma, and both of these tumours are very, very lethal and carry a very bad prognosis.

Again, unlike dogs where melanoma is a very, I wouldn't say benign tumour, but very slow. It is mostly benign, very slowly progressing, hardly metastasizing, and the dog can live happily ever after with a small iris melanoma. It's definitely not true of cats.

And if we're talking secondary tumours, metastasis into the eye, then lymphoma is the most common metastatic tumour in the eye. So when you diagnose lymphoma, you do have to consider multicentric disease just like in any other species, but in cat, of course, it is a suggestion that maybe the cat is also infected with FELV or with FIV. But I want to talk a bit about the diffuse iris melanoma, which poses a great clinical challenge to us, because it can have a huge range of presentation all the way from the small lesion here to this huge lesion here.

And the question is what do we do? Do we monitor it like a We would monitor a melanoma in a dog or do we nucleate it because of the high metastasis rate that I mentioned. So if I look at this eye here, this eye is definitely to be scheduled for surgery.

We can see widespread iris, melanoma, we can see pigment on the interior lens capsule, which means there is already secondary uveitis, perhaps there is even secondary glaucoma. I would suspect cause I'm seeing a bit too much of the sclero conjunctiva here. This eye definitely has to come out.

But what about this eye? This is a real dilemma because it's just a small lesion, otherwise, the eye is perfectly fine. There is no uveitis, there is no glaucoma.

Am I to take out a perfectly normal eye because of this one lesion? I mean, for us ophthalmologists, nucleation is analogous to euthanasia, you know, I'm killing my patient. I can't kill my patient because of such a, a small lesion.

But I want to catch it before it metastasizes and kill the cat. And it's really a big, big dilemma, and I'm showing you again here a wide range of presentations all the way from a small lesion here to small diffused lesions here and you can see various presentations and it's a true dilemma, not just To you and me, here is an amazing, study that was done by the University of California Davis. Unfortunately, it was only presented as a meeting abstract.

It is yet to come out in the paper. What they did here was take pictures of 6 cats, 3 of them had melanocytoma, 3 of them had diffuse iris melanoma. They knew the diagnosis because they had histopathological confirmation on all 6 eyes, OK.

They sent out those 6 pictures to 100 ACVO dilomates. 100 specialists who practise full-time ophthalmology, boarded ophthalmologists, with lots and lots of experience and ask them to decide whether it's a melanocytoma or whether it is a melanoma of the 100 people, 76 wrote back. And again, if this was live recording, I'd ask you how many of the 76 got all 6 pictures right?

And the answer is 2. OK. Just 2 specialists out of 76 were able to correctly guess all 76 pictures, which means really that there is no way for you to look at an eye and decide on whether it's melanoma or not.

I had an old teacher who used to say you can only make A histopathological diagnosis using histopathology. It's impossible to look at an eye and decide what is the lesion. So we bring them to lots of frequent visits to monitor and if we see secondary glaucoma.

If we see a mass infiltrating the angle such as we are seeing here, if we are seeing changes in the shape of the pupil, in the motility of the pupil, if we are seeing an increased number of masses or if it's spreading or if they're elevated, then it is time to remove the eye. You could try and sample aqueous. But it's got low diagnostic yield, so it's possible for us to take an iris biopsy.

Here is a paper from the United Kingdom, describing the iris biopsy. We actually go in with small scissors and take a snip and send it to pathology. It is a big dilemma.

We don't want to nucleate nor a melanocytoma, but we don't want to leave a melanoma in place. And my last topic is cataracts, glaucoma, and everything else. And really, really the leading cause of blindness in cats is Uveitis.

It's a subject that again was covered in my talk on a June 17th and actually I see that I have a mistake cause I told you that also my keraitis talk was given June 17th, so one of the dates is wrong for which I apologise and, but I'm sure you can find both talks in the archive White Cats Go Blind and feline conjunctivitis. . But anyhow to recap what I said at that talk, the four leading Causes of feline uveitis are toxoplasma, FIP, FIV, and FELV.

As I said, you always have to consider neoplasia in cases of unilateral UVIis in elderly cats, but unfortunately, the most common cause of feline uveitis is idiopathic. Often we are unable to discover the cause of UVI. And I say that UVitis is the leading cause of blindness in cats because of the numerous complications it causes, 15, 1/3 of cases end up with cataract, and that's because the lens depends on aquisumer for metabolic support.

And when the composition of aqueumer changes new VITs, the lens loses the metabolic support and develops a cataract. There is lots of secondary glaucoma, 1/4 to 1 half of the cases due either to obstruction of the drainage angle by the Inflammatory material floating in the interior chamber or because of adhesions between the iris and the interior lens capsule, posterior sinicia leading to iris Bombay or because of retinal degeneration in up to 70% of the cases. And this slide here really.

Can be summarised as another significant difference between dogs and cats because in dogs, all of these diseases are hereditary, or many of them are hereditary, OK? So cataracts, the two leading causes in dogs are diabetes and inheritance, glaucoma. Half the cases we see in dogs are hereditary.

Retinal degeneration, PRA, very common hereditary disease in dogs, OK. So all of these are commonly hereditary disease in dogs, but they are secondary diseases in cats, secondary to uveitis, which means that all cases of feline glaucoma or feline cataracts that you see should be worked up for. Causes of UVITs, the, because UVIis is the most common cause of feline glaucoma and of feline cataracts, then you should work up these patients for Toxo, for FIP, for FIV, for FELV and again, I, this is discussed at length at my other lecture on why cats go blind June 17th or some other time in 2021.

One last disease I wanna discuss as a cause of blindness is optic neuritis and here is a study list describing findings in '96. Dogs with optic neuritis and you can see that the most common causes of optic neuritis in dogs are idiopathic or MUE Meningoencephalitis of unknown aetiology or GME. So, an idiopathic or an immune disease, as you can see, neoplasia and immune and infections are relatively uncommon causes of optic neuritis in dogs.

Cats, we have a different picture because we don't have idiopathic optic neuritis, we don't have immune-mediated optic neuritis in cats, optic neuritis is due to systemic infectious diseases, usually spreading from the orbit or from the nasal sinuses or hematogenously and if you see a cat with Optic neuritis, you should work it up for FIP, Toxo, crypto, or histo as described in this paper here. How do we sus, what makes us suspect optic neuritis in a cat? Well they will present with acute blindness and fixed dilated pupils.

And again, even though the cause may be systemic, they will show up with the ophthalmic complaint, they will show up complaining of blindness. It is really a symptom. Of a systemic disease as I said.

And if you look at the fineness of this catch, you can see changes in the optic disc. You can see edoema of the optic disc, congestion, see how dark this disc is, you may see haemorrhage on the surface of the disc or edoema and detachment around the discs such as you're seeing here. Optic neuritis should be considered a neurological disease due to a systemic infection.

So you work it out by performing a comprehensive physical or phallic neurological exam, send blood work for blood count, biochemistry and serology for the. Agents I mentioned and definitely consultant neurologist who may do CSF and advanced imaging. Here is an MRI picture showing you a normal optic nerve and an extremely swollen optic nerve in the case of optic neuritis.

If you are lucky enough to find the primary cause, treat it, for example, if you're lucky enough to find Toxo or crypto as primary cause, then yes, you can treat with clindamycin or with antifungal agents and the prognosis improves. If not, you should try immunosuppressive treatment. With prednisolone, mycophenolate, azathioprine, oral cyclosporin, etc.

Etc. But if you haven't found an underlying cause, the prognosis is guarded to poor. Again, this would be a typical presentation of a blind cat with a fixed dilated pupil and look at the massive inflammation of the optic nerve head.

There are other causes of blindness in cats that are different from dogs, hypertensive retinopathy, a leading cause of blindness in elderly cats due to systemic hypertension, usually induced by chronic kidney disease or by hyperthyroidism. So-called PRA or inherited rectal degeneration, very common in dogs, but very rare in cats, and we have a number of rare and unusual causes of blindness in cats that we don't see in other species, dietary thine deficiency, androfloxacin, toxicity, I should say here, not deficiency, sorry for the spelling mistake. Mouth gags used during dental cleaning may cause ischemia of the maxillary art.

And cerebral blindness and a nucleation surgery, if you try and clamp on the optic nerve as you're removing the eye, you may end up clumping the opticiam and causing blindness in the contralateral eye. All of these are discussed in my previous webinar and I remind you once again to please join me next month when we shall be describing a list of other Corneal diseases that are unique to cats. So, I wish you happy holidays.

I hope that you and your family remain safe and healthy and I look forward to seeing you next year. Thank you very much.