Hello, everyone. My name is Ron Offrey, and I'm a professor of veteran almology at the Hebrew University of Jerusalem in Israel. I've been talking at the webinar vet for a number of years, and I think I have over 20 lectures in the archives of the small animal practitioners, but this is my first lecture in the equine stream.

I'm very happy to have the opportunity to talk to you, and talk to you today about making sense of the ophthalmic exam of the horse. As always, I want to declare that I have no financial relationship with any product that I would be mentioning, and I would like to thank Bailey's Horse Feeds for sponsoring this session today. Just to begin with a bit of literature, if you are interested in equine ophthalmology, here are two textbooks that may be of interest to you.

The one on the left, equine ophthalmology, edited by Brian Giler from North Carolina State University. As you can see, it's now in its 3rd edition. This is the bible of that of equine ophthalmology.

It is 680 pages long. A hardcover coffee table book size. It really contains everything you need to know about equine ophthalmology.

I'd say it's definitely high level, advanced level more for residents or veterinary ophthalmology practitioners, but really any question you have about equinophalmology, you'll find the answer in that book. The one on the right, It was written by my teacher Dennis Brooks, who are from the University of Florida, who is now retired, but at the time was really the foremost veterinary equine veteranmologies in the world. This is a pocketbook size and it's only 250 pages long.

So if you want a more concise review of equine ophthalmology, that's the book you want to purchase. And as I said, I have no financial relationship, but maybe a bit of shameless advertising in a textbook that I have co-edited together with David Maggs from UC Davis and Paul Miller from the University of Madison, Wisconsin, Slatter's Fundamentals veteran ofi. We do have a chapter devoted to equine of emoji.

Written by Mary Latin. She is a professor of equine thermology at the University of Pennsylvania. Right.

So, after this introduction, let us talk about the ophthalmic exam of the horse, and I know that people are somewhat apprehensive about performing an ophthalmic exam, and they are apprehensive for two reasons. The first is That they think it is a complicated exam. Actually, it is not complicated, as I hope you will see today.

I divide the exam into three parts. One is a gross examination looking at the horse from a distance without touching it. The second part is assessing the horse's vision, and then we examine the eye from the front, from the eyelids and the eyelashes.

All the way to the back, to the retina, and if you remember the anatomical order of the ocular tissues from the conjunctiva to the cornea anterior chamber, iris lens, etc. And examine them in an orderly anatomical manner, you will have performed a comprehensive othanic exam. The other reason that people are apprehensive about an orphanic exam is that they think, gosh, it's very expensive.

I need all sorts of fancy equipment, and actually, you do not need lots of expensive equipment. There is just one here is all you need for an authanic exam of a horse and really is just one expensive item here and that's the tonopin for measuring intraocular pressure. In small animals, we do have a cheaper alternative in the way of a shields, but unfortunately, it's unsuitable for horse eye.

But other than that, everything is really, Reasonably priced. We need a handle fully charged, and this handle will fit two instruments. It will fit your directive thermoscope, which we'll talk about at the end of my talk, and it will fit the thing of trans illuminator, giving you a strong focal source of light.

You need a handheld lens, some sort of magnification, a couple of eye drops, a couple of test strips, maybe swabs and fine forceps, and that's it, you are ready to go. In fact, the most important item that you need for an authentic exam of a horse is not shown in this picture, it is shown here. You need a dark room, OK.

Please do not try to perform an orphanic exam outdoors or in a lit stable room. You really need a dark and stable room, and in a dark room with a strong focal source of light that I mentioned earlier, the film of Transilluminator, you really can see 90% of what you need to see. The other 10% is all the fancy toys that sometimes we bring along, but really good focal source of light and a dark room, and you are in business.

You have everything you need for an orphanic exam. So as I said, the exam begins with a cross examination of the horse, and by gross, I mean that I'm standing at a distance. I'm not touching it.

I'm standing a couple of feet away and just looking at the horse and asking myself three questions. The first question I'm asking myself is whether there is evidence of pain. And in a horse, unlike small animals, we have a very sensitive indicator for pain, and that is the angle of the eyelashes.

In a normal painless eye, the eyelashes should be parallel to the floor, as you're seeing here. I'm sorry that the arrow is misplaced, but the eyelashes are parallel to the floor just stay as they are in my eyes and in your eyes. One of the earliest signs of pain in the horse is that the eyelashes are drooping and they are now vertical to the floor.

OK, so look at the orientation of the eyelashes and as I said, do it from a couple of feet away so you're not frightening the horse, not causing it to blink. That's also important because we look for. Squinting, we look for increased blinking, obviously you do want to compare it to the other eye as far as the squinting and the blinking rate goes, which brings up a very, very important point and that is.

The use of topical anaesthetic. Obviously, when I have such painful eye, I, I would need to apply topical anaesthetic in order to get the horse to open its eye. I also need to perform a motor block that I'll talk about later, but I will add a topical anaesthetic.

And as it says here, Toul aesthetics are diagnostics. They are not therapeutic, and I stress the word not because when you examine the horse, you put a drop of topical anaesthetic in the eye, the horse opens its eye, and the horse owner goes, My God, you're a magician! 5 seconds and you cure the problem.

No, I, as you know, I didn't cure the problem. Whatever caused the pain is still there. I just put a drop of topical anaesthetic in the eye and I'm stressing this point because the owner will beg you or threaten you or try to, to get the topical anaesthetic or steal from you.

They really want these magical drops. You are never to give them, you're never to prescribe them because, I hate to say it, but you know, pain is a clinical sign. We want to.

Know whether pain is improving or worsening based on the results of treatment, we do not want to mask the pain with top kill anaesthetic and worse, you know, the owners take these drops home and 6 months from now when the horse has another problem or worse when they or their child has an ocular problem, ah, they'll just pull out those magical drops, put a drop of that in the eye and think the problem has been resolved. So, 30 years in ophthalmology, I have never ever prescribed copy anaesthetic. Please don't make a mistake.

So as I said, I'm still standing at some distance from the horse, performing cross examination, looking first for evidence of pain. Second, I look for secretions. And if there are secretions, they may be of two types.

One, they may be. Tears such as we are seeing here in this horse. And if a horse is tearing, it may be for two reasons.

Maybe it's producing too many tears, what we call a cremation, and that's because something is irritating the eye, eyelash. Eyelids, foreign bodies will take a quick review of all the possible reasons in my talk today. So maybe there is excessive production causing tear flow, or the other scenario is that maybe tear production is normal, but tear drainage through the nasolacrimal duct is blocked and you'd want to check the patency of the nasal lacrimal duct.

The other type of secretions that you are seeing or you that you may see is inflammatory or infectious secretions, so it may be serious mucoid or purulent such as you are seeing here. And in the horse, we definitely want to collect culture and sensitivity because we are terrified of organisms such as aspergillosis or pseudomonas that secrete colagenases and proteases that degrade the equine cornea. So definitely we wanna take cultural sensitivity, .

I know that it is claimed in some places that you should take cultural sensitivity before putting a to anaesthetic in the eye, and that's because to anaesthetic contains preservatives, and it was thought that these preservatives may influence the results of the cultural and sensitivity, but actually we have a couple of studies. This was in dogs that we have similar. Studies in horses showing that this is not true, so you can take cultural sensitivity before or after applying the topical anaesthetic.

But please, as it says here, collect them in every case of purulent or infectious discharge. And the third question I'm asking myself, OK, after determining whether there are signs of pain and whether there is secretions, is looking at the size of the eye, again, maybe the relative size comparing one eye to the other, the symmetry in the appearance of these eyes, and you can see that obviously there is as symmetry here, and the left eye has. Some kind of problem, and I say some kind of problem because this can actually be one of two diseases.

Maybe there is almus here. Thalamus is an enlarged eye due to glaucoma. So maybe this eye is suffering from elevated intraocular pressure, or the other possibility is that it is a normal eye that is being pushed forward by a retroboulard disease process.

Maybe a tumour or an abscess caused pushing the eye forward and causing exopthalmus. So you may be challenged on how to distinguish between both almus and exothalmus. The golden standard would obviously be to measure intraocular pressure with the funnel pen that I showed you earlier and that diagnose glaucoma or a quick ultrasound will tell you if there is a retrovolar disease process.

So, after, after we've grossly examined the horse of the eye, the next step in the exam is to evaluate the patient's vision. And vision is most commonly tested using the menace response. You make a menacing gesture and You watch the horse blink in return.

Let us see a movie first. I hope it works. We just prior to the recording, and then I'll talk about the movie.

To perform the menace response, stand on the side of the horse and not directly in front. Make a quick, even threatening motion towards your horse's eye, stopping about 6 inches from the eye. Now compare the response to the other side.

Try not to create any air currents toward the eye because that too may elicit a reaction and confuse your assessment. Use your fingertips and not your whole hand to try to reduce air flow. Does the horse respond appropriately?

At minimum they should blink or they may even move their head in a defensive gesture. OK, so, two points from this movie, both of them trying to help you avoid generating a false positive response. False positive means positive.

The horse will blink because of the menacing gesture, but it's a false positive. It will blink even though it cannot see you. One reason for that is if you stimulate the contralateral eye.

This diagram here shows you the visual fields of a horse, and here is the visual field of the right eye, here is the Visual field of the left eye and as you can see there is an area of overlap between the two in front of the horse where you have binocular vision or input from both eyes. So as the movie was saying when evaluating menace in Horse, you want to stand on the side so that you are sure that you're only stimulating this right eye, because if you stand in front of the horse threatening the right eye, it may blink because the left eye saw you. OK, so avoid stimulating the contralateral eye by standing to the side of the horse and as the movie.

Try to avoid generating wind or air currents by using your fingers rather than a whole hand. Avoid touching eyelashes or facial hair. So avoid trigeminal stimulation cause that would also cause blinking even if the horse is blind.

Just like the test has a false positive, it also has a possible false negative. False negative means that the horse is not blinking, so it's negative, but it's a false negative. It's not blinking even though it can see you.

One reason for that is age. You see that menace is considered to be a response, not a reflex, meaning the, one definition of a reflex versus a response is that you are born with a reflex. But a response is something you have to learn, and a menace is a response.

The horse needs to learn that this menacing gesture is dangerous and that it needs to blink to protect the eyes. And generally, the test is considered useless before the age of 4 months, so, not to, in a very young horse or very young fold, it will generate a false negative. Another source of false negative is facial nerve paralysis.

The horse sees you. It wants to blink, but it is unable to blink because of facial nerve paralysis. So if the horse doesn't blink when you get make the medicine, gesture, you want to test the people reflex as shown here.

We touch the skin at the nasal and cancers and we try to elicit a blinking reflex due to trigeminal stimulation so that would, and if the horse is now blinking in response to trigeminal stimulation but not blinking in response to the test, then it's blind. If it's not blinking when you are stimulating it. With the palpibrol test, then it probably has facial nerve paralysis.

As it says here, we, there is indeed facial nerve paralysis and the horse is not blinking but is able to see you, the third eyelid would often come up, so that would also be a sign that the horse is visual. And since I mentioned the palpibr reflex, then as we said, the afferent pathway is the trigeminal nerve that provides sensory innervation both to the cornea and to the skin around the eye, and the efferent pathway is a facial nerve that causes the orbicularis oculi muscle to blink, and yes, facial nerve paralysis is common in horses. We can see here a study of 64 horses with facial nerve paralysis, and you can see here the most common causes would be trauma when the horse rolls around, it can frequently strike the head and damage the.

Facial nerve, central nervous system disease, and idiopathic. Not bad prognosis if the primary cause such as CNS disease or trauma is treated, then more than 50% recovery. Another way to assess the horse's vision is by an obstacle course, as shown here in this picture.

Two advantages to an obstacle course as opposed to a menace test. One is that you can do it in a lit in a dim environment, and that's important to diagnose some, diseases, for example, congenital stationary night blindness, and inherited disease. Theseapalusas and some horse breeds, as the name implies we're talking now about night blindness, so the horse will be blind in a dim environment while, but will be able to see in a li environment.

So, that's one advantage and as shown here, you can include one eye and assess vision in each eye separately. Moving on from cortical vision, would we also want to check the subcortical reflexes. And in order to do that, we begin.

3 of the pupils in the light and to do that, I stand again a few feet away. Remember, I'm still not touching the horse and still get some. I turn off the room light, and I want to see both pupils dilate in a symmetric fashion.

And if they do, I, that's great. If they don't, if they're anisocoria, as you can see here in this case where we have anisocoria, the right pupil is larger than the left pupil. Well, in such case, obviously you need to determine which of The two pupils is abnormal because it may be this pupil that's problematic.

It may be this pupil that is problematic. And in order to determine which of the two is the problematic pupil, we compare the magnitude of anisocoria both in the light and in the dark. So if there was anisooria in the light and I turned off the room light and the amount of anisochoa decreased, then the metriatic pupil was abnormal cause in the light in the dark, if this pupil expanded, that means that, or I should say the pupil dilated, excuse me, then the amount of anisochoa decreased, that means that this one was the abnormal one.

On the other hand, if in the dark the magnitude of the onus of Correa is increasing, then the meiotic one was the abnormal cause this one kept on dilating in the dark. This one did not. OK, so that's a quick and easy way to determine which of the two pupils is abnormal.

And once we have looked at the size of the pupils, we obviously check to see whether they constrict in response to light and as you know, we checked both the direct PLR. The constriction of the stimulated eye, but we also check the consensual PLR, the constriction of the non-stimulated eye. And another very important subcortical reflex is what's called dazzle reflex, whereby we take a strong source of light as shown here and shine it in front of the horse's eye, and we want to see the horse blink in response.

Now, again, I am now talking about a subcortical reflex. So the fact that the horse would blink as a result of this flashlight being aimed at its eye doesn't mean that the horse is visual. I am testing the integrity of subcortical pathways, but nonetheless, it is a very, very important diagnostic test cause.

The dazzle and the indirect PLR allow you to Evaluate retinal function if you cannot see the fundus. For example, here is a horse eye with severe corneal edoema and some high femur. I cannot see the pupil, so I can test the direct PLR in this eye.

I have no idea if the retina in this eye is functioning or not. However, if your some source of light, test a dazzle reflects who she's supposed to be. Take your strong source of light.

Look at the other pupil. It is the most constrict, OK. So when you're unable to see the pupil, is perform the indirect PLR test and the dazzle reflex test in order to know whether or not the retina is functioning.

However, I said the retina is functioning. It doesn't necessarily mean that the horse is visual, and that's another very important point. Normal PLR and dazzle do not imply vision.

For example, here is a horse that's obviously blind. It's blind with advanced cataract. It is unable to see, but take your strong source of light, place it next to the eye, enough photons will get into the eye to trigger a pupillary light reflex.

So really minimal stimulation is needed for the reflex and PLR is also present in animals with advanced cataracts such as this one or retinal degeneration. So this is one example why. The presence of a PLR doesn't necessarily imply vision.

The other reason is shown here in this diagram, showing that the visual pathways providing input for the PLR and cortical vision run together through the optic nerve, chiasm, and. Proximal part of the optic tract, but here they diverge, and these are the fibres, the thin line are the fibres providing afferent input to the PLR. These are the fibres providing afferent input for vision.

So if there is cortical disease. Here, localised to this part of the visual pathways, then you will have PLR because these fibres have already diverged and are not affected, but the animal will be blind. So an animal with cortical blindness, PLR will be normal, but nonetheless, these are very important tests to give you an idea of retinal function.

And a final point when talking about the subparticle reflexes is the point of I mentioned again again but I want to emphasise it now, you need a strong source guide, you need a fully charged. Of transluminator as shown here. Please don't test the PLR with some silly LED that you've got on a keychain or something.

It's not strong enough. The number one reason for lack of PLR is the veterinarian not using strong enough source of light. In fact, we get animals referred to.

For not having PLR them with our slit lamp or spin off and turns out that the PLR is normal. Turns out that there was no PLR when it was tested by veterinarians because they didn't have a proper source of light. So please save yourself this embarrassment by using the proper source of light.

Right, so we've spoken about the cross examination of the horse. We've spoken about assessing vision, both cortical vision and the subcortical reflex, and now it's time to move on to the Examination of all of the ocular tissues. But before we do that, I remind you that eventually we'll want to check to examine the lens and we want to examine the fundus which come at the very end, but we need the pupil.

Dilated in order to perform a comprehensive exam of the lens to see if there is caract and a comprehensive exam of the retina. In order to do that, we dilate the pupil with tropeomide, which is a fast and short acting parasympathletic drug. Fast means that to dilate the people within 20 minutes, short acting, meaning that by evening time, the pupil will be back to normal.

You do not dilate the pupil for diagnostic purposes with atropine, another paralytic drug, but atropine is slow acting and long-acting. By slow acting, I mean that it takes an hour or two for the people to dilate and you. Don't want to wait an hour or two, and it is long acting in a normal eye.

The half-lifetime of atropine is 4 days. OK, so the owner will definitely be upset with you if you've dilated the pupil for 4 days. Atropine is used only for therapeutic reasons in cases of UVis.

The diagnostic dilation is obtained using tropekomide. The problem is that tropikomide decreases tear production. Just like it decreases secretions everywhere, being a person athletic drug, it increases IOP because it dilates and closes the corneal drainage angle and it will block the PLR because once you have a dilated pupil, pharmacologically dilated, it will not constrict.

And therefore we begin an ophthalmic exam once I finished the Gross examination, and once I have finished testing vision and the PLR, I begin by checking the Schirmer tear test, the IOP, and the PLR. Put a drop of tropekamide and now actually I have 20 minutes to stand, chat with the owner about the history, perform a physical exam, examine the interior segment of the eye, and 20 minutes you could dilate, OK? So again, The order in which I'm performing an exam is before even talking to the owner, just do your cross examination looking for.

Excuse me, looking for signs of pain, looking for secretions, looking at the symmetry of the two globes, assess vision, assess the PLR, put in, sorry, measure these three tests, put in the tropeomide, and now you have your 20 minutes. And I call these three tests really the TPR of an ophthalmologist, you know, that basically we have TPR as in we take temperature, pulse and rate. Well, you know.

We begin the exam, as I said, by testing tear production using tier by tear test. We measure intraocular pressure going toometry, and we check the reflexes, the PLR, the direct and indirect PLR as I described earlier. So again, we, after doing my brief examination, the cross examination and assessing vision, I'll measured tear production, placing a Schumer tear test in the for of the lower eyelid.

Normal values in the horse are supposed to be 19 to 29 millimetres per minute, anything below. 19 millimetres per minute is diagnostic of dry eye. I know I'm speaking mostly to a British audience, so I'm very happy to give credit to Sheila Crispin, one of the leaders and founding, founder of veterinary ophthalmology in Europe and a great, great veterinary ophthalmologist.

When examining the tear film, we don't just measure it quantitatively looking at schmer tear test, we also look at the quality of the tier film, and that's because the Schmer tear test tested the aqueous portion of the tier film, but we may have diseases that affect the production of the lipid layer. And of the mucin layer and if there is an abnormality in either one, then the tears will evaporate very, very quickly. And here is a nice review paper by Frank Olivier talking about qualitative and quantitative in disorders in the horse, and you can see in these two eyes how in this eye you have a bright focused.

Reflection of the camera flash and here it is dim and diffused because there is dry eye. So look also at the quality of the tearing. Next, we measure IOP.

As I said, it is important to diagnose glaucoma. It is also when IOP increases, it's also important in the diagnosis of Uis where IOP decreases, normal pressure in the horse is around 23, 25 millimetres from mercury. It can be measured either with the amination tunnel metre that I showed you earlier or with the rebound tunnometer that's shown here in the picture on the right.

Then we check the PLR as I have described previously and now we can propotropicamide after testing IOP and PLRs, we can talk to the owner, take the history, do the physical exam, and Begin finally our ophthalmic exam. However, a couple of very important points to remember about the ophthalmic exam of the horse is that if the eye is painful, the horse may not be cooperative and therefore we would frequently have to sedate it systemically with whatever it is you're using and you may also need to perform a motor block of the upper eyelid in order to prevent the horse from blinking because it's very painful eye, then . You may not be able to get the horse to open its eye.

This shows you the location of the of the block. We are blocking the iclopibral nerve branch of facial nerve 7, and here we are palpating it. Basically over the frontal diplomatic process of the frontal bone as shown here right about this point, we palpate the nerve, we can actually feel it as a subcutaneous tendon running across here.

And we inject 5 millilitres of lidocaine subcutaneously around the nerve and that should give you great motor control. I mentioned earlier that in addition to systemic sedation and in addition to the motor block, we may need to apply topical anaesthetic. Here is a study showing us, from Iowa State University showing us the relative efficacy.

Of various popular anaesthetic in the horse as you can see here, mepivacaine doesn't give you complete anaesthetic who abupivacaine provides the longest duration of an anaesthetic, up to 60 minutes, and that may be too long. Most people will give. Half of 2% lidocaine either directly spraying onto the eye or through the sample fibral lavage system.

And we now can continue our examination and I remind you that at a certain point we did turn off the room light in order to watch the dilation of the pupils in order to test for the PLRs. Well, room lights have been turned off. Now you are continuing the exam in the dark.

As I said, darkness is our friend. I know it's counterintuitive and you think that in the final exam is performed in the light. No, we perform it in the dark with some sort of magnification and you will see it much better.

So, beginning our anatomical journey with the eyelids, basically we are looking at the eyelid margin and go take a look at the mirror or take a look at your horse or cat. You want to see the eyelid margin in firm contact with the globe, with the cornea. Here is a horse.

Where I simply can't see the eyelid margin. Maybe I see a bit of it here, but I'm not seeing any eyelid margin here, and that's because it's inverted, it's rolled inwards. We are talking about entropion, a common that's a problem that's very common in dogs because it's inherited in many dog breeds.

Horse, adult horses, it is less common, but it is common in sick folds because they are dehydrated, they are emaciated and therefore, they lose tissue in the retro bulbar space and the eye sinks into the orbit and then the eyelid rolls inwards. This sort of entropion is treated by attacking, not by surgery, because as I said, it is due to a systemic problem when the fall heals, when it starts, when it rehydrates. When it starts gaining body weight, it will resolve.

So if you did do surgery, you will have caused an ectropion. So please treat it with temporary attacking either staples or with skin sutures. And While looking at the eyelids, obviously you want to check for additional periocular lesions.

Maybe there is the varieties such as you're seeing here, maybe there is squamous cell carcinoma. Yes, this small ulcer is squamous cell carcinoma. I hope you know that we treat all.

All eyelid ulcers, especially in white horses such as this one, with great respect and we'll take a psychological scrape from this ulcer here cause in fact it's quaal carcinoma and here is a case of sar sarcoid. So look at the periocular tissues and you look at the eyelid margin. Next behind the eyelid margins, we have the eyelashes and As I've said here are the normal eyelashes, which are usually parallel to the floor, but sometimes we have abnormal eyelashes, dysthychia originating in the my boing land.

Now, the horse usually has a dark iris and dark hair, and you'd be very challenged to see these extra eyelashes against the background of a dark iris. So as you can see what we're doing here is retracting the eyelids slightly so that now we can see these eyelashes against the background of the whitish pinkish contava, OK. So if there is evidence of pain.

You are looking for dyschia, we track all four eyelids, both eyes in order to look for dyicchia, and this is actually a picture from a case we've had in our school a couple of months ago, and we treat it with thermalcalery. You can see the location of the mybomin gland here really. The hair is coming out here, but the follicle is in the mybomian gland where the thermocalery is point.

Next, we continue our journey. OK, we started with the eyelid, eyelash. We move on to the conjunctiva.

As you know, there is conjunctiva lining both the inner aspect of the eyelids and the interior aspect of the globe. And you all know what a normal conjunctiva is supposed to look like. And if it's not normal, ask yourself, is there edoema, which we call chemosis, maybe there are congested vessels, red eye, or other signs of inflammation.

As I said, you want to examine both the And people conjuntaiba looking at the inner aspect of both eyelids and you want to check the bulb or conjunctiva which is lining the interior aspect of the globe looking for them, looking for congestion and this picture shows you that you may be easily confused sometimes what looks like an inflammation is. Lymphoma in and therefore culture, cytology and biopsy may be needed if this horse doesn't respond to your usual anti-inflammatory treatment, you may to see if there is resistant bacteria. Maybe take a psychological scrape to see if there is fungal agents or maybe a biopsy to know if there is lymphoma.

Next, continuing my journey, I move on to the cornea and obviously the cornea is supposed to be transparent. If it's not transparent, you should ask yourself what caused loss of transparency? Is there vascularization such as you can see in the periphery here, is there corneal edoema, which we can see here, the blue haze abscess that I'm seeing here, ulcerations, cellular infiltration, etc.

Etc. And one of the very important points in this context is that every eye that exhibits signs of pain should be stained with fluorescine as shown here in order to detect a corneal ulcer, and that's because We treat the ulcers with great respect and we need to treat them medically or surgically very aggressively if we don't want the horse to lose its eye. Another indication for fluorescine is what we call a yel test in order to determine if there is corneal perforation.

Here is another o looking eye. You can see the peripheral cornea seeming more or less normal, but look at the centre, which is sort of gelatinous. It's got some pigment here, some tissue.

This is actually an eye that perforated. I hope the movie is playing, sorry, it's not playing. I'm sorry about that, but look up on Google the site Del test in order to see if a cornea is perforated or not.

And additional diagnostic tests you should run on every ugly looking cornea such as the one you saw in the other picture is cytology and culture. Cytology is taken using either a Brush such as you're seeing here, special spatula or the this end of a blade, and here is a study out of the University of Florida actually comparing the cytological yield of these three techniques in horses with ulcerative artitis. And what I like about this study is that it shows you that the cheapest one is the best, the scalpel blade provided the greatest.

And you can use it to see either bacteria or fungal hye. However, in order for the scrape to be diagnostic, you really need to scrape the cornea vigorously. I know that people are slightly afraid.

Oh my gosh, it's cornea. Don't worry, a scrape with the distal end of the day will not damage the cornea, but you need to scrape it vigorously if you are to reach a cellular diagnosis. Next, after the cornea, we examine the anterior chamber and the aquium and just in the cornea, the aquiumor of the interior chamber is supposed to be transparent.

It loses its its transparency in cases of inflammation of uitis when there is leakage of inflammatory materials such as platelets or protein into the aqueous humour. The best analogy I can give you for that is, if you go into a movie house and it's dark, the movie hasn't started yet, and then the projector in the back of the room comes on, all of a sudden bright light, you look up and you see all these dust particles floating in the room. You didn't see them before.

They're made visible by the strong light of the movie projector. Same with the eye, we can see the Inflammatory material floating in the eye with a strong beam of light as shown in these two pictures. Let me begin with the picture on the left, which is a non-inflamed eye.

Here we are using a slit lamp, so a very fine slit of light, and you can see the slit on the cornea, and maybe on the eyelid margin here, and another beam of light projected across the cornea and the iris. Everything in between them, which is the equi tumour in the anterior chamber, is dark because there are no inflammatory particles here as opposed to this inflamed eye where you can see the front state on the the. Cornea and third eyelid and eyelid, you can see the inner beam on the lens and the iris and everything between them that was found previously is now lit up by the slit of light just like the projector in the movie house lights up the dust particles.

So we are really seeing a wist there due to the presence of platelets. Protein and white blood cells, etc. In the interior chamber.

If you don't have a sleep lamp, don't worry, as shown here, you can use the smallest aperture of your direct phthalmoscope, and here is a picture and looking through it, you can see a transparent aquitumor or a not so transparent aquiummo. If you like the analogy of the movie house, I can give you another analogy. I once gave this lecture in China in the days when you could still enter China before COVID came along and they closed the borders, and after the lecture, we went to have dinner, and naturally we had beer, and then the guy sitting next to me says, Hey, here is your aquiz flair.

Filtered beer, unfiltered beer. No particles, yeah, plenty of particles. OK.

So here is a transparent aqueous humour. He is the aqueous humour of an inflamed eye. So if you can't remember the movie house analogy, I'm sure you remember the filtered versus unfiltered beer.

All these inflammatory particles that are floating in the eye in uveitis and sink to the bottom of the interior chamber, forming a hypopion here, another opion here, here you can see plenty of fibrine forming a clot in the interior chamber with some blood. All of these are signs of inflammation. Continuing on behind the interior chamber, we have the iris and again in the iris, I look for signs of inflammation.

Dark iris is probably inflamed, especially if it's darker than the other eye. And that's because it's congested. There is more, blood flow in UVI, so the iris is very dark.

The pupil is meiotic due to spasms of the ciliary body, or it may be regularly shaped because of adhesions. Between the iris and the interior lens capsule, all of the inflammatory material that I described earlier really acts as glue. The fibrine, the platelets facilitate adhesions of the iris to the interior lens.

And by now 20 minutes have gone by and the people is dilated and now we can continue our exam to look at the lens which is the next anatomical structure of the eye. Let me get my laser. Pointer back up, and the lens is supposed to be transparent just like the cornea due to the regular arrangement of the fibres here you can see there are nice parallel allowing light to pass through without being scattered.

So a normal lens is transparent, when it loses its transparency, why we have cataracts. Unfold, the most common cause of cataract is inheritance, and you definitely, if you're suspecting inheritance, you should avoid similar matings in the future. In adult horses, on the other hand, most of the cataracts are secondary to UVITs, which means that the horse requires systemic workup in order to determine the cause of UVI.

As I've said, in order to diagnose cataract, you want to dilate the pupil cause you want to examine both the nucleus and the periphery, so the pupil needs to be dilated and unfortunately, most cataracts are progressive in that what begins as a small opacity progresses to involve more and more of the lens. Until you have a completely opaque lens involving 100%, or completely opaque cataract involving 100% of the lens, and these horses should be referred to cataract surgery. Yes, we do cataract surgery in horses and we they can regain vision.

And We have arrived at the end of our atomical journey after looking at the lens, we want to examine the funders again at the risk of being repetitious. This is done in a darkened room with a dilated pupil to look at the funders of a horse. And determine whether it is normal looking or whether we have pathologies such as retinal detachment, this whitish curtain hanging in the back of the eye, whether there are signs of retinal atrophy, you can see the difference in colour.

Between the two optic nerve heads and the loss of retinal blood vessels and signs of retinal degeneration here or the classic butterfly lesions around the optic nerve in cases of chore retinitis. Now, there are several ophthalmoscopes that you can use in order to perform an ophthalmoscopic exam of the fundus. We can look using a direct ophthalmoscope and it's called direct because I'm looking directly at the funders of this leopard.

We can use them indirect and indirect. Legs and this monocular indirect is sort of compromise between the two. There are many advantages and disadvantages for each one, but really the two biggest ones are magnification and viewing field size as shows.

Here the direct ophthalmoscope gives you great magnification as you can see here, so you can see small lesions, but unfortunately the price you pay is a very small viewing field, meaning you need lots of time in order to examine all of the funders magnifications you may need small lesions, but it gives you. To a very large viewing field meaning you can see in 2 or 3 seconds and the monocular indirect is somewhere in between, but a nice cheap alternative for the fancy phthalmoscopes is take your transluminator stand at a fully extended arms away from. The horse, use a handheld lens here and you will get a pretty good view of the funders.

You can see that this is a recent picture because we're all with our COVID masks and I take the opportunity to wish you and yours best of health. Really, let me conclude with maybe this most important take home message about ophthalmoscopy. Please perform ophthalmoscopy with every horse that you see, not just every horse that comes for an ophthalmic exam, but every horse you see for the ophthalmoscopic exam is challenging.

It is complicated. You need time to master it and the way you Master it is you practise it on every horse just like you practise auscultation on every horse that you examine. I mean, we, we didn't know what the heck we were doing on hearing and we put on a stethoscope, but we didn't enough horses and we learned to recognise the normal lung and gut and heart sounds.

Same with ophthalmoscopy if you use an ophthalmoscope on every horse that comes in. To your clinic, then you will become a master and in this case I'd like, I'd like to quote Professor McCray. I think he was a Scottish practitioner in the 19th century, said more is missed by not looking than by not knowing.

It's OK not to know everything. That's why we have textbooks, but you really have to know how to look, which was the purpose of this lecture. This, by the way, is Dennis Brooks.

I mentioned him earlier, my mentor, one of my mentors from the University of Florida where I trained in veterinary ophthalmology. He's now retired, but really one of the founding fathers of equine veterinary ophthalmology, and I like to quote him by saying that horses really have just two ic diseases, corneal ulcers, and everything else. And therefore, I would like to invite you to join me in my webinar on November 9th when we will be talking about corneal ulcers and everything else, talking about common eye diseases in horses.

Thank you very much for your attention. I wish you a pleasant summer vacation and I'll see you again in November.