Well, good morning, or it's good morning in California anyway, as, we welcome you to the, the 9th of the, webinar vets virtual conferences. They've been doing this long before the rest of us got used to doing them. So, welcome to the, ophthalmology section of, VC 2021.
And, it's my pleasure to, start off with what I think is really, hopefully a, a really nice topic, that I can make interesting for you and help you to realise the importance of the, the ophthalmic exam in reaching a diagnosis and therefore making the choosing the right therapies. It's my pleasure to be, working alongside an old buddy, Ron Offrey. Ron and Paul Miller and I have, known each other for, oh gosh, 20 or 30 years, I suppose, and have, jointly published, we took over Doug Slatter's book, and you can see Ron here in his, well, this is in Helsinki, I think.
And you can see that, Ron keeps the food right in front of him. So, Ron, nice to have you on the, ophthalmology stream here and, I know you'll, the rest of you will enjoy Ron's topics as well. Let's get started with the, the pearls of the ophthalmic exam.
And, and for those of you who are analogy learners, I'm a bit of an analogy learner. And so I'm a bit of an analogy teacher. And I hope that works for some of you.
You're gonna see the deer in the headlights and the headlights, in the fog and the standing at the face of the cave, and, and what a glass of water and its reflections can teach us about clear structures. And I'm gonna try and bring the, the ophthalmic exam, try to demystify parts of it for you. And I hope, I hope that works.
I hope that's a style that works for you. And what I wanted to start out with, though, was the top 10 tips. I'm gonna give you my top 10 tips.
Things that I've learned from lecturing around the world that people often ask, what's the best sedative, for instance? And I would say, tip number one, And these are in no particular order perhaps, but tip number one is to avoid sedation whenever possible. And when you do need sedation, choose the lowest dose possible of the minimal acting drug possible.
Remember, this is not a painful exam. All you need is for the patient to stay still. That's all you need.
So take everything you know about sedation. And take it to the absolute minimum. I would tell you that we sedate in a busy, 12, ophthalmologist practise at UC Davis, a busy 12 ophthalmologist practise, I would say that we sedate 3 to 4 patients per year.
For their exam. We have all sorts of other techniques like wrapping cats in, in blankets, like using minimal restraint in some dogs, like taking some dogs away from owners and leaving other dogs with owners. Having technicians who are just tremendous at, at calming, patients down.
Remember that sedation is going to affect almost every part of the eye exam. All of the neuro-ophthalmic testing, so PLRs, dazzle testing, menace response. All of your assessment of Shermat test, intraocular pressure, it's gonna make the eye become in ophthalmic and roll down and the third eyelid come up, you're gonna lose much of your eye exam.
I hope I've convinced you that do everything in your power, tip number one, to avoid sedation. If you must sedate, this is a just a wild animal, then use the minimum amount to keep them still, that's all you need. Get at eye level with your patient.
We'll use that as a, a point we'll expand on later on. But when you go to the eye doctor, you're at eye level with the patient, and there's a special reason for that. And so we'll explore that a little bit more in the next couple of slides.
We'll also explore this combination to do a really good eye exam. The top, hints number 3 and 4 are in combination to turn your room lights down and to take a bright light and some magnification. If a single misplaced eyelash.
Can blind a patient and lead to a nucleation. Then surely it's worth using some magnification. Think about that for a minute, one ectopic cilia.
Can cause an ulceration that gets infected, the eye ruptures, and that eye is blind and requires a nucleation. If one misplaced eyelash can cause loss of the organ of interest for ophthalmologists, then surely it's worth using some form of magnification to find that misplaced eyelash. And that's just a single example.
There are many, many times where magnification will make the diagnosis for you. And we'll talk about how to do that in a moment. Taking an orderly approach, you're used to that in your general physical exam.
My tip number 5 is to take an orderly approach. Back in the pre-pandemic days, we loved having, veterinarians visit us, for fellowships and, we even have a scholarship awards. And, Probably one of the most, frequent comments that they'll make is, that they left there with a sense of how to do the exam in a structured and orderly way every time such that they never missed something.
It's amazing really, something as simple as that. It's what they left the academic institution saying that's probably one of the most powerful things I learned, so I can't tell you how important that is. Not only should we get at eye level with the patient, but my top sixth tip for you is to bring the patient to the front of the table and to roll their head and their feet just over the edge, like they feel like they're about to jump down.
They will, as you lift the as you tilt the nose down, they will lift their eyes up. The exact opposite is what I think a lot of veterinarians do. The big dog is on the floor, they tilt the head up.
They tilt the dog's head up to look at it. As you tilt the head up, the eyes roll, the eyes roll down, sorry, as you tilt the head up, the eyes roll down, and the, you will miss the ventral third to one half of the globe. Maybe that's where the blood vessels were growing across the limbus and onto the cornea.
Maybe that's where there was something behind the third eyelid. Maybe that's where the hypopion had fallen into the ventral ante chamber or the high femur, the red cells or the white cells. Tilt the nose down so that the eye rolls up.
Tip number 6, absolutely critical, and all those areas of the eye that you've been missing in your exam when you examine the patient on the floor will be revealed to you. I've cheated a little bit with, tip number 7. Tip number 7's got multiple parts, but it's a, it's a tip named always.
There's a whole series of things that every patient should get. Every patient, and remember, always is in inverted commas. Whenever a biologist says, always, they're making something up, right?
I mean, always, you could always find an exception for me, and I, I get that. But here's some things to have in your mind as to, what's my excuse for not doing these? There's a way to ask it.
Why did I not retro-illuminate, check for aqueous flare, and measuring troical pressure? And those three are so important that they're actually going to form the majority of the, the seminar today. Couple of you are already thinking, Oh man, I'm gonna have to go out and buy a lot of equipment.
Really, what I'm gonna do is teach you to use the lights that are already hanging on your wall. The lights that are hanging on the wall of every veterinary clinic or that's sitting in the charger on the countertop. I'm just gonna have you use those, holding them in a different way, and learning what to interpret what you can see.
So we're not gonna have you buy a whole bunch of new equipment. We're just gonna have you use the equipment you've got at the moment to its full advantage. And although I think everybody does apply fluoresce stain, it shouldn't be the first thing you do.
And it shouldn't be binary. Ophthalmology, I think, I tended to, have a, a habit when I was in general practise. I, and, and I did.
I used to be a real vet. I really did used to be a real vet. And for about 5 years, all around the UK and Australia, and, it taught me a huge amount.
I still have amazing admiration for what veterinarians do. And I would tell you that being a specialist is way easier. I have it, I have it easier.
There's no doubt. So I admire what you're doing. But I had a tendency to think about staying as something that was the ophthalmic exam, and it was sort of binary.
Disease was either fluorocine positive eye disease or fluroine negative eye disease. And I knew about the steroids, and no steroids if they're fluroine positive, and steroids if they're fluroine negative. And, and I'd really encourage you to think about urine and in a, in a non-binary way, to think about it, as, as one another data point in the exam, and also to do it always, but to do it last.
Fursein's going to affect all the other parts of your exam. To give you an example, it's gonna make the Shermatier test absolutely irrelevant, so you'll see a patient with squinting. Ocular discharge, redness.
If the first thing you do is fluoresce, then you've missed the opportunity to diagnose dry eye in that patient with the three characteristic signs of dry eye, squinting, redness, and ocular discharge. So he, he needs fluorescent stain applied. For example, on this occasion after a Sherman tear test, also fluoresce affects your view of the eye.
So Do fluing every time, but always do it last. Here's another always, and that's always dilate the pupil if you think there might be lens, vitreous, or fundic abnormalities, retinal, choroidal, optic nerve. Now, it's OK.
Here again is always. Do you, do I always dilate the pupil? No, not always, but if I don't, I say that I didn't.
Because it's a bit like saying that you only examine the cranial abdomen. When you said abdomen palpates normally. If you say, I looks normal, and you didn't dilate the pupil.
You've examined one half of the eye. You've examined back to the pupil and no further. Now, the good news is that's where the majority of eye disease occurs.
So there's nothing wrong with not dilating the pupil. As long as you say, To yourself, to the medical record, and to the client. I only examined half of the eye today.
But I examined the half where most of the problems occur and I didn't see anything wrong. However, if that patient comes in with visual disturbance, And we didn't dilate the pupil. Then we cannot possibly say what's wrong with that patient.
Visual disturbance is most commonly a function of the lens or the retina. So, you've got to pick and choose when you dilate. I get that.
But remember, just think to yourself, to not dilate the pupil is to the ophthalmic exam, like palpating only the cranial half of the abdomen. It's OK to do it as long as you say out loud that you didn't complete the exam. Here's probably the one of the most important tips.
Always make an ideological diagnosis. At the end of the eye exam, it's OK to say there's conjunctivitis. That's exactly what you should aim for by the end of the eye exam.
What's not OK is to stop there, because there is no treatment for conjunctivitis. Well, there is. There's a treatment for every itis around the body, isn't there?
Give anti-itis drugs. So, treating conjunctivitis with an anti-inflammatory is going to control the inflammation. But is it gonna cause the cause?
Is it gonna control the cause of the inflammation? You see, let's just take some examples of conjunctivitis. Here's 4, actually it turns out that they're all cats, but that's not particularly essential to this example.
Or to this concept, it's essential to this example, it's not essential to this concept. Here's 4 cats that have conjunctivitis. No doubt about it.
Look at them. They have marked swelling of the conjunctiva, they have marked redness of the conjunctiva. Now the chlamydial conjunctivitis isn't so red.
But they have marked signs that at the end of the exam, I can say for certain that they have conjunctivitis. That is, they have inflammation of the conjunctiva. But then if you were to say to me, Well, what's the treatment for that, and you say, Well, I don't know, I give usually an antibiotic steroid combination for conjunctivitis.
Then let's look at these 3 cases and see what an antibiotic ster steroid combination would have done for foreign body conjunctivitis. Here's a grass horn behind the 3rd eyelid. The antibiotic will be helpful.
The steroid will potentiate any ulceration, and that is going to ulcerate that cornea. So not the best choice. Top right, herpetic conjunctivitis.
The antibiotic will, well, be helpful for secondary bacterial overgrowth. There's a flora on the conjuncti, it's overgrowing. Won't do anything for the herpes virus, and the steroids will.
Allow the herpes virus to flourish, same with the chlamydial, depending on which antibiotic you chose, may not even be effective against chlamydia, remember that's, it needs a highly specific antibiotic choice. And then allergic conjunctivitis, well, you could argue that the steroids would make excellent sense, and you're absolutely right. And the antibiotics probably wouldn't do any harm.
This cat was allergic to. The antibiotic that was being applied. So I just wanted you to think about, there's 4, where what we did, and here's what we made an ideologic diagnosis.
Here's the way I hope that I can help you to remember this. Always put a word in front of the diagnosis. There's no way to treat uveitis other than anti-uveitis drug.
There's a way to treat toxoplasma uveitis. There's a way to treat lens-induced uveitis. So always put a word in front of the diagnosis.
If you find yourself writing in your medical record or typing in your medical record conjunctivitis, then force yourself to put a word in front of it. Even if that word is idiopathic, it's OK, because then, an antibiotic will control the overgrowth and a steroid will make the inflammation reduced. But unless the cause goes away while they're on the antibiotic steroid, not because, then they won't get better or they'll get worse again when you take them off.
And point number 10, tip number 10, probably the most important of them. More is missed through, not looking than not knowing. And I, this is a, of course, a famous saying amongst physicians and veterinarians.
Of course, it's applied, of course, across all organ systems. But boy, never was it more true than for the eye exam. Because at the end of the eye exam, Even in an academic institution.
We very rarely run any tests. Yes, if we see uveitis, we may go looking for maybe suggest running a CBC or a biochemistry panel. Yes, if we see retinal detachment, we may recommend doing a blood pressure, a systemic blood pressure measurement.
I, I get all of that. But at the end of the eye exam for just about every ophthalmic diagnosis, blepharitis, keraitis, conjunctivitis, We're not going on and doing any further testing, so you can take this in one of two ways. You can say, well, I don't know, I'll, I'll just, I'll just try it, I'll just try a treatment and guess, or you can be totally empowered by this knowledge.
If you get good at the eye exam. Then you're good at ophthalmology. Because if you get good at the eye exam, you're good at making the diagnosis.
And you can always look up the therapy. Therapies change constantly, diagnoses change rarely, and the way we examine the eye hasn't changed since the 1600s. So, let's go into how we examine the eye and get that right.
If they were the top 10 hits, top 10 tips, then let let me now give you 4 of the requirements, 4 things you'd need to set up to do a good eye exam, and you'll you'll recognise some of these. They are also in the top 10 tips. When we go to the eye doctor.
We rest our little chin on the chin rest. The eye doctor gets that perfect alignment with our eyes. And then two things swing around us in arcs.
The eye doctor and his or her viewing angle swings around us in an arc, and his or her light source swings around in an independent arc, so that we can always illuminate and visualise from a different angle. But this means in our patients, get the patient up onto the exam table. By the way, that's the way to avoid sedation in a huge number of them.
Once they get up there, whether it be fear or not, they tend to just hunker down and that's your time to do your quick eye exam. Requirement requirements number 2 and 3 go together, and here's the first of our analogies. Here's the opening to the cave or the opening to the tunnel.
As I've thought about, why was it when I was a GP that I had so much trouble examining the eye, I've come up with really two things that just make the eye exam difficult. And I've spent my career as a teacher trying to work out how to make those more understandable and easier. One of the things is that the eye is composed of clear structures.
That is unlike almost anything else you ever examine anywhere else in the body. You're used to structures being coloured or textured. Or invisible.
Here we're talking about a structure like the cornea, the lens, the anterior chamber, the vitreous, the tear film, the majority of the eye. That is normal when you can't see it. How amazing is that when it comes and how challenging is that when it comes to you as the examiner.
As an examiner, I have to be good at. Not seeing something. I'm gonna give you a hint, a couple of hints for how to see clear structures.
The second thing that makes examining the eye difficult is that it is a series of narrowing apertures. The eyelids, or, in fact, let's go back a step, the orbit forms somewhat of a shading aperture. The next is the eyelids.
They form a completely obstructive aperture. Next is the corneoscleral limbus. So where the cornea and the sclero join, the limbus.
That's the next aperture. Then there's the pupil. There's the next aperture.
You've got this series of concentric, narrowing rings that each time are funnelling your vision more and more. It's like standing at the door of a cave, at the mouth of a cave. At the mouth of a tunnel.
Now if I was to take you to this bucolic looking cave here in the picture, and gave you a choice of flashlights, a choice of torches. And said to you, you can choose anyone you like. They range from the weakest on the left to the brightest on the right.
Then you'd say, and and if I said to you and I want you to look as far into the cave as you can, you'd say, OK, I'll take the brightest, most penetrating focal, magna light source I can. The next thing I'd say to you is, OK, and you can come back here to the cave mouth at either, midday, where there's bright sunlight, or you can come back at midnight when the ambient light is down. I want you to be able to examine the inside of the cave as far in as possible without entering it though.
Well, you'd come back at midnight. When you ruin, when you remove the ambient distraction, distracting light, you'll be able to see way further into that cave. We need to set up exactly that thing to see the cave of the eye, to see into the cave of the eye.
So take the dog to the darkest room in your clinic. Turn down or out the lights, and then take a bright light source and a, a bright light source and a source of magnification. Now, again, analysing what our physician colleagues do, they have a very bright light source and a source of magnification, all woven into one.
How can you get that? Well, there's at least 3 ways you can do that. Here on the outsides are a variety of loops, a pair of different types of loops, expensive loops on your left.
And cheap, 40 $50 US dollars for the Octivisor. You can get and use these in your practise. You must get and use these in your practise.
Get yourself some magnifying spectacles. Just get some +2s, and plus 3 spectacles from the pharmacy, from the drugstore, from the chemist. See, I'm bilingual.
And then for those of you who want to go the next step, these handheld slit lamps are what ophthalmologists use, and they are superb. There's now an SL 17, which is really remarkable. For those of you who love eye exams, this is a tremendous investment.
For those of you who don't love eye exams, $40 or $50 US dollars will get you a marvellous optivisor. And for those of you who already have a set of operating or dental loops, then they make a tremendous way to examine the eye. For those of you who don't want to spend a penny.
For those of you who say $40 is too much, but I want to do a good eye exam, then at least pick up the otoscope. Take off the cone and use the magnifying lens on that. You've got something in your practise already.
As I say, my goal is not to get you to go and buy a bunch of expensive equipment. My goal is to help you to do a great eye exam with what you have laying around the clinic already. The way to hold the lights differently.
Now there's one disadvantage from this method, the otoscope, as compared to all of these. All of these, we can take an independent light source, or in the case of the CAR slit lamp here, an integrated light source, but on the case of the loops, we can take an independent light source, and we can alter the viewing. And the illuminating angle, in other words, we can choose where our hand goes or where our head goes in relation to our hand, and therefore the angle of incidence and the angle of examination of the light.
With this one, the light source and the magnification are in alignment. That's the one downside of this method. OK, so we've got top 3 requirements.
A dim light, a dim ambient room. Bright light source and magnification. And our patient on the exam room table and us seated in front of them so that we're on eye level.
Nothing expensive, nothing complicated, yet revolutionise what you see in an eye exam. And the final thing is also, inexpensive as in free and just takes a a little focus, just takes you to pay attention. And that is to say I am, I'm going to always do my eye exam in the correct order and in an orderly, in a, a systematic and and a consistent order.
There are some things, when I say the correct order, that have to be done before another. You must do a Shermant test before you apply any eye drops to the eye. You should check the intraocular pressures before you dilate the pupil.
You must check the PLRs before you dilate the pupil. So there's a couple of if then steps. Other than that though, it's simply a matter of finding an order that gives you a good flow.
The same way as you already do your eye exam with a good flow, sorry, do your whole body, your whole systemic exam with a good flow. You might do nose to tail, then do your temperature, pulse and respiration. Or you may have a different way, but you do it in a logical checklist sort of a way.
And I'd recommend you do the same for your eye exam. The way that works well for us, and you'll see on these little pictures at the front, is to both start at the outside and work more and more and more centrally. So come in from lids, across conjunctiva, across limbus, across central cornea.
At the same time coming from in the bottom picture here, superficial to deep, solids to conjunctiva, to cornea, to ante chamber to iris, to pupil, to lens, to vitreous, fundus. So that's a good, Outer to inner and superficial to deep combination, but find one that works for you. All right, we've had 10 tips.
We've had 4 requirements, the way you need to set yourself up to do the exam. And now let's concentrate for the rest of the session on the 4 skills that we would love for you to develop. And notice that they're skills.
Only the last 1 may require you to get new equipment. Maybe you already have a method of measuring intraocular pressure in your practise. But the first three are just simply taking light sources you already have and learning a new skill, not a new piece of equipment.
But it's gonna say to you, hold that light differently and interpret the way, interpret what you see in this way. So hold on, here we go. First one of the four is retro illumination.
The name is perfect. Think about retro illumination. The other way that we would say this in lay language is something was backlit.
It was lighted from behind. It was backlit. It was retro illuminated.
The way we do that, The way you backlight the eye, you can't get a light source into their brain and shine it out along their optic nerve, although that'd be cool. We can do it simply because of the reflective tapedum in the back of the eye. We now light to hit the tapedium and come back to us.
It's that deer in the headlights look, or that wild animal in the headlights look. And to get that view, and by the way, a lot of people will say to me, what about if this unusual dog or unusual cat doesn't have it to feed them. Well, none of us, you and I, humans, none of us have a topium.
And yet, we get a reflexive, a, a, not, not neurologic reflex, a reflective, light, you know, that red eye that you'll see in somebody's photograph. That's off that choroid. So you don't have to have a topedum for this to work.
It'll happen off the back structures of the eye. If you set yourself, the room, the patient up, you know, just the way I'm gonna tell you. We've got to do exactly what we did to get this view of the deer in the headlights.
In other words, we've got to be at a distance from a patient. We've got to be in alignment with the lights. So the headlights of the car and us as a passenger, gotta think about that set up at a distance in a very dark night.
So you've got to see them at night, you've got to see them at a distance, and you've got to be a passenger or the driver of the car. Well, here's how we do that. We set ourselves up in our exam room by turning out the room lights, by getting the light source right up alongside our eye, and standing back at a full distance, at a full arm's length distance from the patient.
And here you can see that not only are we, that we're not exactly on eye level with our patient. Here we've got the patient standing on the table, and we're just a little lower than they are, because remember, the tapedum is in the dorsal half of the eye. Now, in cats that have a huge tapedium, you can be at eye level with them.
But in small dogs in particular, they'll have a small topedium. The general rule is small dogs, small topeded them. Big dog, big to feed them, and cats, huge to feed them.
For a small dog in particular. They're the hardest to get down lower on, you'll need to get down lower and look up. Into the dorsal half of their eye, from arm's length with the light source held onto your temple, so that as you move around to get yourself better aligned, the light source moves with you.
You don't have to think about it. Here's the view you'll get. You get that reflective view coming back off on this occasion, a green topium.
And you can see that if you do this from a distance at first, and that's the important part, stand back at a distance, then two things will happen if you're at a distance. One is that the pupils will be more dilated than if you're up close. They won't be really widely dilated, but they'll be more dilated.
And the more dilated the pupils are, the more of the eye gets backlit, retro eliminated. The second reason to stand back from a distance is that the lights, and if you aim the light right over the bridge of the nose, then the eyes, the light splays out and equally illuminates both pupils. This is where retro illumination has its advantages.
Retro elimination does 2 things for you. Do you remember that business I said about an eye exam being difficult cause you have to find structures as and assess them as normal, if you can't see them. That assessment of clear structures as normal.
Retro illumination is one of the two techniques I'm gonna give you that are brilliant at assessing the clarity of the structure. The light has passed through all of the clear ocular media twice through the tear film, cornea, aqueous, lens, vitreous. Hit the taped and come back through the vitreous lens, aqueous, cornea, tear film, and come to you.
You have doubled your chances of seeing any irregularity, any opacity in any of those clear structures of the eye. The vast majority of the eye, you've got about 99% of the eye examined. If you examine only the clear structures.
The only thing you haven't examined yet is the eyelids, the conjunctiva, the sclera, the iris, and the tapedum, and the choroid and the retina. So you've examined the vast majority of things that have problems with them, cornea, tear film, anterior uvea, antechamber, lens. Think about all the diseases that you see in ophthalmology that you will have detected if you examine just the clear structures.
The second thing If retro illumination's best advantage is that it allows you to assess clear structures that are otherwise difficult to examine. The second thing that's brilliant about retro illumination is its ability to detect anisocoria. Now a couple of you are thinking, I see so few neuro-ophthalmic cases.
I'm not talking about neuro-ophthalmology, although it's helpful for that as well. I'm talking about conjunctivitis. Glaucoma and uveitis, the top 3 diseases that cause redness of the eye.
3 diseases with a different diagnosis, treatment, and prognosis. If I treat the glaucoma as if it has conjunctivitis, he will go blind. If I take the conjunctivitis as if he has glaucoma, his conjunctivitis could well get worse because many of the glaucoma drugs are irritating and they're certainly not helpful for conjunctivitis.
Differentiating the top three causes of red eye disease is best done, or at least I should say, can be really facilitated, that's a better way of saying it, by retro illumination. Let me explain why. We're gonna go looking for Anna Sequoria.
It turns out that when you go to examine an eye up close, You will create. And I sequoia, don't know whether you know that, the pupil that is directly illuminated will become smaller than the one that is indirectly, non-directly illuminated. So when you examine an eye up close and look at that one, then look at this one.
Not only are the pupils moving, which makes it difficult, you're actually creating anti-souria when it didn't exist or if subtle anti-souria pre-existed, you will ablate it with your eye exam. So assessing satelano sequoia is really important and retro illumination, arm's length from the patient, light on your temple. Light equally over the bridge of the nose, illuminating both pupils will differentiate for you on many occasions, the top three causes of red eye.
Here's a patient who has a reddened eye, OK, this is a cat, and we can see that he's got some obvious deep, big wriggly vessels here and a general red blush over this conjunctable surface. His bulbar conjunctiva overlying the sclera is red. He might have conjunctivitis, he might have uveatis, he might have glaucoma, they all require completely different approaches.
Here is that same patient, by the way, this was his right eye. Here is that same patient. Now this patient didn't have subtle anisocoria, but I'm using him as an example.
And notice that as we retro eliminate him, actually this pupil on the left is sufficiently small that we couldn't even get a view of his tapedum in this view. Had we dropped down a little lower, we would have. And notice now that instead of just assessing the one eye, we're now assessing in bi retro elimination from a distance, we're detecting subtle anisocoria.
Oh sorry, on this occasion not so subtle. What does that mean? What does anisocoria in the unilateral red-eyed patient mean?
Well, I can tell you absolutely for certain that there is no way this cat has conjunctivitis. It just is impossible. The flimsy little conjunctiver on the surface of the eye never makes the inside of the eye unwell.
The inside of the eye can make the flimsy little conjunctiva as an innocent bystander unwell, but the reverse is never true. So if there's intraocular changes, pupil on this occasion, it can't be due to the conjunctiva. The conjunctival inflammation has got to be due to the intraocular changes.
So, if I was to send this patient home with an antiviral treatment for his herpes, for an anti-chlamydial treatment, thinking it was chlamydia, with with antibiotic and a steroid mix cos it's just conjunctivitis, he would either go blind from his acute glaucoma if that was my misdiagnosis. Or he would go blind and or die from the cause of his uveitis. You see how critical diagnosing these three is, and you see how easy it is.
I've just absolutely eliminated. While this may be conjunctivitis, this absolutely cannot be. And better still, it is probably glaucoma, because a red eye that's midriatic is typically glaucomatous, and a red eye that's meiotic is typically uvetic.
So you notice what I said there typically is important or often as written in this slide. Whereas conjunctivitis is never produces anisocoria, anterior uveitis typically produces meiosis, and glaucoma typically produces medrisis. That's the first reason that we do retro illumination is to look for an isocoria.
If it's in a unilateral red-eyed patient, then you are well on the way to diagnosing which of the top three diseases it is. There's another reason to do it though, and that's to examine those clear ocular structures, the tear film, the cornea, the anterior chamber, aqueous humour, the lens, and the vires. And to do that, you want to get a bit closer.
You want to be examining what is that linear structure that's that's opaque and obstructing the retro-illuminated view. And if you come in close, the pupil's gonna get smaller. So I do recommend that if you do also do retro illumination after dilating the patient.
I recommend trapiamide. Trapeamide is the, is the drug name, not the brand name. Moryao is probably the most common brand name.
Trapiamide is a short acting, Fast acting, weak acting, equivalent of atropine. So it's going to only dilate them for hours instead of days. And it's too weak to overcome the spasm of uveitis.
But it's great for diagnostic use. So it's great for dilating normal pupils. To examine the rest of the eye, or to use the fundus to examine the rest of the eye, and that's what we're doing in retro illumination.
You dilate them and then view them up close. And this is where We say it's really difficult to assess a clear structure, but retro illumination is your answer. It's really difficult to assess a glass of water.
But if you put something behind the glass of water, then you get a feel for how clear that glass of water is by how well you can examine the thing behind it. Turbid fluid in the glass, obstructs your view of what's behind it. Let's look at that.
Here's a turbid fluid in the glass. Something is cloudy in this eye. Let me get you oriented.
This is a dog. This is his left eye, so this is the medial canthus here with the third eyelid tucked way down in here. Here's the corneal, here's the sclera.
Here's the corneal scleral limbus, and here's the pupil, which we have pharmacologically dilated. There are a lot of little silvery reflections up the top here, ignore those, but notice the central opacity. Now with a photo, you lose depth perception, but let me tell you that that was within the lens.
So there is a nuclear opacity, a nucle the nucleus of the lens is opaque. This is either a cataract. Which means he might have diabetes, might have an inherited disease that we shouldn't breed him for, may have uveitis as a result or a cause of his cataract.
In other words, a disease that has all sorts of implications in management and diagnosis and treatment and advice to the client. Or he may have nucleosclerosis, that hardening of old age compaction. That's a factor of having spent 8 to 10 years of dog years on this world, on this globe.
And there's no impact on vision that's meaningful. They can't read the paper anymore. There's no, they need these glasses, like I'm wearing.
There's no impact to their health. There's nothing that needs to be done. See the difference?
Retroination is what's going to differentiate nucleosclerosis, the ageing change from nuclear cataract, the change that has all sorts of implications. Here's that patient examined, he's got a central nuclear opacity, take my word for it, it's in the lens. In a photo, you can't get depth perception.
And here is that same patient, retro illuminated. We stood back at a distance, we dilated the pupil, and we got a great glow back from only a tiny percentage of the fundus. This bright yellow around the periphery is the colour we expected from his fundus.
The, you can see that centrally, it's completely, or perhaps variably opaque. Obstructed and that there are little spokes and rims of obstruction out into the peripheral, that we couldn't see here, so it's told us two things, retro illumination has told us this is something that is obstructing light. That's a cataract, by the way.
And, boy, there's more to it than we thought in this. There's other areas that are more subtle out in the periphery here. This ring, for instance, and these spokes, and these smudgy little circles, like down here, out here, and out here.
This was a nuclear cataract. By contrast, here's another eye, and again, ignore this and this. These two are reflections of the thumb and the hand of the holder.
But here again is a left eye of a dilated pupil, and you can see that there is a smoky central. Again, you'll have to take my word for it that it's lens. It's not the The ocular surface.
And here is a smoky blue eye. When we retro illuminate this one, notice there's a little, there's our pupil out there, and there's a little ring in the centre of the pupil. It's not obstructing the light, but it's bending the light.
This is nucleosclerosis. So I hope I've convinced you that retro illumination is a phenomenally important thing to do. If you do it from a distance prior to dilation, you'll detect anisocoria.
Anisocoria is helpful with neurologic disease, sure, but that's not so common. It's important for different. Top 3 causes of red-eye.
If you do it up close after dilation, when the people won't constrict as you get up close, then you will have been able to visualise twice, like goes through them twice and come come through once and comes back, all of the clear ocular media. All right, sip of coffee? While you gather your thoughts about retro illumination.
And now we're moving to something totally different, but using the same light source, and using our same eyes. Here, we're going to do everything with focal illumination, or sometimes called trans illumination. And in fact, I like trans illumination, because trans means from the side, right?
So if retro illumination was backlit, then trans-illumination is side lit. It's everything that retro illumination was not. Retro elimination, at least in the first half, was at a distance.
This is up close. Retro elimination was you and the light source in alignment. This by definition, is saying, let's vary those illuminating and viewing angles.
Let's do, shown in the bottom left here, what the physician would do if we went to the eye doctor. Let's swing the lights and the examiner around us in two independent arcs. If you go and buy one of these fancy slit lamps, then this front light source here hinges in an arc.
If you go and buy one of these $40 magnifying loops, then you can move yourself in whatever position you like, and you can independently move your light source in whatever position you like. You will be, just practise this, just try it. Just, just play with it.
Next compliant patient you have, your own dog at home. Just try it. Room lights out, shine the light from the side and examine from the front.
Then shine the light from the front and examine from the side, and you tell me the difference that you can see there. It is striking the difference you'll get. All the perspective, all the shadows, all the depth perception, all the reflections, everything changes, and you will make diagnoses that you would have completely missed.
All you have to do is move, it's amazing. And I would say this is the thing that our students have the most trouble with. Our students come and rotate through on OO for 2 weeks with us.
And on the first day, on the first exam, they're examining like this. And they've got the light source and they're frigid, and the dog's frozen, and they're just staring at it and they're going, I think I can see, I think, I think I can see by day 3, they're moving around, they're swinging the light in from different angles, they're looking from above and below. They're going, this is incredibly cool.
I think I can see the anterior chamber. I've now got some depth perception. This opacity's definitely in the lens.
It's behind the pupil. And you just have to get freed up and moving around that patient. You will love it.
And as you're doing so, let's use our second glass of water analogy. The only other way you know that there's something in the water, there's something in the glass, there's some opacity, or that it's clear. The only way you do that is not just by looking through it, which is what we did in retro elimination, but by watching.
It. Watching its reflections. It's all about learning to see reflections again.
I mean that. You know, when you are growing up, you are captivated by reflections. You see the babies staring at themselves in the mirror, right?
Reflections catch our eye. They literally catch our eye. Now we have to learn, oh, by the way, then we stop seeing the reflections.
I don't see the reflections on these spectacles. You see the reflected light of them. If I saw that all the time, it would be constantly, but I notice it.
I, I don't see it, but I somehow notice it. So when I approached the glass door, I know to put out my hand and open it. I caught a reflection, but I didn't notice the reflection.
I caught a reflection. We need to start to notice the reflections again as ophthalmologists. Here's the reflection of the cornea, it tells us how smooth the corneal surface is, it tells us how good the tear film is.
Here where the lid meets the cornea is the lacrimal lake. Here's a bigger one down ventrally. There's even one out laterally.
This cat has a fantastic tear film. Here's the razor sharp eyelid margin. It's concentric with the pupil.
There's no entropyon. I can see the margin all the way around. And for those of you who look up close, here's the mybomian gland orhyy.
See each of those little dots? It's just amazing what you can see with reflections and reflections teach you a huge amount as well about abnormalities. Look at the differences here.
Yes, I can see it's been fluoresce stained. Yes, I can see there's blood vessels, but let me pause for a moment and look at the reflections. Look at all these reflections across the corneal surface.
This is a, not just ulcerated as shown by the fluorocene, but there are areas that are raised as well. This is in the irregular corneal surface. Where the lacrimal lake should be, maybe there's a little one there down ventrally.
Maybe there's a little one up there dorsally. But where the lacrimal lake should be, there's some fluffy conjunctiva come popping out and stop the lacrimo Lake. And compare the razor-like margin on this photo.
Beautiful, sharp, unbroken line with dots of mybomian glands. Compare that with this big, thick, irregular, broken line with virtually no mybomian glands, maybe two there. Swollen lid, choked up my bomian glands, all brought to you by the power of reflection.
So learn to look at the reflections. It's the best way I know to examine the clear structures of the eye. By the way, there are also reflections deeper in the eye of the lens.
All the clear structures reflect. Well, if the first two took your light source and just had you hold it in a different angle, the third one is a 3rd way of doing that. It's just taking those same old light sources that you always have hanging on your wall and wondered what to do with.
And now we're gonna tell you how to handle them so that they give you a brand new finding. And finding number 3, or skill number 3 is the assessment of aqueous flair. An aqueous flair.
Is an outstanding finding because it is pathoaemonic for uveitis. It is stuff floating in the tear film. So I'm sorry, not the tear film.
It is stuff floating in the anterior chamber, the aqueous humour, it's turbidity, it's cloudiness, it's like fog in the normally clear air. That's the analogy here. So we're gonna take something like the headlight of a car, the fog light of a car, an incredibly intense beam of light.
And notice that we're gonna view it from an angle. We're gonna watch the beam as it passes through the fog. And to do so, we're gonna get up very close.
So we're going to take this direct ophthalmoscope that you're used to using to examine the retina. Turn the wheel that spins horizontally on the front here, and turn it to the smallest circle possible. It doesn't matter what this vertical wheel here is set to.
Take this one, spin it horizontally to the smaller circle, and bring it in frighteningly close to the eye. See how close we are here? And then as the light traverses.
The ice chambers, view it from the angle that this photo was taken. So you've got about a 45 degree angle between your light source and your eye. And you're gonna watch it as it traverses the anterior chamber.
Here's a mockup of what that would look like. You would normally, in the normal patient, see a little slit of light on the cornea and a big beam of light through the through the lens. But the anterior chamber would be free of light, because there's no protein, there's no flocculent material in a normal anterior chamber.
When you get oozing from the iris, anterior uveitis, oozing from the iris into the anterior chamber, the material in the anterior chamber becomes floculent, cloudy, and you'll see the beam of light going all the way through. In each of these photos, the white arrow, the entire arrow in both of these photos is at the corneal reflection. The white arrow head is at the lens capsule reflection.
And in the top left, you can see that there is no beam of light visible between the two, between the arrow on the cornea and the arrowhead on the lens capsule. Notice the bracket, the parenthesis sign here. The bracket symbol is showing cloudy anterior chamber, pathonemonic for uveitis.
All you do, turn the room lights out. Notice this photos taken in the dark. Take your direct ophthalmoscope, turn it to the smallest circle.
Bring it as close to the cornea as possible. And examine the eye at an angle as the light passes through the chamber of the eye, using some magnification. Look for smoke in the anterior chamber, look for fog in the headlights.
If you see fog in the headlights, if you see smoke in the anterior chamber, then you have diagnosed uveitis. Now remember rule number 9, always put a word in front of. There is no treatment for uveitis other than steroids.
Or nonsteroidals. There is a treatment for toxoplasm or uveitis, cryptococcal uveitis, leptospira. Uveitis.
Always put a word in front of. The UVitis, so you still, this is one of the patients who does need diagnostic testing. But you're finished with your eye exam, you've discovered a sign that can only mean UBAs.
Quick take home on this one before we do our our last test. All patients with flare have uveitis. But not all patients with UVIis have flare.
So think of it as having a 100% positive predictive value, but a very low negative predictive value. Well, as promised, here's the last of our four skills, and I hope that these have been useful to you. And this is the one that may require you to purchase something, unless you already have one of these instruments, or maybe you have the old Shiotstenometer in your practise.
By the way, a highly, reliable tometer in the right hands. It's just that it's more difficult to use, needs a conversion table, it's just so clunky. These new varieties, the couple of toopen varieties and the couple of tonne of vet varieties are inexpensive when you charge for them and use them in appropriate patients.
They diagnose not just glaucoma. For those of you who say, I never got one of those, you know, they were like $4000 US dollars, and, and I don't see many glaucoma patients. You've missed the point.
These these diagnose glaucoma where the pressure is high. Uveitis, where the pressure is low. And conjunctivitis, where the pressure is normal.
See how you can use this to diagnose conjunctivitis. The patient with a reddened eye might have uveitis, might have glaucoma, might have conjunctivitis. The pressures in all three are different from each other.
It's amazing. What are some other signs of UVA glaucoma? Well, a cloudy eye.
An eye with an altered pupil, meiosis for uveitis, midriasis for glaucoma, and I with visual disturbance. And I, that's painful. So in other words, any eye that might have any of those signs should have the pressure taken because it might have uveitis, conjunctivitis, glaucoma.
So wait a minute, any eye that is red. Blue, cloudy. Has an altered pupil, has altered vision, is painful, has discharge.
Wait a minute, all of these are eyes that could have UVAS, conjunctivitis, or glaucoma? Absolutely. So all of them need the pressure taken.
Wait a minute, that's every I you see. Every eye you see needs its pressure taken. That's why it's not just for glaucoma and that's why this instrument pays for itself.
These are about 2.5 $3000 US dollars, roughly. People charge over here $25 a time.
100 pressure measurements, it's not 100 patients, because guess what you're gonna recheck in the glaucoma patient, the conjunctivitis patient, the uveitis patient. You're gonna recheck pressures on every one of them. So 100 measurements, that's not 100 patients, 100 measurements, let's say 50 patients checked twice.
It'll be less than that. The instrument's paid for itself already. Not to mention the recheck examinations, the drugs, not to mention the fact that you've done a good job.
Normal pressures, about 10 to 20 millimetres of mercury. That's a big variation, right? If a normal dog could be 10 or 20, or anything in between, but notice that you shouldn't have great variation between eyes.
So if a dog comes in with a pressure of 10 in the right and 20 in the left, And if the right eye is red, And his pressures are low in the red right eye with 10. And that's UVotti. If he comes in with 10 in the right and 20 on the left, and the left eye is red, then that eye is 20 with a red eye.
In a, in a patient who apparently is normal is 10, that's double normal. That's that warrants investigation for glaucoma. Remember though, it is just a test result.
And what I just said was, if you diagnose a pressure of 20, you've diagnosed a pressure of 20. You haven't diagnosed glaucoma yet. You've got to go looking for the signs of glaucoma.
Does he have madriasis? Does he have a cloudy pupil? Does he have reduced vision?
Does he have a small optic nerve head? Think about it as blood glucose. You measure the blood glucose, if it comes back high, you don't start him on insulin.
You say, gee, I wonder if you could have diabetes. I'll go looking for other consistent signs or I'll recheck that blood glucose at a fasting sample down the line or I'll do a urine glucose. You do confirmatory steps, tests, exams, rechecks.
We should do the same for pressures. We don't treat pressure, we treat disease and pressure's one of the ways we diagnose disease. That's all I had for you today, except to mention an old colleague, an old friend, a Manchester ophthalmologist.
I know that Anthony, from Webinar Vett was, a, a good friend of PIP's, and, we're, Ron and I, at, with Anthony's, help and compliance of, dedicated, these sessions to PIP. I hope you've found this useful. I'm really looking forward to seeing you for our other topic, feline herpes virus.
And I hope that the, how to examine and, with the instruments you already have hanging on the wall was useful to you. Thanks so much, and we'll see you for another seminar sometime. Bye for now.