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Delan Jinapriya, MD, FRCSC, discusses the clinical examination for primary open-angle glaucoma.
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Delan Jinapriya, MD, FRCSC, discusses the clinical examination for primary open-angle glaucoma.
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Segment:0 .
>> Hello, and welcome to JAMAevidence, our monthly podcast focused on core issues in evidence-based medicine. I'm David Simel, the editor of Rational Clinical Examination Series and a professor of medicine at the Durham Veterans Affairs Medical in Duke University, in Durham, North Carolina. Today, we're discussing glaucoma. Joining me on the program is Dr. Delan Jinapriya from the Department of Ophthalmology, Queen's University in Kingston, Ontario. Hello, Delan, how are you doing today?
>> Very well, Dr. Simel. Thank you for having me. >> Let's start with some simple questions. Can you please define primary open-angle glaucoma for our listeners? >> Certainly. Primary open-angle glaucoma is one type of glaucoma where the angle of the eye, which is where the outflow system of the eye resides, is actually appearing to be normal but the pressure within the eye is elevated. >> Well, tell us about the prevalence, then, of glaucoma in the United States and Canada.
>> Certainly. You know, the prevalence actually depends on what race you're interested in. So, if we look at the Caucasian population, it ranges anywhere from about 1.2 to 2.1%, although if you look at some Australian and European population-based studies, the prevalence rates have actually been as high as 4%. Now if we look at black Americans, it has been found to be about 4.7% in a large, population-based study that was done in 1991 called the Baltimore Eye Survey. But other, larger population-based studies on black populations have actually found the prevalence rate to be as high as 8.8%. Now if you're looking at an Asian population and the best data we have, actually, groups together both East Asian and Southeast Asian ethnicities and, you know, we can debate as to whether this is an appropriate kind of grouping.
Nevertheless, the rate has been found to be about 2.5%, and I want you to bear in mind that the prevalence rates that I've just quoted are actually for open-angle glaucoma, and the overall glaucoma prevalence would actually include a closed-angle glaucoma, and you can add anywhere from 0.5 to 2.5%, depending on the race or the ethnicity that you're looking at. I also think it's important to note that these prevalence rates are based on data that we acquired in the 1980s and 1990s, and since then, our ability to diagnose glaucoma has improved, and we're able to diagnose it much earlier than we could a couple decades ago, and also, our population is actually aging, and that age is a risk factor in and of itself for glaucoma.
So, we would anticipate the prevalence rates of a more elderly population would also increase along with that aging population. >> So, you've mentioned a couple things that caught my interest. First off, you noted that glaucoma has to do with elevated intraocular pressures. Do all patients with glaucoma have elevated intraocular pressures? >> That's a very good question, and it's a really important point to bring up. The answer is no, and I want to stress this because 50% of patients with glaucoma do not have elevated intraocular pressures.
At one point, we used to tie the definition of glaucoma to pressure, and if you look at our definitions as they've stood for the last decade, we have eliminated pressure as a component of our definition for glaucoma. If you have elevated pressure, it certainly puts you at risk for glaucoma, but one does not need to have elevated pressure to have glaucoma. >> Well, this is starting to sound a little bit complicated. You also mentioned something about primary open-angle glaucoma and closed-angle.
What's the difference between those two types of glaucoma? >> So, the difference between these two types of glaucoma is primary open-angle glaucoma and closed-angle glaucoma is really anatomy driven. So, in an open-angle glaucoma variety of which primary open-angle glaucoma is one type, the drainage system is actually visible, and the challenge there would be in either the drainage system not working adequately in the case of high pressure, let's say. Or in some cases, the drainage system is open, and the pressure is normal, but we still are experiencing optic nerve damage.
Now in a closed-angle glaucoma variety, the drainage system is actually not accessible. And if you can imagine under those circumstances, the fluid, the aqueous humour, that's generated within the eye is going to actually stain the eye, and its exit is going to be impeded. As a consequence, we see elevations in intraocular pressure. This may be one that can be found in the clinic, because the pressure is always high, but perhaps, even more dangerous than that would be one where the pressure is intermittently high, and as a consequence, there are occasional spikes in intraocular pressure, resulting in nerve damage.
>> So, I guess the more common one is primary open-angle glaucoma, which is what generalist physicians would typically see. >> That is correct. Primary open-angle glaucoma has a higher prevalence rate than closed-angle glaucoma. >> Tell us about the risk factors, then, that have been useful in identifying patients who are at risk for primary open-angle glaucoma. >> The risk factors can be broken down into nonclinical exam dependent risk factors and clinical exam dependent risk factors.
So, in the nonclinical exam-dependent risk factors, you have family history, age, race, near-sightenedness, peripheral vascular disease, diabetes, and hypertension. And then, in the clinical exam dependent risk factors, you have nearsightenedness, increased cup-to-disc ratio, high intraocular pressure, disc hemorrhages, and cup-to-disc asymmetry. >> Are there generally accepted recommendations for the age when you should start screening for glaucoma?
>> There are some generally accepted recommendations and these are dependent, however, upon risk factors. So, without any risk factors, the only risk factor would be aging alone, and at that point, screening in one's 50s and 60s would be appropriate. However, if one has a family history or has a medical history that might otherwise predispose one to glaucoma such as, you know, diabetes, for example.
Then it would be prudent to start screening far earlier, perhaps, in one's 30s or 40s for glaucoma. >> So, to identify some of these examination features that you mentioned, a physician is going to need an ophthalmoscope, but I recognize that ophthalmologists have access to an indirect ophthalmoscope that generalist physicians don't have. The generalist physicians use a direct ophthalmoscope. So, someone who's never actually used an indirect, what would I see if I was an ophthalmologist that's different from what I see as a generalist physician?
>> Fundamentally, the difference lies in the ability to visualize the back of the eye with stereopsis as opposed to a two-dimensional view, which would be what a traditional, direct ophthalmoscope that a general physician would have access to. So, when you're using an indirect ophthalmoscope, and you're capturing an image at the back of the eye with stereopsis, the cup-to-disc ratio estimations will take into account where you see tissue and where you don't, and this is particularly challenging in that the retinal tissue and the nerve that we're looking at is actually translucent tissue.
So, the ability to see even subtle features such as shadowing and increased translucency, those all add to identifying where the true tissue structure lies. Without that, in a two-dimensional view, it becomes more monocular clues that we count on, such as color, and perhaps, the path of blood vessels. And in some cases, this can be quite misleading, especially color. If you're dealing with a pale disc, one might actually misconstrue that to be an increased cup-to-disc ratio, for example.
So, stereopsis provides an advantage in being able to identify where tissue is and isn't, a little bit more readily than would a direct ophthalmoscopic view. >> So, when I have my direct ophthalmoscope, and I'm looking at the disc in the fundus, what, exactly, should I be looking for to identify the patient at risk for glaucoma? >> You know, one is still looking to try and identify a cup-to-disc ratio, and one is also looking for what we call flame hemorrhages on the disc, or Drance hemorrhages on the disc.
The problem is that not everybody with glaucoma will have Drance hemorrhages, and also, the identification of the cup-to-disc ratio can be challenging; however, something else that one is looking for is an asymmetry between the right and the left eye, let's say. So, if there's an asymmetry in the cup-to-disc ratios, then that would also be something that would be concerning and would be, you know, a hallmark for increased risk for glaucoma. >> So, does asymmetry involve a difference in size, a difference in shape, or both of those?
>> It could be both of those. And so, the evaluation of asymmetry has to put into context whether the asymmetry is happening in nerves of similar size, in which case that would be more concerning, or whether the asymmetry is happening in nerves of differing sizes, in which one could for account for why there would be a cup-to-disc asymmetry. And the shape, also, likewise, you know, if there's a difference in the shape of your cup that would be a little bit more concerning because one might wonder whether one of the rims has thinned, and as a consequence, you're seeing a difference in shape of your cup.
>> So, are there ways to improve the detection rate of primary open glaucoma in the general population? >> Well, the glaucoma detection rate can be improved if there were more complete eye exams that were being performed. Now the extreme of this would say, well, we should be screening everyone with a complete eye exam, and while that may seem impractical, it would be much the same way as everyone at some point has seen a dentist, if not regularly sees a dentist, and the same should probably be true for one's eyes.
Somebody should see an eye care provider in some form, whether it's an optometrist or an ophthalmologist, for a full eye exam. If not, you know, at one point, on a regular basis. So, the clinical exam is one way that we identify glaucomatous damage, and in a generalist ophthalmologist office, it is the only tool that would be available with which to identify glaucoma, whereas we are now moving to a point where the new standard of care would be that we identify retinal nerve fiber layer damage before it is even clinically identifiable.
So, under these circumstances, it would be important to have patients who would have risk factors for glaucoma be identified and to, perhaps, be screened earlier with some of this other technology, in addition to the clinical exam, in order to put the full picture together and identify whether somebody is at risk or has glaucoma. >> Well, it sounds complicated, but it sounds like everyone needs an eye specialist at least once in their lives to detect glaucoma. Is there anything else you'd like to tell our listeners about the clinical examination for primary open-angle glaucoma?
>> Yeah, I think it's important to know that the clinical exam is a rather challenging one, even for those of us who focus on glaucoma as our subspecialty? And many times, it takes repeated examinations before a pattern becomes clear, and sometimes we're waiting for change to happen in order to truly make a diagnosis. So, I think it's important to note that diagnosis of glaucoma is easy when the disease is well-established.
However, the diagnosis is much more challenging if you're trying to catch the disease earlier in its stage, and that is actually our goal at this point is to try and catch it as early as possible, so that we can offset the amount of damage that happens and prolong the duration that people will have their vision for. >> Well, thank you, Dr. Jinapriya for talking to us today. More information about this topic is available in the Rational Clinical Examination series and on our website, JAMAEvidence.com, where you can find our entire roster of podcasts.
I'm David Simel, and I'll back with you soon for another edition of JAMAevidence. [ Music ]
Segment:0 .
>> Hello, and welcome to JAMAevidence, our monthly podcast focused on core issues in evidence-based medicine. I'm David Simel, the editor of Rational Clinical Examination Series and a professor of medicine at the Durham Veterans Affairs Medical in Duke University, in Durham, North Carolina. Today, we're discussing glaucoma. Joining me on the program is Dr. Delan Jinapriya from the Department of Ophthalmology, Queen's University in Kingston, Ontario. Hello, Delan, how are you doing today?
>> Very well, Dr. Simel. Thank you for having me. >> Let's start with some simple questions. Can you please define primary open-angle glaucoma for our listeners? >> Certainly. Primary open-angle glaucoma is one type of glaucoma where the angle of the eye, which is where the outflow system of the eye resides, is actually appearing to be normal but the pressure within the eye is elevated. >> Well, tell us about the prevalence, then, of glaucoma in the United States and Canada.
>> Certainly. You know, the prevalence actually depends on what race you're interested in. So, if we look at the Caucasian population, it ranges anywhere from about 1.2 to 2.1%, although if you look at some Australian and European population-based studies, the prevalence rates have actually been as high as 4%. Now if we look at black Americans, it has been found to be about 4.7% in a large, population-based study that was done in 1991 called the Baltimore Eye Survey. But other, larger population-based studies on black populations have actually found the prevalence rate to be as high as 8.8%. Now if you're looking at an Asian population and the best data we have, actually, groups together both East Asian and Southeast Asian ethnicities and, you know, we can debate as to whether this is an appropriate kind of grouping.
Nevertheless, the rate has been found to be about 2.5%, and I want you to bear in mind that the prevalence rates that I've just quoted are actually for open-angle glaucoma, and the overall glaucoma prevalence would actually include a closed-angle glaucoma, and you can add anywhere from 0.5 to 2.5%, depending on the race or the ethnicity that you're looking at. I also think it's important to note that these prevalence rates are based on data that we acquired in the 1980s and 1990s, and since then, our ability to diagnose glaucoma has improved, and we're able to diagnose it much earlier than we could a couple decades ago, and also, our population is actually aging, and that age is a risk factor in and of itself for glaucoma.
So, we would anticipate the prevalence rates of a more elderly population would also increase along with that aging population. >> So, you've mentioned a couple things that caught my interest. First off, you noted that glaucoma has to do with elevated intraocular pressures. Do all patients with glaucoma have elevated intraocular pressures? >> That's a very good question, and it's a really important point to bring up. The answer is no, and I want to stress this because 50% of patients with glaucoma do not have elevated intraocular pressures.
At one point, we used to tie the definition of glaucoma to pressure, and if you look at our definitions as they've stood for the last decade, we have eliminated pressure as a component of our definition for glaucoma. If you have elevated pressure, it certainly puts you at risk for glaucoma, but one does not need to have elevated pressure to have glaucoma. >> Well, this is starting to sound a little bit complicated. You also mentioned something about primary open-angle glaucoma and closed-angle.
What's the difference between those two types of glaucoma? >> So, the difference between these two types of glaucoma is primary open-angle glaucoma and closed-angle glaucoma is really anatomy driven. So, in an open-angle glaucoma variety of which primary open-angle glaucoma is one type, the drainage system is actually visible, and the challenge there would be in either the drainage system not working adequately in the case of high pressure, let's say. Or in some cases, the drainage system is open, and the pressure is normal, but we still are experiencing optic nerve damage.
Now in a closed-angle glaucoma variety, the drainage system is actually not accessible. And if you can imagine under those circumstances, the fluid, the aqueous humour, that's generated within the eye is going to actually stain the eye, and its exit is going to be impeded. As a consequence, we see elevations in intraocular pressure. This may be one that can be found in the clinic, because the pressure is always high, but perhaps, even more dangerous than that would be one where the pressure is intermittently high, and as a consequence, there are occasional spikes in intraocular pressure, resulting in nerve damage.
>> So, I guess the more common one is primary open-angle glaucoma, which is what generalist physicians would typically see. >> That is correct. Primary open-angle glaucoma has a higher prevalence rate than closed-angle glaucoma. >> Tell us about the risk factors, then, that have been useful in identifying patients who are at risk for primary open-angle glaucoma. >> The risk factors can be broken down into nonclinical exam dependent risk factors and clinical exam dependent risk factors.
So, in the nonclinical exam-dependent risk factors, you have family history, age, race, near-sightenedness, peripheral vascular disease, diabetes, and hypertension. And then, in the clinical exam dependent risk factors, you have nearsightenedness, increased cup-to-disc ratio, high intraocular pressure, disc hemorrhages, and cup-to-disc asymmetry. >> Are there generally accepted recommendations for the age when you should start screening for glaucoma?
>> There are some generally accepted recommendations and these are dependent, however, upon risk factors. So, without any risk factors, the only risk factor would be aging alone, and at that point, screening in one's 50s and 60s would be appropriate. However, if one has a family history or has a medical history that might otherwise predispose one to glaucoma such as, you know, diabetes, for example.
Then it would be prudent to start screening far earlier, perhaps, in one's 30s or 40s for glaucoma. >> So, to identify some of these examination features that you mentioned, a physician is going to need an ophthalmoscope, but I recognize that ophthalmologists have access to an indirect ophthalmoscope that generalist physicians don't have. The generalist physicians use a direct ophthalmoscope. So, someone who's never actually used an indirect, what would I see if I was an ophthalmologist that's different from what I see as a generalist physician?
>> Fundamentally, the difference lies in the ability to visualize the back of the eye with stereopsis as opposed to a two-dimensional view, which would be what a traditional, direct ophthalmoscope that a general physician would have access to. So, when you're using an indirect ophthalmoscope, and you're capturing an image at the back of the eye with stereopsis, the cup-to-disc ratio estimations will take into account where you see tissue and where you don't, and this is particularly challenging in that the retinal tissue and the nerve that we're looking at is actually translucent tissue.
So, the ability to see even subtle features such as shadowing and increased translucency, those all add to identifying where the true tissue structure lies. Without that, in a two-dimensional view, it becomes more monocular clues that we count on, such as color, and perhaps, the path of blood vessels. And in some cases, this can be quite misleading, especially color. If you're dealing with a pale disc, one might actually misconstrue that to be an increased cup-to-disc ratio, for example.
So, stereopsis provides an advantage in being able to identify where tissue is and isn't, a little bit more readily than would a direct ophthalmoscopic view. >> So, when I have my direct ophthalmoscope, and I'm looking at the disc in the fundus, what, exactly, should I be looking for to identify the patient at risk for glaucoma? >> You know, one is still looking to try and identify a cup-to-disc ratio, and one is also looking for what we call flame hemorrhages on the disc, or Drance hemorrhages on the disc.
The problem is that not everybody with glaucoma will have Drance hemorrhages, and also, the identification of the cup-to-disc ratio can be challenging; however, something else that one is looking for is an asymmetry between the right and the left eye, let's say. So, if there's an asymmetry in the cup-to-disc ratios, then that would also be something that would be concerning and would be, you know, a hallmark for increased risk for glaucoma. >> So, does asymmetry involve a difference in size, a difference in shape, or both of those?
>> It could be both of those. And so, the evaluation of asymmetry has to put into context whether the asymmetry is happening in nerves of similar size, in which case that would be more concerning, or whether the asymmetry is happening in nerves of differing sizes, in which one could for account for why there would be a cup-to-disc asymmetry. And the shape, also, likewise, you know, if there's a difference in the shape of your cup that would be a little bit more concerning because one might wonder whether one of the rims has thinned, and as a consequence, you're seeing a difference in shape of your cup.
>> So, are there ways to improve the detection rate of primary open glaucoma in the general population? >> Well, the glaucoma detection rate can be improved if there were more complete eye exams that were being performed. Now the extreme of this would say, well, we should be screening everyone with a complete eye exam, and while that may seem impractical, it would be much the same way as everyone at some point has seen a dentist, if not regularly sees a dentist, and the same should probably be true for one's eyes.
Somebody should see an eye care provider in some form, whether it's an optometrist or an ophthalmologist, for a full eye exam. If not, you know, at one point, on a regular basis. So, the clinical exam is one way that we identify glaucomatous damage, and in a generalist ophthalmologist office, it is the only tool that would be available with which to identify glaucoma, whereas we are now moving to a point where the new standard of care would be that we identify retinal nerve fiber layer damage before it is even clinically identifiable.
So, under these circumstances, it would be important to have patients who would have risk factors for glaucoma be identified and to, perhaps, be screened earlier with some of this other technology, in addition to the clinical exam, in order to put the full picture together and identify whether somebody is at risk or has glaucoma. >> Well, it sounds complicated, but it sounds like everyone needs an eye specialist at least once in their lives to detect glaucoma. Is there anything else you'd like to tell our listeners about the clinical examination for primary open-angle glaucoma?
>> Yeah, I think it's important to know that the clinical exam is a rather challenging one, even for those of us who focus on glaucoma as our subspecialty? And many times, it takes repeated examinations before a pattern becomes clear, and sometimes we're waiting for change to happen in order to truly make a diagnosis. So, I think it's important to note that diagnosis of glaucoma is easy when the disease is well-established.
However, the diagnosis is much more challenging if you're trying to catch the disease earlier in its stage, and that is actually our goal at this point is to try and catch it as early as possible, so that we can offset the amount of damage that happens and prolong the duration that people will have their vision for. >> Well, thank you, Dr. Jinapriya for talking to us today. More information about this topic is available in the Rational Clinical Examination series and on our website, JAMAEvidence.com, where you can find our entire roster of podcasts.
I'm David Simel, and I'll back with you soon for another edition of JAMAevidence. [ Music ]
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