 So for today's webinar again title is vision, eye disease and the onset of problems the CLSA presented by Dr. Ellen Freeman. She's an associate professor in the School of Epidemiology and Public Health at the University of Ottawa. She's also a scientist at the Ottawa Hospital Research Institute. She received her PhD in Epidemiology from the Johns Hopkins Bloomberg School of Public Health. Her research interests focus on better understanding the causes and consequences of visual impairment and eye disease. Now I will pass it along to the presenter. Thank you Jennifer for that introduction. I'll just share my screen here. All right, good afternoon everyone. It's a pleasure to be with you here today. And so, let's get started. So, before we get started with this particular project, I just wanted to go over some of my research program themes. So I am an epidemiologist, and my research program focuses on the epidemiology of visual impairment and eye disease. The themes that I have within my research program include determining the frequency of visual impairment and eye disease so both here in Canada as well as around the world, understanding the risk factors for visual impairment and eye disease, examining the impact of eye disease on things like mobility and mental and physical health, especially in older adults, and developing and testing interventions to try to reduce the impact of eye disease in those populations. And so I just want to start out by going over some background on vision and eye disease. So let's talk first about what is visual function. So what does it mean to see well. So there are different measures of visual function and most of you are probably familiar with visual acuity. And visual acuity measures how well you see fine details. So visual acuity is typically measured using a white chart with dark black letters that get progressively smaller as you go down the chart. However, much of our world actually exists at lower levels of contrast. And so contrast sensitivity is another measure of visual function that measures how well people see at lower levels of contrast. And it's measured using a white chart with letters that get lighter as you go down the chart but stay at the same size. So visual field is a measure of how widely you can see when you focus on one point. So if you're staring straight ahead. Can you see what's going on out here, and up here and down here. So all of those are static measures of visual function because you're staring at something that does not move. There are other measures of visual function that are dynamic. So maybe you're asked to identify something that's moving or not and which direction it's moving. And so motion detection is a type of visual function, which can be measured by viewing a group of dots and on the screen and indicating which direction are they moving. And with each successive trial, the movement of the dots gets more and more small. And so it's difficult to detect. So let's talk about visual impairment. So when we talk about visual impairment, we're often talking about visual acuity that's below a certain cutoff. And so in countries like Canada and the United States and Australia we typically define visual impairment for research purposes as visual acuity worse than 2040 vision. Now the World Health Organization does use a different cutoff that's a bit more severe so they use worse than 2060. And so how big of a problem is visual impairment in Canada. So using CLSA data, my team and I a few years ago published this paper. And we found that 5.7% of people in the CLSA had visual impairment using that 2040 cutoff. And as you can see here in the figure, it varied quite a bit by age so in middle aged people visual impairment is not that common it's about 3%. But as you get into your 60s 70s and 80s, it becomes much more common so in the oldest age group about 16% of people had visual impairment. Now, so the CLSA is done in community dwelling adults but what about the situation in nursing homes so these data come from the United States, but I suspect that the situation is similar here in Canada. So these data come from a sample of about 30 nursing homes in the state of Maryland. And this is what they found so the gray bars indicate visual impairment and the black bars indicate the prevalence of blindness and so you can see that when you get into older age groups and nursing homes, the majority of people have some visual impairment. And this fits with a paper that I worked on with Ellen Keguat and Mary Jean Keguat in Quebec a few years ago, where they sent surveys to long term care homes throughout Quebec, and they found that for the majority of homes, you had to request eye care. And you had to actually leave the home to get that eye care and so you know that's not ideal ideally you'd have people going into assess people's vision. You'd have eye care professionals going into the homes on a regular basis, in order to reduce some of this burden. Now, within the community, believe it or not the leading cause of visual impairment is actually uncorrected refractive error so that means near-sightedness, far-sightedness, astigmatism, presbyopia, things that can be corrected just with glasses or contact lenses. And so we see this in study after study around the world and community dwelling adults that the leading cause of visual impairment is refractive error. So something that can easily be treated. So other major causes of visual impairment are shown here on this slide. So cataract is shown in pink and it's responsible. It's a major cause of visual impairment as well. And then the other causes of visual impairment do vary a little bit depending on the race or ethnic background of the person. So age-related macular degeneration is shown in blue, glaucoma in yellow and diabetic retinopathy in gray. And so I just want to talk a little bit about some of those causes of visual impairment because I'm going to discuss them later in my analysis. So age-related macular degeneration, which I'm going to call AMD now for short. It is a disease that destroys your central vision. So if you were to look at the photo of the two boys there and you had fairly severe AMD, you would have a hole right where you're fixating. And AMD is typically a bilateral disease. There are two types of AMD. There's wet and there's dry AMD, but both types in their advanced stages cause central vision loss. Now, luckily, there are some treatments available for wet AMD. And so I meant, I meant to say age-related macular degeneration affects the macula, which is part of the retina in the back of the eye. And so another leading cause of visual impairment is glaucoma. Now, this disease will start at the periphery so out here. And so you might not even notice it until it gets rather severe. And so in its more severe stages, it's almost like looking through a tunnel. And this disease is also typically bilateral because it starts in the peripheral vision, unless you get regular eye care, you may not know you have it. So a lot of people are undiagnosed with glaucoma. And there's different types of glaucoma here in Canada. Primary open angle glaucoma is the most common type. You may have treatments that involve lowering the eye pressure of the eye either through eye drops or laser or surgery. And finally, cataract is when the lens in your eye becomes cloudy and that leads to blurry or hazy or less colorful vision like shown in the picture here. And luckily we have cataract surgery, which is an excellent surgery that can remove the clouded lens and replace it with an artificial lens. And a bonus of having cataract surgery is that the surgeon can tailor the lens to be to make it so that you may not need glasses after you have surgery. All right, so now I'd like to give a little bit of background on mobility. Why am I interested in mobility? Well, research shows that mobility loss in older adults may be a preclinical stage of disability. And so I just want to point out this study published in the Journal of the American Medical Association by Newman, and they had people who said that they didn't have any mobility problems. They had them walk 400 meters. So that's once around an outdoor track. And those people who scored in the worst quartile of time to walk that 400 meters. They over the next five years had an increased risk of death, cardiovascular disease, mobility limitations, and disability. And so, you know, as an older person, mobility loss could indicate the beginning stages of disability. So think about that in terms of a conceptual framework for that this project could fit within. So once someone loses their vision, particularly at an older age and develops mobility problems that can cause all kinds of other adverse health effects. If you start to stop leaving your neighborhood, stop leaving your house because you can't drive in your, you feel less confident walking around outside of your, your general area around your house. Your life is may become less cognitively interesting, you may become socially isolated, you may get less exercise, and all those things could lead to health problems, obesity, depression, cardiovascular disease. So it could either cause those things or exacerbate those things. And of course that can put you in a state of disability or nursing home admission or premature mortality. So if we can intervene, if we can understand these pathways and intervene and try to prevent the mobility problems, maybe we can prevent all these things that might stem from mobility problems as well. So how do we go about assessing mobility? So there's no gold standard test. The right test for your research will depend on your research question and on who's in your sample. And so if you have a sample of people who are hospitalized and they're frail, you know, you're going to use a different test than if you have community dwelling middle aged people. And so it's important to keep that in mind that the right test is going to depend on your question and your sample. When you think about what kinds of things does a person need to do to have full unassisted mobility. So I mean, mobility without the help of another person or with a technical assistance. You need to be able to maintain your balance. You need to be able to walk. You need to be able to get up and down from a chair or bed. You need to be able to take stairs to drive or take public transportation or get a ride. And so all of those things actually are important. But maintaining balance is, you can't do all the other things on the list unless you can maintain your balance. So balance is really central to mobility. Now balance is controlled by several systems. So there are three sensory systems that provide feedback to your brain and your central nervous system that your brain then will act and tell your musculoskeletal system to make a compensatory movement so that you don't fall down. And so the three sensory systems are your visual system, your somatic sensory system. So your ability to feel the ground with your feet and your vestibular system. So if you look at this man standing here on one foot, doing a yoga pose. All three of those systems are helping him to determine very quickly whether he's maintaining his balance or not. And if he's not, then his brain is telling his ankle muscles and his hip and his lower leg muscles to act and to compensate for that loss of balance. So I just want to summarize some of the previous research that's been done on vision and balance and this is certainly not an exhaustive list. I wanted to focus on some of the prior work that I've done, as well as some, some, I'd say seminal publications. I do want to point out a couple years ago, Afshin and I published a paper using the cross sectional CLSA data, and we found that people with worse acuity were more likely to fail the balance test and we actually saw an interaction with peripheral vascular disease in that paper. And some other work I did in 2008 during my postdoctoral work with Sheila West at Wilmer Institute in Baltimore. This was done using the Salisbury I evaluation study so this was made mainly an eye study. And so they measured all kinds of different types of visual function. All of those types of visual function that are listed there were associated with worse balance. So worse acuity was associated with worse balance, worse contrast sensitivity. When you put all the vision measures into a model together and tried to CR8 because a lot of these are correlated with each other. When you put them together, it was actually motion detection that remained significantly related to balance, whereas acuity and contrast sensitivity, sensitivity were no longer significant visual field remains significance for one of the types of stands so visual field and motion detection appeared to be more important than acuity and contrast sensitivity. Another study by a different Dr West found that visual field and contrast sensitivity were important in a study in Australia. Also found contrast sensitivity to be important. So what about research looking at particular eye diseases and balance. And so most studies looking at eye disease and balance have been done in the ophthalmology clinic rather than using a population based sample. The first two studies here only had glaucoma patients in the sample so there was no control group without glaucoma. But the study by Pradeep Ramaloo at Wilmer. He found that in patients with glaucoma those people who had more visual field loss had worse balance. And the same thing was found in the Newman study now in the Newman study they looked, not it how long you could hold a balance stand, but they looked at something a bit more sophisticated called postural sway. And so this you stand on a platform and they can measure very precisely the amount of sway that you're going back and forth. And basically confirmed what there it was the same finding that more visual field class loss more postural sway. And then a study that I did in Montreal a few years ago, where we had we compared people with eye disease to people who had relatively normal vision. And we found that people with glaucoma had worse balance than those with normal vision. We did not find that people with AMD had any difference to their balance compared to people with normal vision. Now what about longitudinal studies. So up to this point I've just been talking about cross sectional research. You know longitudinal studies are important when you're trying to say that something like vision loss causes something else so something's causing something it's there before the onset of the disease, or the problem. And so, ideally you'd have longitudinal evidence saying right these people have vision loss and over time their balances is getting worse. Now there aren't a lot of longitudinal studies that look at this. There are a couple of studies that did have found no association between visual acuity and change in balance so they, that was the only measure of visual function that these studies had. You can see they're rather small sample sizes so that could have played a role. One study that did find an association one longitudinal study was using the epi's data so that stands for established populations. I'm forgetting what it is but it's a famous study done in the United States. And the great thing about the epi's data is that they included institutionalized people in their sampling frame. So when you have institutionalized people you actually can get enough people who are who are blind to study them as a separate group and so what they found was that very severe vision visual acuity loss, like blindness was associated with developing more mobility limitations, which included balance loss. So, if I had to summarize the literature I would say there, there haven't been a lot of longitudinal studies that have looked at this, and the longitudinal studies have been a bit conflicting. Some of the studies had small sample sizes. So they may have been a bit underpowered. And some of the studies on eye diseases didn't have a comparison group of people with normal vision. There weren't, I didn't find studies where they compared people with cataracts with people without cataracts. There are some studies looking at cataract surgery, which I'll talk about later, and some studies that look at simulated cataract. So what I wanted to do in the CLSA was look at the longitudinal relationship between visual acuity and eye disease with the onset of balance problems. And my conceptual framework is shown here so I wanted to look at visual acuity or eye disease at, let's say baseline, and then I wanted to look at a group of people who, who had good balance and then developed bad, worse balance. So over, this was over a three-year period. And so whenever you're using observational data, you need to account for confounders. So confounders are variables that are associated with both your exposure, so the vision loss, and the outcome. So the balance problems, but are not in the causal pathway. And so the biggest variable that you always have to worry about when you're doing aging research is age. So these are variables that we looked at included smoking and sex and body mass index and health conditions like diabetes and stroke and limitations and activities of daily living, which represent disability. So we use the comprehensive cohort of the CLSA. So this included 30,097 adults ages 45 to 85 from across the country. And we use the comprehensive cohort because visual acuity was measured at the data collection site in the comprehensive cohort. And so the baseline and follow-up data were separated by three years. So just keep in mind who is in the CLSA versus who is not. So people were excluded from the CLSA if they were in an institution, if they were living on a First Nations Reserve or settlement, were in the Canadian Armed Forces, did not speak French or English, or had obvious cognitive impairment at baseline. And so these are, this is a map of the different data collection sites, and you can see they're spread very nicely across the country, but not nothing in the far north. So people were randomly sampled using provincial health registries, along with random digit dialing and stratified sampling was done to ensure adequate representation of various demographic groups. And so visual acuity was measured using the chart shown here, which is called the ETDRS chart. This was two meters from the participant. And it was measured binocularly so with both eyes open as well as monocularly so one eye at a time. And people wore their normal corrective lenses for distance when they took the test. And then the scores were converted to log Mar, which stands for log of the minimum angle resolution, and this is the way acuity is analyzed. And so a log Mar of zero would be equivalent to 2020 vision and a log Mar one would be equivalent to 2200. And so one line on this chart which is five letters would equal point one log Mar. Participants were also asked if a doctor had ever diagnosed them with the following so cataract glaucoma and macular degeneration. If they said they had cataract, they were asked if they currently had a cataract. And so if people said no, we assumed that they had had cataract surgery balance was assessed using the one legged stand test. And so this test has shown good reliability. And it's also predictive of injurious falls and incident disability. And then they did. First of all, they were excluded. If they could not stand unassisted, or if they use the cane or a walker. And then they removed their shoes, and they stood one meter from a wall and raised the right leg up to the calf of the left leg and put hands on waste. And so they were asked to do this for at least 60 seconds and then the timer was stopped at 60 seconds, or the timer was stopped when a person lost their balance, like they had to put their leg down or if they touched the wall. And so we use the better time of the right and left legs in the analysis. And so the demographic variables were collected by self report. And then we categorized body mass index. Body mass index was measured so height and weight were measured and put into kilograms per meter squared. And then we categorized body mass index just because it often has a nonlinear relationship with various health outcomes. And so our reference category was what's considered to be normal weight. So that's 20 to 24 kilograms per meter squared. And we looked at health conditions that we thought would be particularly relevant to both vision and balance. And so like stroke and diabetes. And we looked at limitations to activities of daily living in a yes no way so if anyone said that they could only do certain activities with help or not at all. They said they had limitations in ADL so these are activities like getting dressed or eating or walking or getting out of bed. And so, if people failed the balance test that baseline they were excluded because we were interested in the new onset of balance problems, and we defined our outcome in terms of two groups so did they fail meaning they could not stand for 60 seconds at the level of data collection, or did they not fail, they, they could stand 60 seconds. We also did a sensitivity analysis, instead of using 60 seconds, we use 30 seconds. And so with a dichotomous outcome like this we use logistic regression, and we accounted for the complex study design within state using the SVY prefix. I just want to talk about who exactly is in my analytical sample so there are 30,097 people in the comprehensive cohort. Some of them did not return to follow up for various reasons. Some of them did not take the balance test at baseline so they, they may have been using a cane or a walker for example. And then a number of people like just under 50% failed the balance test at baseline so they are not in our sample, because we're interested in the new onset of balance problems. And then some people were missing data on balance at follow up so when you take away all those groups you end up with 12158 people. And so that is our analysis sample. I just want to show the distribution here of the better leg time on the baseline balance test so those of you trained in statistics will note that this is not a very pretty distribution. It's very far from normally distributed. It is truncated at 60 seconds, and about half the people at baseline were, were able to stand at least 60 seconds. To use linear regression on a distribution like this, that would not be advised. We chose to use logistic regression with a cut off at 60. But of course that means we're losing some information on those people who stood for less than 60 seconds. So we, we chose to dichotomize the dichotomize this. If you're interested in doing analyses on balance in the future. I just learned recently that there's a type of regression for truncated data and so that might be something you'd want to look into. Alright, so, first of all, I want to compare who's in my analytical sample to who's not in the sample. So, these are people who either failed the balance test at baseline or did not return to follow up. And so, not surprisingly, these people are quite a bit older. They're likely to be obese and to have health problems. They did have somewhat worse vision so you can tell that by comparing the log more so, as I mentioned, a log more of, of zero is 20 20 vision. If it's negative, then that means they have vision better than 2020. And as it goes closer to one vision is getting worse. So also somewhat more likely to have eye diseases like cataract AMD and glaucoma. Okay, so now let's compare in the analytical sample the 12158 who passed the balance test at follow up, compared to who failed the balance test that follow up so 22% of people failed the balance test that follow up. And so they just like the previous slide they were older. They were more likely to be obese. They were more likely to have health conditions. And some of you might be interested in the proportion who failed the balance test by age group. So in the, the lowest age group of 45 to 54 about 10% failed the balance test. In the oldest age group, more like 65% failed it so you know the ability to do this test does decrease with age. All right so now let's look at vision variables and it's their relationship with failing the balance test that follow up. So people who had people who failed the balance test had worse visual acuity. They were more likely to have cataract either in the past, meaning they had cataract surgery. Currently, or we had a group of people who, when they were asked to you still currently have a cataract they did not know. And so there were so many of them that we made a separate category because we didn't want to exclude them all. And so that's what that group is there and so all three of those groups. There was a higher percentage in the, in the people who failed the balance test. And then people with AMD and glaucoma were slightly more likely to fail the balance test. And so what about when we use regression so, you know, we want to adjust for age certainly and these other factors as well to make sure that any relationship between vision variables and balance is not due to confounding and so when we use regression, we saw an odds ratio of 1.15. It was statistically significant because the confidence interval excludes one. And so the way you interpret this is that for each line worse that someone performs on the visual acuity test to have a 15% higher odds of failing the balance test that follow up. So what were the odds ratios for the other variables in the model so I'm showing everything except stroke and province are not being shown here everything else is being shown on the screen and so older age was associated with failing the balance test. Female sex, current smoking, both being overweight and obese was associated with failing the balance test. Type one diabetes has a very high odds ratio type two diabetes is also statistically significant and people with ADL limitations are more likely to fail the balance test. So what about when I add the eye disease into the model. So, you know, we don't have acuity in the model we just have the eye disease. So if people with cataract are more likely to fail the balance test and our results for cataract were sort of surprising so I expected cataract to be associated with failing the balance test and it was with an odds ratio of 1.31. I did not expect the group who said they did not currently have a cataract to have an interest odds of failing the balance test. They actually had the highest odds ratio. And then the group with the status unknown, they, there was no association. So with AMD, so with AMD, we did not see any association. The odds ratio was very small at 1.05 and was not statistically significant. And with glaucoma we did not see an association, also not statistically significant. So we did some sensitivity analyses. Just to see, well, what if we use a 30 second cutoff do we, you know, are the results sensitive to what cutoff you pick and basically the results were essentially the same when using a 30 second cutoff. We also looked at whether cataract surgery remained associated with balance after adjusting for visual acuity and cataract surgery remained associated but current cataract did not. So we also looked at whether cataract surgery remained associated with balance after adjusting for other diseases like AMD and glaucoma, and it did. All right, so let's just summarize what we found here. So we found in agreement with many cross sectional studies and the host field longitudinal study, we found that visual acuity was associated with failing the balance at follow up. So this is really important because a lot of visual acuity loss is probably easily treatable due to refractive error or cataract. And so, if, if we can improve the visual acuity of people we may also improve their balance. Why was there an elevated odds ratio for cataract surgery. Now we went through a number of potential explanations ultimately we were not able to explain why there was an elevated odds ratio for cataract surgery. Let me just talk about some of the explanations that we thought about so we thought maybe there could be an elevated odds ratio for cataract surgery because maybe people were in between their first eye cataract surgery and so they had a real difference in visual acuity between their two eyes. And so we tried adjusting for the difference in the monocular visual acuities and thinking that if that were the case, the association between cataract surgery and balance would go away. It didn't go away so we don't think it had to do with that. We also thought well maybe people have had, you know, both of their eyes operated, but they still have uncorrected refractive error maybe the surgeon was not able to remove all of their refractive error. And so we adjusted for binocular visual acuity. And again, the association with cataract surgery did not diminish. We thought well maybe they have other ocular disease besides just cataract. And, and perhaps that other ocular disease is causing that cataract surgery odds ratio to be elevated. So we tried adjusting for AMD and glaucoma. That did not make any difference but of course we don't have data on other types of eye disease. We thought well maybe it has to do with other health related differences you know we adjusted for differences in ADL limitations as well as stroke and diabetes, and that didn't have any effect on the odds ratio for cataract surgery. Maybe there are other health related differences that we're unaware of. Maybe it has to do with misclassification so we are relying on self reported data for cataract and cataract surgery. Maybe people thought they had cataract surgery but they didn't. So that's one possible explanation. And then finally, perhaps people who had cataract, even the cataract removed by surgery have worse vestibular balance. And so there's actually some evidence for this explanation by Purdue Ramalou's group at Wilmer. They looked specifically at vestibular balance by having people stand on a compliant surface meaning like foam with their eyes closed. So the only sensory system they had to help maintain their balance was the vestibular system. And they found that people with vision loss either due to refractive error or eye disease, both groups had worse vestibular balance than people without vision loss. And so it could be that, you know, something about having cataract for a while distorts the vestibular balance system and then even after the cataracts removed, perhaps it doesn't go back to normal right away. And so, you know, those are some possible reasons why we saw an elevated odds ratio for cataract surgery, but they require more investigation. Ultimately what we really need with the CLSA is to be able to confirm whether cataract surgery occurred as well as confirm the occurrence of other ocular disease like AMD and glaucoma. And we need to do that using by linking to health administrative data. This is something that I want to do but it requires funding. Now our finding is consistent with a study done in Australia using health administrative data. It was a retrospective cohort study and what they found they didn't look at balance but they looked at the risk of an injurious fall requiring hospitalization. And they found that the risk of that doubled between first and second eye cataract surgery when compared with the two years before first eye surgery so they didn't compare to people who didn't have cataract surgery. They compared to the period before a person had their first eye cataract surgery. Now I'm not so sure about the study design. It seems like a design that could be a bit prone to selection bias because if you did have an injurious fall requiring hospitalization, you might not have gone on to get cataract surgery because you were in bad shape, you know you weren't strong enough to get that cataract surgery and so I'm not so sure about their study design but it is consistent with what we found. They also found an increased risk of injurious falls after second eye cataract surgery. But our finding was not in agreement with other studies so there has been a randomized controlled trial where they looked at expedited cataract surgery compared to usual time cataract surgery. They also found that those people who had expedited cataract surgery had a reduced risk, not of a first fall but of a second fall. Our results are not in agreement with a study by McGuinn, which showed they found no association between cataract surgery and the self report of falls or balance problems. The self report is not as good as measuring a balance problems. And it's not in agreement with a study by Schwartz, which looked at postural stability after cataract surgery. And they found that it improved when people had their surgical eye open compared to what it was before the cataract surgery. So to conclude I just want to say you know cataract surgery is a very safe and effective surgery in no way am I saying people should not get cataract surgery cataract you should definitely get your cataract removed. But it is important to further investigate our finding. So there are, there's been a lot of research done looking at interventions that can be used to improve balance. And so this is just one systematic review that looked at various exercise interventions so things like Tai Chi and yoga and strength training. These things have all been shown in clinical trials to improve balance and people and so these are things that could be suggested to people who have vision loss. The drinks of this research include the longitudinal study design with the three years of follow up the very large population based sample and the measurement of visual acuity and balance. The limitations are that there was no full ophthalmological exam or access to medical records or health administrative data. So I disease status was based on self report. We only have measured visual acuity. So there's no data on contrast sensitivity or visual field which are also very important measures of visual function as it relates to mobility, and the data on cataract, you know is limited we we don't know. You know we don't have eye level data on cataract we just know at the person level, and many people did not know whether they still had a cataract in the eye or not. And so, as far as clinical significance of this work, I think more attention needs to be paid to potential balance problems in older adults with vision loss, because there are interventions available that can improve balance, and that should be considered. So if you're interested in learning more about this work, it has been published in the American Journal of ophthalmology a few months ago, and I'd like to acknowledge my co authors, particularly my students Zana Cahill and Alyssa Grant, and my clinical collaborators doctors, Oba and Dr. Gwatt in in Montreal and Dr. Berman in Ottawa. And so the data sets that were used to conduct this analysis are listed here, and I'd like to acknowledge the principal investigators of the CLSA doctors rena Wolfson and Kirkland, and I'd be happy to take any questions now. Thank you so much, Dr. Freeman. I do. We do have a few questions that came through the chat box the q amp a box at the bottom. Again, if you have any questions please submit them there and then we can, it's a lot easier to keep track of them in the q amp a box. So the first one from leader Malinowski ophthalmologists when doing I exam say there, say that there are the beginning of signs of cataracts but there, but that it is not right yet what does that mean and or I drops recommended in advance of surgery. Yeah, so if someone, you know, a surgery will not be done on a cataract until it reaches a certain state where it's thought to be, you know, causing you problems. And so we don't use eye drops for cataract people will will be signed up for surgery if you did have eye drops they would probably be to prevent infection before or after surgery. But yeah, if someone were told, you know, you have signs of a very early cataract, would they report that on the CLSA. I'm not sure. Or would they only report a diagnosis once their, their cataract is is so advanced that they're about to have surgery. So that is one of the limitations of relying on a self report of disease like cataract, because it is a very slow growing cataract and it's only when it becomes severe enough where it would really be a diagnosis of cataract. Okay, and another question from Lida, can you assess the 400 meter walk while using the cane. Yeah, so I, you know, assessing the 400 meter walk, you know, you do require access to a track, you know, a lot of times people will do, you know, a much shorter walk in the hallway of a hospital. And in that case I, they might let you use the cane to do that. If you felt safe, certainly for the balance test, they didn't let anybody do the balance test if they had a cane probably for safety reasons. But yeah, I think you could, you would want to see what people have done with the 400 meter walk I'm sure in that paper by Newman, they probably mentioned if they excluded people who use the cane or not you'd probably want to be consistent with what they've done. Next question is from in the Q&A boxes from Andrew Patterson, is I specific, so left or right side data available for cataract, for example a subject could have cataract in both eyes but removed in only one. Yeah, so that's one of the limitations they were just asked have you ever been diagnosed with cataract, and do you currently have a cataract so we don't know if, you know, they had one cataract removed and one still in the eye or if this was the first cataract so we don't have eye level data, unfortunately, we would if we linked, well, no, even if we linked to health administrative data, you know you'd have to look for the two separate cataract surgery procedures to know. Okay, and a follow up question to that. Also by Andrew Patterson are time since last routine ophthalmology exam I'm not, my words aren't coming out right now, available in the CLSA. Yes, so there is a variable that asks about eye care so have you had eye care in the last year I believe. And yeah, we've we've worked with that variable before. Okay, I don't see any other questions I do see a question in the chat. So I'll follow up on that can you prevent molecular degeneration, and if so how. Can you prevent age related macular degeneration. So, that's a good question. So we know that it is highly heritable and there have been a number of genes found to be associated with it. There are also environmental factors that are associated with AMD as well. And so I believe there's research on fish consumption and exercise and various modifiable risk factors that you can look at certainly. Yeah, if you wanted to send me an email I could give you a quick rundown of all the different environmental factors but yeah there are things that you could probably do to try to lower your risk. So there is a very strong genetic component. Thank you. The next question is, is it possible that the amount of time spent with untreated cataracts contributed to the poor vestibular functions or poor balance in cataract surgery group, or the difference in time between left right eye cataract surgery. I think that's definitely a possibility I think, you know, a person could have had, you know, impaired vision due to cataract for many months or even years and so that may have affected the vestibular balance system. And so yeah it would be great to know how long they they had the cataract and how disabling it was. That would all be interesting information, but looking you know at the connection between eye disease and vestibular balance is would certainly be interesting. Just a comment by one of our participants who he says having had cataract surgery I can imagine that some of the unsure status might be due to the possibility of recurring cataracts after surgery. I think that's a good point. So yeah once the lens is removed and you have the artificial lens, the cataract shouldn't come back although I think there are complications of cataract surgery where you can need additional surgeries. I would need to talk to an ophthalmologist more to talk to you more about that. Okay. I don't see any more questions. So I think we're going to finish up a little bit earlier. If a last question comes in while we're doing our wrap up perhaps Dr Freeman can stay on and we can answer it or we can also she can also follow up to with you via email. So I'd like to start wrapping it up then by again thanking you. I'd like to highlight your participation in the CLSA webinars both the present our presenter as well as our participants. I'd like to remind you that the next deadline for data access applications is March 30 2022. You can visit the CLSA website under data access to review the available data, as well as additional details about the application process. I'd like to remind everyone to complete their anonymous survey upon exiting the zoom session. If it hasn't come up already. And the upcoming CLSA website for your information will be Tuesday, February 22 at 1pm. The title will be examining mechanisms underlying the association between adverse childhood experiences and health outcomes in mid to older aged adults in the CLSA, and this will be presented by Dr Divya Joshi postdoctoral fellow in the Department of Health Research methods evidence and impact at McMaster, and you can find registration details on our website. I think it's on the on the screen there. And remember the CLSA promotes this webinar series using the hashtag CLSA webinar. And of course we invite you to follow us on Twitter, Twitter at at CLSA underscore EL CV. So that brings us to the end. Hopefully we see you and or you at least hear us next month for our February webinar and thank you again to our presenter. Thank you very much.