Season 2 | Episode 4
>> Dr. Garg: I really don’t know where this blue light blocking obsession has come from. As far as we know, the blue light blocking glasses do not protect a person’s eye in any way because there is no clinical data to suggest that blue light from our phones or our tablets is harmful to the eye.
>> Joe: Hello, and welcome to the Merck Manuals Medical Myths podcast, where we set the record straight on today’s most talked-about medical topics and questions. I’m you host, Joe McIntyre, and, on this episode, we welcome Dr. Sunir Garg. Dr. Garg is a professor of ophthalmology on the retina service at Wills Eye Hospital in Philadelphia. He is also on the editorial of the Merck Manuals. Dr. Garg, thanks for joining us.
>> Dr. Garg: Thank you for having me, Joe.
>> Joe: So, today we’re going to talk to Dr. Garg about all thinks eyes, including some of the most common myths people have about their vision. Now, let’s first start off with a myth we see, no pun intended, quite often. It’s this idea that so-called eye floaters are dangerous and a sign of a serious condition. Dr. Garg, can you first explain to us what eye floaters are and if there’s something to be worried about?
>> Dr. Garg: Eye floaters are one of the more common things that people come in to see us for, and there’s a couple of different types of floaters that people experience. The typical ones are floaters that people get as they get older, and people generally see them as hairs or bugs that float or move in the vision. The reason that people get floaters is because the eye is filled with a vitreous gel, and, just like Jell-O, that gel is mostly water with some spiderweb materials, some collagen that holds that jelly together. And, as we get older, like every other part of the body, that jelly starts to sag, and those fibers will clump up, casting shadows, and that’s what people see as the floaters. The reason that we care about floaters is not so much because they drive patients nuts, and they do drive patients nuts. It’s because as that jelly separates from the retina, it can sometimes pull on the retina, causing a tear in the retina. And a retinal tear is something that you want to have treated because, if it doesn’t get treated, it becomes a bigger problem called a retinal detachment. And when people get floaters, you know, if I’m going out in the snow or if I’m looking at the horizon on a sunny day, you know, even I’ll get some floaters. Those aren’t the kind that we’re so much concerned about. The type of floaters that we care about are people sitting around, minding their own business and they suddenly get a lot of floaters that hang out for twenty-plus minutes, sometimes accompanied by a flashing light in the corner, sort of like a kid playing with a light switch. The most ominous thing would be a dark black curtain or cloud coming into the vision. That’s the reason that we encourage patients to get checked for floaters, and, as people get older and they get floaters, it’s something that they should get checked. You know, it’s not a middle-of-the-night emergency, but it would be worthwhile an 8 AM phone call in planning getting seen, you know, sometime the next couple of days if you can.
>> Joe: So, it’s not necessarily nothing to worry about, and it’s not necessarily something to always worry about, but it really depends on your unique situation?
>> Dr. Garg: Exactly. So, for most people, you know, the news ends up being good. It’s really a safety check. We reassure in 95% of people that everything looks great and go on your merry way. But, for a few percentage of people, we are really happy when they come in early because, if it’s just a retinal tear, we can typically fix it in the office in about 5 minutes, and people then go on their way and are able to protect their vision with very little inconvenience to the patient.
>> Joe: Now you mention this idea that people may get these floaters in their eyes as they get older. What does happen to your vision as you age? Is it just an inevitable part of aging, that your vision will change? Or is it a little more complicated than that?
>> Dr. Garg: For most people, as they get older, the vision definitely does change some. If people are nearsighted, and sometimes nearsightedness starts when you’re young, they need a new updated prescription every year until they’re kind of early adulthood. And, then, most folks, when they get around forty to fifty years of age, will start to need reading glasses, and those are the cheaters you can get at the dollar store or bifocals, and I just got my own bifocals a few months ago since I’m now in my late forties. And, then, the vision for most people tends to be pretty stable up until they get closer to retirement age, and then people get cataracts. But, thankfully, we can do great things to help people with their cataracts by doing cataract surgery. And, most patients should expect to have good vision, maybe with the help of glasses or contacts, for their whole life. Obviously, other conditions, such as macular degeneration, glaucoma, diabetic eye disease, what have you, can occur along the way, and, luckily, ophthalmologists are there to help those folks.
>> Joe: Can you explain to our listeners what exactly macular degeneration is?
>> Dr. Garg: Yeah, macular degeneration is one of most scary terms that I think most older Americans will hear because, when they hear it, they think that they’re going to go blind. But, for the majority of patients, that couldn’t be farther from the truth. If the eye is like a camera, in the front of the eye you have a lens, and that’s the cataract. In the back of the eye, you have the film. That’s called the retina. The center part of the retina is so important that it gets its own name, and that’s called the macula. So, everybody has two maculas, and for the majority of the time, the macula stays healthy throughout a person’s life. But, as we get older, a number of things can happen that affects the health of the macula, and one of those things is called age-related macular degeneration. The typical way it starts off is by the development of aging spots, really similar to some of those aging spots that people get on the back of their hands when they get older, and those aging spots for a lot people are just a sign that they’re getting older but don’t affect their vision in any way. In some folks, however, those aging spots continue to accumulate, and those aging spots both indicate to us that the macula is not working all that well, and the aging spots themselves can damage the macula. And, over time, sometimes those aging spots cause damage and can affect the vision. That process is called dry macular degeneration, and we can talk about that a little bit more in a moment. And, then, some people develop a second form of macular degeneration in which an abnormal blood vessel starts to grow underneath the macula, and that blood vessel leaks plasma or blood, and that makes the macula wet. So, we call that wet macular degeneration. And, we have treatments for that, and some of your listeners may know some of their older family members or friends that come in to a retina specialist’s office to receive treatments. Those treatments are kind of spooky. They’re injections that we give patients in the eye of a medicine, but that can typically stop the wet macular degeneration, and, for a lot of people, undue that damage and help improve the person’s vision.
>> Joe: Now, as you mentioned before, we talked about this idea that, as you get older, more people tend to get glasses, whether that’s bifocals, whether that’s simple reading glasses. Can you tell me, does wearing glasses too much throughout your life make your eyes dependent on them?
>> Dr. Garg: Yeah, people have often sort of wondered that, and, as far as I can tell, the answer is no. To me, wearing glasses is sort of like wearing shoes. You wear them because they help you, and they can help you function better, so it’s just a tool. And if people find that glasses enable them to see better, they should wear their glasses. The folks that’ll typically say that, oh, if I wear my glasses, I’ll become dependent on them, are people who are in that mid-forties era where they’re transitioning towards needing reading glasses. Those folks tend to think, oh geez, if I wear my reading glasses, I’m going to become more dependent on them. But, what’s happening is they’re getting older, and, as they get older, they’re ability to focus up close starts to diminish and so they’re becoming more dependent on their glasses because they’re getting older, not because they’ve been using the glasses in the first place.
>> Joe: Now, speaking of glasses, we’ve seen a lot, I’m sure, online and in the media, this idea of blue light and how blue light damages our eyes. And, I’m sure many people have seen these blue light glasses that supposedly protect your eyes from blue light, whether it’s on your phone or on your computer as you’re staring at your desktop all day. Do they do anything? Do these blue light glasses actually protect your eyes in any way?
>> Dr. Garg: No. As far as we know, the blue light blocking glasses do not protect a person’s eye in any way. And I really don’t know where this blue light blocking obsession has come from. If you go to any of our conferences, it’s not like we as a community of physicians are sitting around, worrying about this problem because there is no clinical data to suggest that blue light from our phones or our tablets is harmful to the eye. The only studies people quote are studies done in a petri dish or on a poor animal in a laboratory where they shine a very intense blue light, many, many times, a hundred times, and, in some cases, a thousand times more than we would ever get from our phones on to these cells directly for hours on end. And in that scenario, it could be harmful, but, with the amount that we get from our phone, it’s much, much less than the amount of blue light than we would get from the sun because blue light is one of the major constituent wavelengths from the sun. And so our eye has evolved to do a pretty good job blocking a lot of those higher wavelength lights, and the amount of blue light from our phone or our tablet is much less than what we became accustomed to by being outside. What people experience when they use their phone or tablet a lot is their eyes tend to dry out. And when people look at a young kid who’s playing a video game, if you look at that kid, they’re just staring at the screen, and they don’t blink for minutes on end, and that happens to adults, too. When they’re on their computer for a long time or on their phone, they don’t blink a lot, they don’t move their eyes around a lot. So the eyes tend to dry out and become fatigued, and that’s what’s bothering people. It’s not the blue light itself. So, the American Academy of Ophthalmology has what we call the 20/20/20 Rule. And we recommend that patients, every 20 minutes, take a 20 second break, and look 20 feet off into the distance. And doing that, what stops the eye from staring three feet away, gets people to move their eyes a little bit and gets them to blink a lot more. And I think if people did that, the fatigue that they’re getting from the phone would go away, and so the culprit is just doing that activity, not the blue light itself.
>> Joe: So, you’re telling me that, when my mom would yell at me growing up, saying, don’t stare at the TV too long or don’t sit so close to the TV, I was actually the right one all along?
>> Dr. Garg: Don’t tell your mom, she’s going to get mad at me. But basically that’s correct. But there is one bit of clinical data that blue light might play an important role, and that’s regulating the sleep-wake cycle. So, traditionally, when we were linked to the sun and the sun rhythms, and that started to change when we got indoor lighting, the body became accustomed over tens of thousands of years of evolution to start waking up when you got light in the morning, and then most of us were out during the day, and blue light exposure during the day is pretty intense. And then as the evening came by, wavelengths started to shift from blue more towards red and orange. And our circadian rhythms, or our sleep-wake patters, got hooked up to the sun. What’s happening is, now that we have electricity all the time, we have internet 24/7, people are using their devices later and later into the evening. And the blue light from our devices may impact the sleep-wake cycle and the circadian rhythm for some people. And so, if people find that they’re sleep is disrupted, perhaps having yellow tinted glasses that you can buy inexpensively at the store, or switching their phone over to a night mode, which changes the color spectrum a little bit, may help with the sleep-wake cycle. And so that’s helpful in the hour, two, or three before bedtime, to mimic more natural sun rhythms. There may be some benefit to that, but for standard blue light blocking to help protect the eye balls, there’s no evidence that that’s needed.
>> Joe: We have to take a quick break, but we’ll be back with more from Dr. Garg right after this.
>> Joe: The Merck Manuals website offers a variety of video, audio and interactive content. With so many choices, it’s easy to access information as the best, first place to go for free, understandable, medical content.
>> Joe: So, talking about eye health really quickly. I’m sure a lot of us heard growing up that this idea that carrots, when you eat carrots, it’s much healthier for your eyes. It helps you see either in the dark, or it helps you see better, or it’s better for your eyes in general. Is that actually the case?
>> Dr. Garg: Carrots and other good fruits and vegetables are helpful to the eyes, and that’s absolutely true. We know that carrots have Vitamin A in it. Vitamin A, you know, a lot of us think of Vitamin A as like this single, one vitamin. I can go to the drug store and buy a bottle of Vitamin A. But what we found is that there are multiple, different sub-types of Vitamin A. Some of the listeners may have heard of lutein or zeaxanthin, in addition to Vitamin A. And those are very, not just helpful for eye health, but they’re critical for the function of the macula and the retina. And carrots are good. Over time, we’ve come to realize that dark green, leafy vegetables like broccoli, spinach, kale, collard greens, mustard greens, are actually probably more rich in Vitamin A than carrots are. And it’s a good idea for everybody to eat a well-balanced diet. We think that at least three servings a week of those dark green, leafy vegetables is helpful for people. We know from a number of studies that people who ate those dark green, leafy vegetables at least three times a week had a much lower chance of developing macular degeneration as they got older than people who did not eat those vegetables, and so that’s very easy. Carrots are good for you. Other foods high in antioxidants like berries are also good. To some degree, a well-balanced diet that’s high in the good stuff and less in processed foods is good for every part of the body, including the eyes and eye health.
>> Joe: Can you explain to us what the various levels of blindness are, and if people who are quote-unquote legally blind always see black or if is something a little more complex than that?
>> Dr. Garg: It’s more complex than that. When you think like an ophthalmologist thinks, people say, oh, without my glasses I am totally blind, but with my glasses I see great. That’s not totally blind. Or people will say, oh, without my glasses, my eyes are bad. That’s not true, either. If glasses is what your body needs in order to see well, so be it. So that has nothing to do with blindness. There’s two different things that can affect whether people are considered legally blind, and legally blind is defined as: vision is 20/200 or worse. So, when you come into our office, people are familiar with the big EMEI chart. That’s 20/400. The next set of letters is 20/200. If you can see just those two letters but nothing more, than you’re considered legally blind. The second thing that impacts a person’s definition of legal blindness is how good they’re peripheral, or side, vision is. And if that peripheral or side vision starts to go bad, that can also make you legally blind. But most people who are legally blind, and one of the more common things that we see is people with macular degeneration, meaning, if I’m sitting across a table from somebody, I might not be able to see their facial features very well, but I can typically see their hair. I can see their chin. I can see all around them, so that will impact my ability to see people’s faces, to watch things on TV, and maybe to write in my checkbook. But most people who are legally blind have plenty of vision. They get up, make a cup of coffee, make their toast, get dressed, go for a walk. They just have trouble with facial recognition, doing their checkbook, and, of course, getting a driver’s license.
>> Joe: Is it dangerous to stare at the sun without sunglasses on? I know we had some issues with people staring at the sun during the eclipse. How dangerous is it to stare at the sun, one, and then just in general to be outside when the sun is out and bright and shining? Is it dangerous to not have sunglasses on?
>> Dr. Garg: It is always a bad idea to stare at the sun. There’s no scenario in which looking at the sun with your naked eyeballs is a good idea. When I was a kid, I had a magnifying glass, and it doesn’t take a kid very long to realize that, if you take that magnifying glass on a bright day, you can start focusing that light and making it really bright and start setting things on fire. And the front of the eye functions like a magnifying glass. And it will concentrate that light and that heat at the macula, and that heat, just like it would burn a leaf on the magnifying glass, is hot enough to damage the central vision permanently. And we’ll see that around the time of the eclipse. Professionals did our best to educate everybody about the harm of potentially doing that because even that bright light from the edge of an eclipse can be damaging to those central cells. And people will then say, doc, when I’m reading words, letters go missing, and some people are lucky and those cells recover, but, for a lot of people, they will have permanent damage. So the only safe way to look at the sun is by wearing special glasses that block the vast majority of the sun’s rays. Typical sunglasses are not protective enough, and people should not look at the sun directly even with their sunglasses on. Sunglasses themselves for regular wear, I’m going outside, I want to wear the sunglasses, the data on that is a little bit more variable. There are some studies that suggest that sunglasses are protective, but other studies suggest that maybe not so much. If people are going to wear sunglasses, they should make sure that it has both UV-A and UV-B protection in it. Those are the wavelengths that may be more harmful to the eye than others. But, for me, when I go out in the sun, I do not wear sunglasses for my ocular health because I just don’t find the data to be that compelling, but other people may disagree with me on that one.
>> Joe: Now, I may bust this question right away by giving away some details, but I’m going to ask it anyway. I myself have brown eyes, but have a bit more sensitivity to light than my wife does, who has green eyes. Is there any way that someone’s eye color impacts their sensitivity to sunlight?
>> Dr. Garg: As a rule of thumb, the answer is no. There’s a lot of variability, and some people are more sensitive to light than others, and we don’t fully understand why. People who have lighter-colored eyes may be a little bit more light sensitive, partly because their pupils may dilate a little bit more, and they may have a little bit more trouble adapting to some of the bright light. But, as a rule of thumb, it’s really specific to that person and not necessarily specific to people with a certain eye color.
>> Joe: Now, speaking of other people’s eyes, does wearing someone else’s glasses, if it’s not your own prescription, have a chance of damaging your own eyes and your own vision?
>> Dr. Garg: Nope. As an adult, there is no problem. It’s like wearing somebody else’s shoes. It might not be so comfortable, it might not work as well for you as your own shoes, but you’re not going to hurt yourself by wearing somebody else’s shoes. Similarly, wearing somebody else’s glasses isn’t going to cause a problem. It may make your eyes more fatigued. It may give you a little bit of a headache, but it won’t hurt you. Obviously that’s different if you’re a child. In a child, you want to make sure they’re wearing they’re glasses appropriately because they’re brain is still, and they’re eyes are still getting hardwired to each other. But, as an adult it doesn’t matter.
>> Joe: Now, back to people with vision impairments really quickly. Are people who are so-called colorblind, do they see only black and white or are there various levels that describe how people see different colors?
>> Dr. Garg: So, when I was younger, I thought that color blindness meant you were watching the Andy Griffith show where everything was in black and white. But that’s far from the truth. The eye has two groups of cells that help us see. Our central vision does most of our color vision, and those cells are made up of red, green and blue cells, much like our TV or our screens are made up of red, green and blue pixels. And then our peripheral, or side, vision has cells that do more light versus no light. And, when people are colorblind, typically it’s one or two of their color cells that don’t really work well. And so they can have trouble with certain colors. The most common type of color blindness is red-green colorblindness. So those people have a lot of trouble with stoplights, for example, where you have red and green. They’ll have trouble matching their clothes precisely. So, folks that have colorblindness still see color. It’s just different color than you or I might be used to, and they’ll have difficulty with certain tasks.
>> Joe: Now, another myth we may have seen, you can actually tell me if this is a myth or not, is this idea that eye whitening drops that are popular among the fashion industry are actually damaging to your eyes. Have you heard of these eye whitening drops that get rid of the bloodshot-ness, essentially, of your eyes, or is there any truth to the fact that they may be damaging to your eyes?
>> Dr. Garg: That’s a great question, and it’s become a little bit more of a complex answer than it used to be. It used to be that, if people wanted to get their eyes whiter, they would buy Visine. And using Visine once in a while is A-Okay. Where people got into trouble was if you used it regularly, there was a chemical in the Visine that the eyes then got used to, so the Visine stopped working, and then if you stopped the Visine, your eyes would get really red for a while. So if people are going to use something like Visine, that should be used sparingly. Then there was another thing that came out that was popular in East Asia for a while, where they would use a very strong chemical, a chemical that we use for anti-scar tissue purposes. And they would put that on the surface of the eye to make the eyes white. That would make the eyes look really white, but it can damage the quality of the blood supply to the surface of the eye, and that can create huge problems for people. So we’ll discourage people from doing that. And there’s a newer eye drop that’s become available, which is a very mild version of a glaucoma eye drop that we’ve been using for years. The generic name for that is called brimonidine, and it seems like the brimonidine drop can make the eyes white. And, as far as we can tell, the eye does not become dependent on it, and it does not appear to have any long-term ill effects. So, if people wanted to use that, and, for most people I would suggest that they don’t, but if people really wanted to, or if they were up late last night and have a business meeting or a wedding and want to put the drops in, I think looking for that drop would be a safe option for them to consider.
>> Joe: Now, you mention glaucoma. One of the treatments, I’m sure many people have heard, for glaucoma is this idea that marijuana use could potentially help folks who suffer from glaucoma. Is there any science behind the fact that marijuana may be one way to treat glaucoma?
>> Dr. Garg: If you’re smoking marijuana, the eye pressure does or can go down a little while you’re smoking it, but glaucoma’s there 24/7. So unless you’re smoking like Cheech & Chong or Willie Nelson where you’re basically toking up all the time, you won’t get a sustained effect from it. So, if people want to treat the glaucoma, they should treat the glaucoma with the standard way that we do, which is with medicines, with laser or with surgery, and not by smoking marijuana.
>> Joe: So, as we wrap up here, Dr. Garg, I’m sure a lot of people have questions about their general eye health, how to keep their eyes healthy, how to make sure they have proper vision for as long as they can. What are some tips that you’d share to patients who want to keep their eyes as healthy as possible?
>> Dr. Garg: There are two things that I think would be really helpful for people. First, the same things that are good for your heart are good for your eyes. Vision requires a lot of energy. If you think about the miracle of vision, you know, we can look at something that’s light or can be dark, and our eyes can adjust to it. And we move our eyes around, and our vision remains seamless. And for that to happen, the retinal cells have to work really hard to keep sending information to the brain, and that requires a lot of nutrients and a lot of oxygen to make happen. There is a blood vessel layer called the choroid that brings oxygen and nutrients to the retinal cells, and that blood vessel layer actually gets the most amount of blood flow for any tissue for its size in the whole body. It gets more than the brain or the kidney or the heart or your muscles do. And, if you can keep that blood vessel layer healthy by eating a well-balanced diet that’s high in dark green, leafy vegetables and high in fruits and vegetables and lower in processed foods, if you can stop smoking, and if you can get moderate exercise like walking for at least 30 minutes 3 times a week, you will keep those blood vessels healthy, which then keeps your eye healthy. We also know that smoking cessation is super important. The other thing that’s really helpful, and I would say critical, is for people over the age of 40 to get a dilated eye exam by an ophthalmologist annually. The main things that can affect a person’s vision as they get older are cataracts, glaucoma, macular degeneration and diabetic eye disease. Some of those things, like cataracts, we can fix, and the other conditions, we can help protect a person’s vision. And that’s particularly true if we catch those problems early and we start treatments early. And what’s tricky about those things is patients won’t realize that those things are burying in their eyeballs unless they’re having a dilated eye exam. So I’ll encourage patients to do that starting at the age of forty.
>> Joe: Now, if someone’s interested in finding out more information about eye health, general things to look out for or some conditions, where should they go for the best information possible?
>> Dr. Garg: So, there’s a few great resources that come to mind. Merckmanuals.com is an amazing resource that has up-to-date information, both for patients as well as for other physicians. There’s a couple of other resources. The American Academy of Ophthalmology has a great website, that’s aao.org, that patients may find a lot of good useful information that’s written in a way that’s easily understandable as well.
>> Joe: And, we should of course note that for anyone who’s not in the United States or Canada, you should visit msdmanuals.com for more information. Well, Dr. Garg, thank you so much for joining us. I think it was a super enlightening conversation, and I’m sure our listeners learned a great deal about their vision health and their eye health in general. Now, before we go, as we say at the Merck Manuals…
>> Dr. Garg: …medical knowledge is power. Pass it on.