How vitamin A deficiency can affect vision
Host Amber Smith: Upstate Medical University in Syracuse, New York invites you to be The Informed Patient with the podcast that features experts from Central New York's only academic medical center. I'm your host, Amber Smith.
Vitamin A deficiency is a leading cause of blindness in underdeveloped countries. But this is also an increasing concern in developed countries, including the United States. Here with me to explain why and what can be done is Dr. Mark Breazzano. He's an assistant professor of ophthalmology and visual science at Upstate.
Welcome back to "The Informed Patient," Dr. Breazzano.
Mark Breazzano, MD: Thanks so much, Amber, for having me again.
Host Amber Smith: Now, you authored a paper about vitamin A deficiency that appears in the journal of the Royal College of Ophthalmologists, so much of what we're talking about today is covered in that paper. I'd like to start by asking how long we've known that vitamin a is linked to vision function. .
Mark Breazzano, MD: Yes, it's a great question. in terms of specifically vitamin A, a lot of that came out of work around the time of the end of World War I, so about a century, now, we've specifically linked that molecule to visual function, but knowledge of something along those lines, actually being critical for vision has been long known, as far back as the ancient Egyptians.
It was known that with a certain type of vision loss, just eating animal liver could actually restore vision in people. So we knew that there was something happening and how critical and important it was, but just wasn't isolated that, "Hey, this is the actual molecule," or the rationale and basis for that.
Host Amber Smith: So retinol is the same thing as vitamin A?
Mark Breazzano, MD: Vitamin A has a few different molecular forms, and I'm sure one of our basic science colleagues can help elaborate on this more effectively than I can, but basically there's retinol, and then there's retinol esters, basically different formations of the same compound that are essentially vitamin A, as we know it.
And then there's also carotenoids, or these other molecules that can be converted into vitamin A, for use in our bodies by our own tissues. And those are generally present in plants like carrots, spinach, those types of foods that we eat every day.
Host Amber Smith: I was going to ask -- so we can get vitamin A from our food: meats, fish, eggs, dairy, plants. Is it the same as vitamin A supplements, or is one better than the other, dietary vitamin A versus supplements?
Mark Breazzano, MD: Our meats, our dairy products, those tend to carry the more classic vitamin A component, or preformed vitamin A, as it's often called, that can be directly used for vitamin A that our body needs.
The plant-based type of vitamin A materials, or the carotenoids, like beta-carotene is most commonly known, are found in the plants. And so that needs to be converted by our bodies, depending on its bioavailability. So supplements also are prone to the bioavailability, meaning how much of it can be absorbed and then turned into the useful version of the vitamin A.
So in reality, having more of the actual component available for use is obviously critical. But at the same time, there's a certain amount that is required, and once you meet that requirement, generally speaking, superseding that amount. As I often tell patients, for many of these components in your body, you can have too much of something, just like you can have too little.
And so hypervitaminosis, also known as too much of a vitamin, can be just as bad as hypovitaminosis, or having a deficiency.
Host Amber Smith: I understand how people in developing nations might not be able to eat a good nutritious diet with adequate amounts of vitamin A. Is that what's happening in the U.S.? Are people just not eating proper diets with adequate vitamin A?
Mark Breazzano, MD: It is interesting because certain food products that you might not necessarily expect to have vitamin A actually can have a little bit of vitamin A. So it's not necessarily avoiding certain products that people may be becoming deficient in. for example, the National Institutes of Health or NIH has published a nice list of different food products that actually have vitamin A in them and among them is actually, of all things, French vanilla ice cream. (which) actually has a little bit in there because of its dairy component. It's obviously not much, but it does have some in there.
Now the issue in the developed world is, obviously, we've seen a rising trend in obesity, and along with this, there has been a need to help correct the obesity with all the other morbidities and comorbidities (one or more diseases or conditions) and other health issues that go along with it.
And so bariatric surgery has become quite popular, and with bariatric surgery, oftentimes there is a removal of tissue in the gastrointestinal tract that's important for absorbing fat-soluble vitamins, like vitamin A. And so people that have had this are at risk for having deficiencies in vitamin A, along with other fat-soluble vitamins.
And so there may be this increasing risk in increasing prevalence of people who are deficient in vitamin A as a consequence of that. Others that are at risk are those with autoimmune or inflammatory diseases, like Crohn's disease, or anything else that can affect the gastrointestinal tract. So they're particularly at risk.
So it's not necessarily what we once thought as a rare phenomenon in our part of the world, but in fact it is actually increasing.
Host Amber Smith: This is Upstate's "The Informed Patient" podcast. I'm your host, Amber Smith, talking with Dr. Mark Breazzano.
He's an ophthalmologist at Upstate, and we're talking about vitamin A deficiency and its impact on vision.
So how would a person know or suspect that they're deficient? Are there signs or symptoms to be on the lookout for?
Mark Breazzano, MD: Absolutely. One of the classic things we find on our exam is dryness of the eye, and there are certain aspects that can actually be appreciated potentially before this. So patients who have noticed a decline in their night vision, we coined this term nyctalopia, but basically a problem with seeing things in the dark and our environment effectively.
If there's been a decline, usually over weeks or months, sometimes it could be years, may be a sign of vitamin A deficiency in the right clinical context. There can be other reasons, of course, and so getting an eye exam, and particularly a dilated eye exam, will be important to help assess for that.
But usually the decrease in night vision is one of the first signs.
Host Amber Smith: But if someone came for their annual eye exam, this is something that might be picked up?
Mark Breazzano, MD: The subtle aspects of it can make it very challenging to actually diagnose. And one of the aspects of our paper that I think is particularly important and interesting is that we can use a device that's actually clinically available in many ophthalmology offices and certainly all retina offices, where basically there's an image that's used to assess the sensor part of the retina and assess for the anatomical structure there and alterations in there. And it may be one of the first signs anatomically that we can pick up, because a normal dilated eye exam may not be able to appreciate this, unless it's in its advanced stages, where you find these sort of deposits and these yellowish deposits out in the periphery, and as well as in the central macula and retina of the eye, that we may not be able to see in its earlier stages.
Host Amber Smith: Is the test you described an imaging test, or what is it called?
Mark Breazzano, MD: Yeah, it's an imaging test. It's called OCT for short, optical coherence tomography. Basically it uses light signals, collated together to produce a picture from the back of the eye. And it's become one of the mainstays for our specialty with really just visualizing the retina and really seeing it at the microscopic level that you just can't tell at either the bedside in the hospital or in the clinic at the slit lamp, the device where our face and the patient's face are right next to each other, and we're looking directly at their eyes.
Host Amber Smith: What about a blood test? Would a blood test tell you that a person is deficient with vitamin A?
Mark Breazzano, MD: Most of the time, or, I should say, much of the time, it can help detect that, where the decreased level of retinol or retinol binding protein, the actual protein that helps bind the vitamin A to get it to the places it needs to in your body, with those levels are low from a blood test, that can be very helpful for establishing a diagnosis.
The problem is, because it is a fat-soluble vitamin, it's not one that's soluble in the bloodstream or in water per se, and it's stored in the liver, that you can actually have a relatively normal blood level but still be deficient because the entire liver stores in many cases need to be depleted or near depleted before the blood level actually reaches a low enough threshold that would be picked up on that blood test.
So there are many challenges with the diagnosis. In it's more advanced forms, it's much easier to diagnose. You know, we were talking about the drying of the surface of the eye that can be picked up at the slit lamp. So once it gets to an advanced form, we can see it, but at its earlier or even moderate stages, it can be a little bit more challenging for all of these reasons.
Host Amber Smith: What is the "double carrot" sign that you write about in the paper?
Mark Breazzano, MD: A lot of clinicians, and I think particularly pathologists, or at least one of my pathology teachers while I was a medical student here at Upstate, taught us, is that they like to name things after food.
So we felt like, well, why don't we name this one after a food as well? And so basically, on the OCT image itself, right in the center, we knew that there were these outer deposits that kind of poke up and break through, a little bit, one of the outer layers there, but this type of finding, where it's sort of more horizontally placed and it has that kind of triangular appearance on both sides, we felt it was sort of reminiscent of what appeared to be a carrot, and it just happens to be that carrots people associate with vitamin A. Whether we necessarily should be or not was a different question, but since it looked like it, we felt like it was an easy way to remember among increasing number of signs and other imaging features we're finding among a lot of different retinal diseases that would be unique and memorable to the clinicians that are trying to find and assess and rule out these sorts of conditions on a routine basis in clinic. So it was more for the memorable factor, as well as the appearance on there that helped contribute to the uniqueness and robustness of the finding that we think will be helpful for the future.
Host Amber Smith: Now, you mentioned, in terms of signs and symptoms, the dryness to the eye. And I'm curious what happens to the eyes of someone without adequate levels of vitamin A and how rapidly problems might develop.
Mark Breazzano, MD: Fortunately, here we don't experience the severe effects from the dryness like we do in the developing world or underdeveloped world, in that usually if it gets to that point here, we do see the xerosis, as it's often called, basically the dryness of the conjunctiva. That's basically the translucent layer overlying the white part of the eye, or the sclera, and you can sort of see these waves and dry areas at the slit lamp. So, on real close biomicroscopic evaluation in clinic, we can see that. And if it goes untreated, usually it's not something that happens within necessarily a matter of days.
This is usually long-standing, and then it can progress to dryness of the cornea or the central, clear part of the and then, in more severe cases, you can lose other aspects and end up getting what's called keratinization, or the cells actually change what they are and they start building up with material that's not normally there something that's called metaplasia where the cell type actually changes. And eventually you can get thinning and what's often described as melting of the cornea and conjunctival structures, but this is severe, sort of end-stage, changes from vitamin A deficiency, which fortunately we do not see frequently at all in our area, but unfortunately happens with some frequency from malnutrition in other parts of the world.
Host Amber Smith: So it sounds like vision can be impacted if it's not treated.
Mark Breazzano, MD: Absolutely. And it's a different mechanism in terms of the dryness and surface changes that has to do with maintenance of the cells on the surface of the eye versus the vitamin A being used as part of the visual cycle for the photoreceptors, basically, if anyone's heard of the rods and cones of the eye, the rods, which are responsible for that dark vision, the nighttime vision, they're constantly turning over rhodopsin, which depends on vitamin A, in the back part of the retina. So two different mechanisms, but both extremely critical for the eye and for vision.
Host Amber Smith: Now in your paper, you shared some case studies of some patients, all of whom developed night blindness for several months or even a few years before this was diagnosed. Is that a typical presentation?
Mark Breazzano, MD: That is usually how this happens. And that's why whenever I hear that there is a challenge with nighttime functioning, you know, going to the bathroom at nighttime or any of these sort of night issues that weren't problematic before, and barring any other issues, like let's say increasingly dense cataracts or anything like that, that could also be causing these symptoms, I start digging a little bit more in terms of their medical history and just trying to determine what is the sort of timeline on this? It's not something that happens overnight or happens over the course of a few days. This usually happens over months and sometimes years. And one of the more tricky aspects of this as well is that oftentimes people are on vitamin supplementation or general vitamin supplementation after their surgery, bariatric surgery or gastrointestinal issues.
But the problem, again, becomes malabsorption, where they can't really absorb all of it through the supplements. And because there's been that damage, or changes to the gastrointestinal tract. And what we found is that even with normal oral supplementation, it may not be enough in many patients, and so many of us will elect to try to do the intramuscular dosage (a shot) of the vitamin, A to get that quick, high-level vitamin A supplementation to restore the levels that are stored in the liver and whatnot, and to get them to the physiologic levels that we do need.
Some of it can be a challenge though. Getting the vitamin A supplementation or getting the access to specialists who can help with assessing and administering that can also be a challenge, though, in our health care system.
Host Amber Smith: So that would be a shot, an injection, or a shot, into the arm?
Mark Breazzano, MD: It could be into the arm, but it's usually in the lower body as well, I believe, more like in the thigh or the leg, as well.
Host Amber Smith: So vitamin A can be used to treat this. Does it reverse any damage, or is the damage permanent?
Mark Breazzano, MD: Fortunately, a lot of this can be reversible, and often right after administration, within days or weeks, night vision does actually recover quite expeditiously.
So it is one of the more rewarding aspects of our field in terms of being able to treat these patients and get their vision back.
Mark Breazzano, MD: One of the interesting parts of what we found, though, was the double carrot sign corresponds, instead of the rods and night vision aspect -- the cones are part of the central vision that help with color vision -- and we found the double carrot sign actually does improve or in, in our couple of cases, does potentially resolve, but there is some delay in the functional recovery of the center of the vision.
And so that part, we do need to learn a little bit more and explore more, but the peripheral and night vision component does appear to improve or resolve quite rapidly.
Host Amber Smith: Does the normal person who has not had bariatric surgery, do they get enough vitamin A through diet if they're eating sort of a general diet, or do regular people need to be concerned about this?
Mark Breazzano, MD: I think it's fairly challenging to have a vitamin A deficiency with even our current Western diet. There are certainly many criticisms from other perspectives of the Western diet, for sure. But in terms of vitamin A deficiency, I think it is very hard for a generally healthy individual in our society today to have that. However, barring other circumstances or issues, there are other underlying problems, such as autoimmune diseases, potentially trauma or surgeries or other medical issues that are affecting the gastrointestinal tract; then, I think it's something to consider in the back of someone's mind.
But it should be quite unusual for just a regular individual who otherwise is healthy to have this happen.
Host Amber Smith: Well, this has been very informative, and I want to thank you for making time for this interview, Dr. Breazzano.
Mark Breazzano, MD: Absolutely. Thanks so much again for having me, Amber, and it's been a pleasure.
Host Amber Smith: My guest has been ophthalmologist Mark Breazzano. He's an assistant professor of ophthalmology and visual science at Upstate.
"The Informed Patient" is a podcast covering health, science and medicine, brought to you by Upstate Medical University in Syracuse, New York, and produced by Jim Howe. Find our archive of previous episodes at upstate.edu/informed.
This is your host, Amber Smith, thanking you for listening.