Vision Loss In Ultramarathons: ‘Looking’ At The Research

[Editor’s Note: Welcome to iRunFar’s new ‘Running on Science’ column, which will be authored monthly by Tracy Beth Høeg and Corrine Malcolm. The goal of ‘Running on Science’ is to interpret the established and ongoing research and theory in the field of endurance running in a way that’s not only understandable and useful for your own running, but also interesting. ‘Running on Science’ will operate in the genre of science writing. Enjoy!]

Dawn was breaking over Long Lake outside of Steamboat Springs, Colorado, when Courtney Dauwalter realized she was having trouble seeing the details of the trail ahead of her. She was leading the female race at the 2017 Run Rabbit Run 100 Mile and had only about 12 miles to the finish. She took out her contacts, wondering if they were distorting her vision. But her vision remained cloudy, and shortly thereafter she tripped and flew, hitting her head on a rock. Fluid was running down her face; she could not see the color of it, but it turned out to be blood. This was far from the last time she would fall. As she put it, “I was bitin’ the dust hard every quarter of a mile or so.”

Her vision worsened to the point she could no longer even see shadows. Her visual acuity (or lack thereof) would easily qualify as “legal blindness” to eye professionals. With just a few miles to go, Courtney used her husband as a makeshift blind guide: He verbally instructed her where to turn, lift her feet, and more. Incredibly, she ended up winning the female race, and her experience was brilliantly documented on Ultra Runner Podcast. Little did she know that, on that very same day, Mark Hammond in the men’s race had begun to lose his vision at mile 70.

Interestingly, a year prior, Chuck Radford’s experience with vision loss at the very same race was documented on the same podcast. Chuck mentioned that he was one of three runners at one aid station who had lost their vision that year(!). Their symptoms all sounded consistent with what we have come to call ultramarathon-associated visual impairment (UAVI), or as I like to say, “oooahhvee.”

Back in 2013, I flew to California from Denmark to begin navigating the uncharted territory of vision loss among ultramarathon runners with Dr. Marty Hoffman. He had, much to his surprise, noted in a survey study (Hoffman, 2011), that vision problems developed in 2.1% of 100-mile finishers and in 3.6% of non-finishers. I ran this by all the ophthalmologists in my department in Næstved, Denmark, one morning and they were both baffled and interested. One of the doctors suggested that the vision loss may be due to hypoglycemia, or blood sugar that’s too low. I doubted this, being a seasoned ultrarunner myself. After all, unless you take insulin, a runner’s (or anyone else’s) blood sugar should never go so low as to induce sustained vision loss. But honestly, I could not even wager a guess.

Marty Hoffman, Kim Corrigan, and I were able to, in a matter of just a couple months, recruit 173 people from the United States and abroad with a self-reported history of “significant visual difficulties” during an ultramarathon (Høeg, 2015). We had posted advertisements on websites and listservs and never expected to be able to study so many runners. As I read through the survey results, it became quickly apparent that nearly every single one of these runners had experienced the same constellation of symptoms, and many of them over and over again.

What exactly did they experience? Painless clouding of their vision that would get progressively worse and not go away until they stopped running.

At this point, most humanoids would have the following internal monologue: Running seems to be causing me to go blind. Maybe I should stop. But not ultramarathon runners. They keep running. This is what makes them (us) such an interesting breed to study.

And study we did, because we still did not know what was happening to the eyes.

What We Know so Far

Current Ultramarathon-Associated Vision Loss Survey Results

Here is what we were able to learn from the 173 survey participants with a total of 779 episodes of ultramarathon-associated vision loss:

  • Symptoms resolve spontaneously after cessation of running; median time to recovery was 3.5 hours and all recovered within 48 hours*
  • Bystanders tend to describe the appearance of the cornea(s) as “milky white”
  • Only 10/173 research participants had had an eye examination while they still had vision loss
  • 8/10 of those with an exam had corneal edema
  • 2/10 had a diagnosis of “contact lens irritation.” This is expected to be painful and resolves with removal of contact lenses. While contact-lens irritation should be considered in runners with vision loss wearing contact lenses, we do not consider contact-lens irritation to be the classic form of ultra-related visual impairment.

*One participant in our study reported visual issues for six to eight months following his race; however, it was not clear if the vision loss was related to the race or was indeed a case of UAVI. This participant was lost to follow-up preventing further investigation of the case.

Our study suggested that UAVI is most often a self-limited, painless clouding of the vision due to corneal edema.

What Is the Cornea and What Is Corneal Edema?

The cornea is the protective, clear, dome-shaped layer of tissue that covers the front of the eye, in front of the pupil and the lens. In corneal edema, the cornea becomes excessively filled with fluid and loses its transparency.

Cornea graphic

A graphic showing the cornea. Image: Micro Chirugia Oculare

UAVI-like corneal edema is also known to occur in long-distance cycling events. Below is a picture of a participant in the Leadville Trail 100-Mile Mountain Bike Race. Corneal edema is apparent in his left eye.

Corneal Edema in an Ultra-Distance Mountain Biker 1

Left medial corneal opacity at the finish line of a 100-mile mountain bike race. Photo: Khoadee & Torres, 2016

Corneal Edema in an Ultra-Distance Mountain Biker 2

Magnification of left medial corneal opacity at the finish line of a 100-mile mountain bike race. Photo: Khoadee & Torres, 2016

This cyclist began to experience painless loss of vision in his left eye after 93 miles of riding, which fully resolved within three days (longer than the resolution of symptoms for any participant in our running study). (Khoadee & Torres, 2016)

While I was writing this article, my friend and fellow ultramarathon physician researcher, Dr. Michael Campian, told me he had seen a photo of Mark Hammond’s eye from this year’s Run Rabbit Run 100 Mile. Mark was very kind to give me permission to use his photo and name for this article.

The below photo of Mark Hammond clearly demonstrates corneal edema in the left eye. He took this photo at the race. He developed vision loss in his left eye beginning around mile 70. “It was about four hours after I took off my sunglasses [that the cloudiness developed]. My eye didn’t hurt and the cloudiness went away a few hours after the race. The exact same thing happened at last year’s [race]. It has happened on two other occasions, and they were also times when I was running for several hours without eye protection.”

Corneal Edema in an Ultrarunner

Mark Hammond’s left-eye corneal edema at the 2017 Run Rabbit Run 100 Mile. Photo: Mark Hammond

Why Is Corneal Edema Happening at Endurance Events?

One theory is that stress to the cornea (hypoxia/altitude, cold, dehydration, debris, wind, etc.) can lead to a buildup of corneal lactate, which can act as an osmolyte in the cornea (the reverse of what happens to a cucumber when you turn it into a pickle), drawing more fluid in. The corneal acidosis from lactate buildup may further contribute to the swelling by inhibiting the cornea’s tiny pumps that push fluid out and keep our vision clear. In addition, there may be inadequate frequency of blinking. This idea came up because the blink reflex is known to be altered after refractive surgery and refractive surgery is a major risk factor for developing UAVI.

Known Risk Factors for UAVI

  1. Refractive surgery: Ultrarunners with a history of UAVI are approximately twice as likely to have had refractive surgery (such as LASIK) on their corneas than a reference group of “standard” 100-mile race registrants (p=0.001). Participants with refractive surgery were also more likely to have repeat episodes of UAVI (p=0.01). I just need to pause for a minute to acknowledge what a big finding this was. Ophthalmologists who perform refractive surgery are fond of saying this is a nearly risk-free procedure. However, if you like running ultras, this is a risk to be aware of. The reasons this procedure increases the risk of UAVI is not yet known, but may be because it disrupts the normal function and tissue of the cornea such that fluid can accumulate more easily. Alternately (as stated above), LASIK surgery has been found to interfere (by disrupting the nerves) with the normal blink reflex, thereby potentially predisposing to both corneal edema and frozen cornea (discussed later in this article).
Lasik surgery graphic

A graphic of refractive surgery. Image:

  1. Long races: The mean (±SD) distance at which visual impairment began was 45 miles. The 100-mile distance was the most common race distance in which survey participants reported vision impairment, accounting for 46.8% of episodes.

Other Variables We Analyzed

  • Running with contact lenses was not found to increase or decrease the likelihood of visual impairment
  • Visual impairment can occur across a wide range of ambient temperatures, not necessarily in the heat or cold
  • Significant wind was reported in only 23% of cases, so was far from the only cause. Also, if wind or debris were the only cause, contact lenses would be expected to prevent UAVI, but they don’t seem to.
  • Altitude (>2000 meters) was reported in only 32% of cases and the most frequent altitude UAVI occurs at is at or around sea level.

Preventive Strategies

  • Participants with repeat episodes of UAVI have frequently mentioned having success with protective eyewear.
  • I was in contact with runner Mitch Chazan in writing this article, who had numerous episodes of UAVI before trying the Wiley X Sg-1 Matte Adjustable Strap Sunglasses. Since he started using these several years ago, he has not had another episode. A nice feature of these glasses is you can switch the lenses out for no tint at night.
Wiley X sunglasses

Wiley X Men’s Sg-1 Matte Adjustable Strap Sunglasses. Image:

  • Runners have also reported success preventing UAVI with regular use of lubricating eye drops. I understand “natural tears” are more effective than “artificial tears.”
Natural Tears

An example of natural tears, for prevention of UAVI, available over the counter. Image:


  • When we published our article (Høeg, 2015), it fascinated us that none of our participants had found an effective treatment for reversing the vision loss other than stopping running and giving the eyes a chance to rest. In writing this article, I reviewed the medical literature on treatment of corneal edema and ran across the interesting idea of 5% hypertonic saline eye drops. I discussed this with Dr. Miranda Bishara, an ophthalmologist affiliated with the University of Kansas with specialty training in cornea and refractive surgery, who stated: “ophthalmic hypertonic saline drops are used frequently to help decrease corneal edema… I don’t recommend patients use them more than four times [per] day.” She recommends racers use the drops rather than the ointment as they work more quickly and do not cause additional blurring of the vision. I have started recommending runners with frequent UAVI carry a small bottle of these drops during their races (or stash a couple bottles in drop bags) to use if vision loss develops, but have yet to receive any feedback on this idea. (Please let me know if you try the drops and how effective they are!) Also, race medical personnel may consider including a bottle in their medical kit, which would not only be a potentially effective treatment but also clinch the diagnosis of corneal edema if effective.
Saline eye drops

An example of 5% saline eye drops, available over the counter. Image:

Other Potentially Exercise-Related Eye Conditions

  • Corneal abrasion is frequently suspected, though this appears to be the incorrect diagnosis, in cases of classic UAVI. That is not to say that corneal abrasions don’t happen while running. The most important distinction is that corneal abrasions are painful, while corneal edema is not. Additionally, a corneal abrasion will not look white to anyone looking at the runner’s eye. Corneal abrasions will also have a specific defect on the surface (epithelium) of the cornea that can be readily seen under a black light with yellow (fluorescein) eye drops.
  • Frozen cornea or the “Hellgate Eye” reported at the Hellgate 100k in Virginia appears to be an entirely different entity in which the cornea literally freezes in the cold. This is also known to occur in sled-dog races in Alaska. Soldiers, pilots, skiers, cyclists, ice skaters, and snowmobilers have all been reported to develop frozen cornea. This can be treated by warming the corneas, i.e. removing the cold exposure and closing the eyes. (Warming blankets and similar may also be used.) Shielding the eyes with form-fitting glasses/sunglasses or goggle-type glasses would also probably work to help prevent this by trapping body heat and keeping the corneas warmer.
  • Corneal thickness increases at high altitude and may or may not be accompanied by vision loss/distortion. This is not believed to be an exercise-induced phenomenon, but increased corneal thickness at altitude may be a risk factor for UAVI.
  • Pain or darkness in relation to vision loss is potentially dangerous and less likely to be corneal edema or classic UAVI. Other causes need to be suspected and ruled out with a prompt examination by an eye professional.
  • Persistent tunnel vision and double vision have also been reported to me in relation to running (though outside of our study set) and runners who experience either of these should be examined by an eye professional.

What to Do If Vision Loss Happens to You in an Ultra

First, I want to offer a word of reassurance. Corneal edema, frozen cornea, and superficial cornea abrasions all occur in the corneal epithelium (the top/outermost layer). This is the one layer of the cornea that can easily and quickly regenerate. Because of this regeneration, these conditions (including UAVI) do not cause permanent visual damage.

  • If this is your first episode, be sure that what you are dealing with is indeed corneal edema. Ask yourself these two questions: Is your vision whitish cloudy (and not dark) and are your eyes pain free? If your answer is “yes” to both of these questions, you are most likely dealing with UAVI from corneal edema. If your corneas appear cloudy/white (as in the photos above), the diagnosis of corneal edema is even more likely. If the answer is “no” to either of the above, you are advised to stop at an aid station for an examination by a medical professional. If you have persistent dark or painful visual impairment and the cause can not be identified at the race, you should leave the race to seek medical attention.
  • If you suspect you have ultramarathon-associated corneal edema, or have had it in the past, 5% hypertonic saline drops may be applied to the affected eye(s). My personal strategy would be to apply them as soon as the visual impairment starts.
  • If you believe you have had UAVI from corneal edema in the past, you may choose to buy protective eyewear and natural tears to use preventively. You may also consider purchasing 5% hypertonic saline drops to take along with you in case vision loss begins to develop.

Do You Have Information to Add to the Above?

  • Our research group continues to be interested in eye-examination records and/or eye photos from runners with ultramarathon-associated visual impairment (UAVI), who were examined while they still have vision loss.
  • Have you had any long-term vision or eye issues following an episode of UAVI? If so, we are interested in hearing from you.
  • If you or anyone you know ends up using 5% hypertonic saline drops to treat their UAVI, we would love to know how effective it was. I am in the process of submitting for approval a survey-based study of runners who have used 5% hypertonic saline drops to treat their UAVI. Please contact me at if you are interested in participating.


Hoffman, M.D. and Fogard, K. Factors related to successful completion of a 161-km ultramarathon. Int J Sports Physiol Perform. 2011; 6: 25–37

Høeg, T.B., Corrigan, G.K., and Hoffman, M.D. An investigation of ultramarathon-associated visual impairment. Wilderness Environ Med. 2015; 26: 200–204

Khoadee M & Torres, DR. Corneal Opacity in a Participant of a 161-km Mountain Bike Race at High Altitude. Wilderness Environ Med. 2016; 27: 274 – 276.

Tracy Beth Høeg MD, PhD

is currently a Sports and Spine Medicine physician at Mountain View Rehabilitation in Grass Valley, California, and an assistant professor at UC Davis. She completed residency in Physical Medicine and Rehabilitation at UC Davis and a PhD in Ophthalmology at The University of Copenhagen. She is a Danish-American double citizen who ran for the United States at the 2013 IAU Trail World Championships and for Denmark at the 2018 WMRA Long Distance Mountain Running Championships. She is married to Dr. Rasmus Høeg and they have two sons.

There are 82 comments

  1. Charlie

    Great article. I’ve also had issues with that, thanks for shedding some light on it. I’ll bring some eye-drops next time. Correction – Hammond didn’t drop at RRR, he came in second.

  2. Rod

    Thanks for the article. I have also dealt with this issue and could not get a cogent explanation from my MD or optometrist. I’ll try the eye drops and consider wearing preventative eyewear next time.

    1. Tracy Beth Høeg

      Great question! I doubt it is UV since a lot of runners develop this at night. It can happen at a wide range of temperatures though I have often wondered if it tends to happen with a certain change in humidity or dew point. It might be debris and wind are important factors.

  3. Brandon Heimark

    I attempted the superior 100 two weeks after lasik, didn’t go well for me. Funny thing is I went into the lasik telling them the reason for it was I didn’t want to wear glasses on long runs anymore. They though it was a great idea and shouldn’t be a issue at all. I had a drop of sweat hit my right eye at mile 3 and it instantly clouded up and was a hindrance. I spent the next 70 miles kicking rocks and roots not having any depth perception, not sweet. Then a couple hours from sunrise I noticed I was losing vision in my good eye too. Fortunately a buddy had a pacer that came across me stumbling in the night. He walked me 3 miles to the next aid station where I had to drop, 2 hours of rest and vision came back in both eyes. I did lots of personal experiments to figure it out what was happening, this was after I went back in for a check up and got the “it’s not our problem or doing” answer. Body temp, strain, nourishment and natural tears didn’t seem to make a difference. I went with windproof glasses and while it worked while they were on I couldn’t stop them from fogging up after time. Finally found some info on ultra eye and tried the cornea edema drops, used them every 10 miles and haven’t had any issues since! Thank you for this article and please get the info out there!

    1. Brandon Heimark

      If you’re having issues the drops I use are Thera tears dry eyes therapy, works instantly and if used every couple hours prevents any issues from arising.

  4. Julian Smith

    Experienced this at Nolan’s 14. Nice to have an explanation of what was going on. BTW, Eddyline Pumkin Patch Ale will remedy/help speed up recovery from this affliction too…

  5. Bethany Patterson

    I’ve had this phenomenon happen many times. I did have LASIK and have always felt that was a huge factor for me. I’ve had it several times at Hellgate, and for the record, it’s the same issue as stated in this article, not frozen corneas. The doctor as the race actually measured my eye for corneal edema one year after the race. He didn’t really notice a difference that year, but my eyes weren’t that bad that particular time. It seems to be a combination (for me) of colder, dry temps, wind, and night running. It’s been mitigated for me with eye drops and sunglasses even at night. Usually you blink less at night when you are trying to see the trail, and that definitely seems to make it worse for me. Great article! I think this explains it better than I’ve ever seen before.

  6. Aaron Shimmons

    I have suffered some of these symptoms, but it has only slowed me down – never caused a DNF. I always thought it was to do with cold or windy condition, but never dug deeper as it didn’t last too long or affect the overall outcome of a race.

    Thanks for the great article.

  7. Burke

    A few years ago I was running a race and ran up behind a guy and could tell he was in some distress. I asked him if he was okay. He said, “Yes. I just can’t see.” I asked the obvious question, “You can’t see?” He said he could “kinda” see but it was just cloudy. He was confident it would clear up. That must have between 40 and 45 miles. It must have cleared up because I saw him again between mile 90 and 95.

  8. Stephanie S.

    I do not wear contacts, but had LASIK surgery 7 years prior. I ran Lithia Loop Marathon in 2009 in Ashland, OR. It took many hours post race on a chilly fall day for the “fogging” to fade way and for me to see normally. It was as if someone had smeared Vaseline in my eyes and my vision was very much blurred. Strange.

  9. Jerry Mauney

    Had this at RRR 50 a few years back.
    started catching a toe on relatively east terrain.
    Slowed way down until next aid station.
    asked someone to look and see if I had anything in my eye.
    They thought I could be having a stroke, so packed me up and sent me to the ER.
    ER said no stroke , called an opthamoligist in .
    The eye Doc said my cornea looked like the bottom of a coca-cola bottle.
    Drops, drops, drops.
    after a few hours started seeing better.
    Comming off a fairly recent traumatic brain injury I have assumed the eye was a result of my head injury.
    Thanks for the knowledge that others also have suffered this aggravation, without getting their head wacked.


  10. Henry Lupton

    I’ve been having this problem ever since I started running ultras. Never had a name for it. How would I join any studies? Btw, I’ve never had lasik, but I do have moderate/severe glaucoma. Time to clear up is usually 4-8 hours. Never any pain.

    1. Tracy Beth Høeg

      Great idea, Pete. I actually just mentioned this above. I suspect it may play a role given a lot of runners develop this as the sun is coming up. I haven’t looked at this in a systematic way though. Why do you ask? Do you have a theory about the possible mechanism?

      1. Pete

        Hi Tracy- Thanks for the response! My question about humidity is partly motivated by my own experience with maybe something like this — cloudy, blurry vision that developed after running all night one time visiting the Phoenix area, in bone-dry conditions that I was not used to; and, partly by your picture of the strap sunglasses found by some to be effective at preventing the condition. Thinking about why those glasses might help, I am guessing from the picture that they might trap humid air by the eyes and mitigate drying – which would be more a problem in low humidity. (… & running all night in dry Arizona air I wasn’t wearing sunglasses!) Again, great article!

  11. Jeff Hart

    At the 2016 Wasatch 100 I had my first bought that was bad enough I literally ran passed the finish chute. I used drops but “saw” little of any relief. I felt the dust and glare from my headlamp off the dust aggravated (perhaps led to the onset) of the clouding.

    At Hardrock 100 this year I started to have issues but with an hour of rest they more or less resolved.

    For me intensity of effort seemed to play a role.

  12. Steph Jeffries

    Great article; I’ve had this happen to me in distances marathon and above, but not every time. Seems like drying is a factor. Sometimes the cloudy vision starts after the end of the run. It is always gone by the next day. I always carry eye drops (can’t remember what kind). I have had LASIK and haven’t had any other side effects. Once my eyes cloud up, eye drops help, but only temporarily (I have to reapply them every 20-30 minutes). Sometimes my eyes are a little goopy along with the cloudy vision. Have not noticed the obviously cloudy corneas as photographs in the article show.

  13. Christopher Lee Culpepper

    Great article. I’ve had issues the last two Rocky Raccoon races. I used drops(Systane Ultra) for this years race but my eyes started to go south around mile 30. It takes about 3.5 to 4 hrs for my eyes to clear-up. I even tried to take a two hour nap to see if they would clear and didn’t have any luck. I finally purchased some prescription goggles similar to what are shown in your article. No problems with a recent 50 miler but still need to try them at 100 miles. Yes. I’ve had Lasik and wore contacts for a very long time before getting surgery. I have a 100 miler next week at Javelina. Hopefully this problem can be managed. Off to Amazon to get some drops.

    1. Christopher Lee Culpepper

      Just a follow-up. I ran my first 100 miler with the goggles and didn’t have any eye issues until mile 90 when my right eye developed some cloudiness. This was much less extreme than previous episodes. The temps had cooled down significantly prior to this, ~ 57F, and wind was getting under one side of my goggles. I used the sodium chloride drops and this seemed to clear up the cloudiness temporarily. I consider this a win.

      1. Tracy Beth Høeg

        That is really great to hear, Christopher. My impression is the goggle type glasses are very effective for most people. And I am glad to hear the sodium chloride even worked a little. You are actually the first person who told me they might have worked. Cool. Thanks for the follow-up!

  14. Lee Chu

    Excellent article. I’ve had classic UAVI at 50 K/mi races. I also have had UAVI at the Seattle Marathon several times so marathon distance runners may be another source of information.

  15. Maggatron

    This has happened to me. In 2014, at Gorges Waterfall. Probably around mile 45. Interesting that was called out as the beginning mileage for this issue to occur. For years, I have always wondered what caused it. Noticed it one more time towards then of a 50 miler 2 months later and hasn’t happened since. Knock on wood. But yeah for about 4 hours after GW I couldn’t see a thing but gradually improved after. So crazy all this has surfaced since Courtney’s epic RRR. Good to be paying attention to. Thanks for writing this, Tracy and let me know if I can help.

  16. Bob Clouston

    I had one eye affected last year at Tunnel Hill from mile 50 on. It didn’t get much worse through the night and with one good eye I wasn’t really impaired. I was thinking Hellgate Eye and tried to wrap a balaclava around my eyes as much as possible to keep the area warm. Luckily I knew from people like Bethany that it wasn’t permanent so I didn’t panic. After about 3 hours sitting inside post-race, it cleared up. It was cold (low in 20s) but I think it started before it dropped below freezing, and it wasn’t windy. My previous 100 was a bit colder but no issues, and that race went generally worse for me. I had LASIK done about 15 years ago. Good article!

  17. Todd M Nickel

    This is an interesting article, and extremely well written and researched. I am an ophthalmologist and perform LASIK and other eye surgeries, it is quite intriguing to read about this phenomenon.

    I have a few initial thoughts, which I would like to share. This morning, I have also shared this article with a few of my colleagues across the country, and we have posted this article on an international ophthalmology forum. So, in a couple of days I will attempt to summarize all (most) of the thoughts I can accumulate and hopefully we can add to this research initiative. This is an interesting and confounding problem, Ultra Runners will be thankful for the good work done by Ms Hoeg.

    *First of all, the differentiation between “artificial tears” and “natural tears” is more of a marketing and packaging nuance. I don’t believe there are (good) studies that show one to be “more effective” than the other. There is a difference between “preservative free tears” and artificial tears/natural tears with preservatives. The CVS tears pictured are “preservative free.” When using lubricating drops, if you are going to use the drops/tears more than 4-6 times a day, especially multiple times during an ultra race, I would recommend preservative-free tears. They come in individual vials, and can be kept easily in packs and pockets.

    *Corneal edema can be painful. When the cornea becomes significantly edematous, bullae (little cysts) can form on the surface and may be uncomfortable or painful. When the corneal epithelium is “roughed up” enough to cause edema, especially if dry eyes are implicated, the eye can have significant burning and stinging, even pain like a scratch on the eye. So, the absence of pain in these folks points (possibly ?) to a disrupted mechanism of the deeper layers in the cornea.

    *Early in the post-op period, LASIK contributes to decreased corneal sensation, and a decrease in tear production, thus dry eyes. Most patients will improve to be asymptomatic by one year. Prior to LASIK, if a patient has significant dry eye symptoms, often we will maximize tear production with medicines, drops and even autologous tears, and if the symptoms are difficult to relieve or manage then we usually recommend photorefractive keratectomy, or no treatment.

    *While sodium chloride solution is typically recommended to be used 4 times a day, it can be used as much as tolerated. If it is helpful to clear the vision, the benefit may be short-lived. Thus, many patients utilize these drops multiple times a day. Sodium Chloride is most helpful when the cause of edema is endothelium-related, but is not a cure. If the pathology is dry eye or abrasions, epithelial-related, this sodium chloride solution will likely burn and sting and may not be found to be helpful.

    *The protective glasses/goggles would be used to protect the corneal surface from exposure to wind, and excessive drying. Like a windshield in your car vs driving a motorcycle without glasses.

    *Hypertonic saline drops work to (basically) draw fluid (edema) from the cornea to decrease edema and clear the cornea , temporarilly. Artificial tears/natural tears simply lubricate the cornea to clear up the cornea-tear interface making vision clear. Both could work, but really depends on the mechanism of the corneal edema.

    The pictures show clearly that the problem is corneal edema. The cornea is made up of five layers: the (1) superficial, outside, layer, is the epithelium,the barrier layer and is similar to skin on the body. The epithelium protects the cornea, contributes to much to the clarity of normal vision. Directly beneath the epithelium is a very thin layer of a (2) basement membrane, (Bowman’s layer) The (3) inner, thickest, layer of the cornea is the stroma. The stroma is what becomes abnormal, and opaque, when the cornea has edema, (although the epithelium can also become slightly edematous.) The fourth layer (4) is Descemet’s layer/membrane. And then the (5) inner-most layer is the endothelium, this layer is the bottom layer, exposed to the inside of the eye. The endothelium is the “pump-cell” layer. Its job is to keep the cornea clear, not opaque. It is made up of a sheet of thousands of cells that pump fluid from the cornea.

    Corneal edema occurs because of three main factors: 1. Epithelial (outer) layer barrier disruption. When the epithelium is altered, the entire fluid composition of the cornea can change, and become altered in its clarity, due to edema. 2. Endothelial layer malfunction, when the cells stop or slow down on their job of pumping fluid out of the cornea this allows the cornea to swell and become opaque. 3. Increased intraocular pressure (IOP).

    The reasons for these factors could be the following: (and, of course, this is not an exhaustive list.)
    Epithelial causes for contributing to edema could be related to abrasions, erosions, dryness ( really, this is micro abrasions/erosions), chronic exposure, chemical injury and thermal injury. Though dry eye could be contributory to this phenomenon, it is relatively underreported to have this effect in other scenarios/patients and we see a fair amount of significant Dry Eye Disease (DED) in our practice. DED resulting in corneal edema is rare. The same is true about the other potential causes, rare (though possible) to see corneal edema in these scenarios except with significant infection, trauma, and or chemical or thermal damage.
    Endothelial (pumping cells) dysfunction would be the most likely cause for this type of edema, and as I have received responses back from three of my (highly experienced eye docs- think, like the Karl Meltzer or Scott Jurek, Meghan Hicks or Bryon Powell of ophthalmologists) colleagues already, all three have focused on the possibilities of endothelial damage/malfunction. Each of us generally believe that although the underlying trigger may be unknown, the mechanical problem likely lies in the endothelial pumping problem brought on by running many miles. Somehow. The main causes for endothelial dysfunction are: trauma (usually has to be bad enough to tear the membrane), infection, toxicity, systemic medicines (rare), hypoxia, dystrophies and dysgeneses (though dystrophies in this patient subset would be hard to imagine given the relative young age and excellent health), and immune mediated.
    Increased Intraocular Pressure. As pressure increases, endothelial cell function decreases and the cornea becomes edematous.

    I am fascinated with this report. Here are a couple of notes which may be helpful in determining a cause.

    A few brief ideas so far from me and colleagues: 1. Increased intrathoracic pressure which could increase IOP, which could slowly alter normal endothelial pump function resulting in edema. 2. A postulate regarding the prolonged bounding (bouncing) which may alter convection currents of the fluid in the eye which could (?) alter the endothelial pumping cells. 3 Pigment dispersion, due to bouncing and pigment being released from the iris, which can lead to increased IOP. 4. Altered chemical composition systemically, which could (?) alter the function of the pumping cells, leading to edema.

    A couple more thoughts on follow up. Intraocular pressure (IOP) should be measured in these runners. Somehow, I would love to see a study (or added to this research) to measure the IOP on these UAVI athletes. If the IOP is high, then a anti-hypertensive medicated eyedrop may be effective at reducing edema. Also, an immediate slit lamp exam could/should be done on these UAVI folks after they cross the finish line. Much could be learned by looking closely at the cornea, the LASIK flap, the anterior chamber and more. Follow ups with ophthalmologists to examine the entire eye, including the cornea’s cell count and morphology would be helpful in determining some identifying factors for these runners.

    Meghan and Bryon, I would be happy to join y’all at a big race to do some testing some time!

    Great work! Great article.

    1. Brandon Heimark

      My experience with it started 2 weeks after lasik, I tried the anti swelling drops and the lubricating drops with zero change. After rest my vision came back. Next race I kept my body temp lower, made sure to keep nutrition up and took excedrin thinking it was head swelling/pressure on the back of the eyes. Nothing I did helped until my next race I wore wind proof glasses, after 50 miles I got tired of them fogging up so I took them off and started to lose vision a hour later. Put them back on and it didn’t get worse. After reading about cornea edema I bought some drops with sodium chloride, next race was night and day. Once I started to get a little cloudy I started drops, cleared up within minutes and drops every 10 miles now leaves my eyes perfect without having to wear the windproof glasses.

      1. Tracy Beth Høeg

        Brandon, that is great to know about your experience with the sodium chloride drops. I would love to ask you some more questions about this. Could we discuss over email? If you don’t want to write your email address here, could you possibly write me at

    2. Sara Bozorg

      Hi Todd- great review of possible pathophysiology- im a cornea specialist out in NH- would also be available to help testing if anyone wants to set up a 100mile race specifically as a study!

    3. Tracy Beth Høeg

      Thank you Dr. Nickel for your excellent points and observations! I would also love to arrange testing of runners at a race some time. Please let’s try to coordinate it & obtain IRB approval (I think Run Rabbit Run would be an ideal race to target). Only since it would matter for our potential study together, I am actually “Dr. Høeg” (MD, PhD) and not “Ms. Høeg” ;-). Please email me if you are interested in setting up a study:

      1. Todd Nickel

        so sorry Dr. Hoeg…for some reason I couldn’t tell when I (briefly) looked at your by-line that you were a doctor! I apologize! you do have a LOT of letters after your name and certainly missed that!

        It would be a really cool study, especially if an ophthalmologist or two could examine all the UAVI AND non-UAVI runners in a race. I think the eye exam would be pretty simple, if you had good examiners who could adhere to guidelines. It could be a fairly easy process. The IOP really needs to be measured, the cornea needs to be evaluated systematically, looking for epithelial (fluorescein would be helpful to see epi changes and would anesthetize the eye for the IOP check) and purely stromal, and endothelial causes. Pigment dispersion could be seen pretty easily on this exam as could any frank epithelial changes.

        It is difficult for me to imagine that the wind, exposure, dust etc. would put the corneal cells under a strain any greater than many corneas/patients we see with exposure issues (due to eyelid problems, trauma, scarring etc.) or neurotrophic changes ( HSV keratopathy etc.) and these corneas don’t swell. Their epithelium may look ragged or develop ulcers, but exposure alone doesn’t typically cause edema.

        Another cornea specialist responded last night with an interesting take which was that he noticed that in the pictures you show, the edema starts peripherally. This is where corneal circulation is greatest and where the cornea would be exposed to the highest levels of lactate in the blood, especially when the athlete was having difficulty clearing lactate! (I’m no scientist, but this is at least real anatomy and physiology)

        If this is the case, that it is in fact initially peripheral and/or concentric edema, then that observation could be seen in a post-race or intra-race exam. However, these patients could/should also have a blood draw to determine lactate levels. So, possibly. this phenomenon may not happen to runners/athletes who are more efficient at clearing lactate!? Nevertheless, once the cornea surpasses its ability to clear the lactate, it could have an imbalance and start to swell. But because the epithelium is OK (though it may be dry or micro-abraded) and the pump cells are (presumably) ok, then once the body starts to clear lactate from the blood stream/cornea etc. the edema goes away!? possibly.

        One of my partners, wondered about IOP and mused that if something was causing mild inflammation of the ciliary body that it would be possible to get endotheliitis, which causes swelling in the iridocorneal angle, which could cause a chronic and partial angle closure glaucoma episode, with resultant increased IOP and edema.

        Also,my guess (only a guess at this point) is that the LASIK flap has little to do with this, especially if all of these episodes are SIMILAR in the edema seen. However, if the flap causes a unique reservoir for fluid accumulation, then it might be that we recommend PRK, instead of LASIK, for these folks in the future, and this study could be quite instrumental in our guidance to patients. However, I perform cataract surgery all the time on folks who have had previous LASIK, and when they develop corneal edema in the postoperative period, I don’t see more edema in those with LASIK flaps, or any specific flap-related lamellar changes, and I have looked for this over the years.

        All that to say, I had no idea this was happening but I continue to be fascinated.

        Again, Doctor Hoeg, thanks for your work, let me know what is next! I would love to help.

        1. Tracy Beth Høeg

          Todd, and please do call me Tracy! The “Dr.” comment was just clear up my educational background since I truly hope we can collaborate for a study. I have actually been at Western States doing research the last four years (also of other factors related to ultramarathon running) ready to measure intraocular pressure, use fluorescein and measure corneal thickness as well as perform a general eye exam but NO ONE has had vision loss! Ugh! ;-)

          I am very intrigued by the lactate theory related to the peripheral cornea as it could explain why these episodes seem to be related to both intensity and exposure. The idea of pigment dispersion syndrome and/or increase intraocular pressure also interest me. Of note, our research group did a study that I just submitted for publication that found ultrarunners who did NOT lose their vision had a slight but not significant DROP in their IOP from start to finish of the race. A drop in IOP is of course expected with exercise, though I am not entirely sure WHY that happens. Perhaps it is even a protective mechanism against UAVI!

          It would be amazing if we could arrange a study in a place where there are enough runners lose their vision that we are able get to the bottom of this fascinating phenomenon. I will write you now about setting this up. I already got a very high recommendation of you from Ms. Meghan Hicks. I look forward to collaborating with you! Cheers! And thank you for all of the amazing insight and for including your colleagues’ interesting theories.

        2. Jackie Lai

          Well, I had LASIK in my right eye, and PRK in my left eye due to a scar on the left cornea. The scar is from a procedure to remove sand that was in my cornea. Going to the beach, wearing hard contact lenses and being 12 years old don’t mix together well! If I ever get vision loss while running I will get an eye exam and let you know the results.

  18. Jeff Hubeli

    Thank you, thank you! It’s not just me! I experienced UAVI during a 50 miler last year, TNF EC CA, and literally stumbled my way to the finish. Condition cleared up a couple hours after finishing. I have not had LASIK but do have glaucoma. In your analysis has that been found to be a factor?

  19. Don

    2013 Ironman Coeur d’Alene in Idaho I completed my first Triathlon. The last 1/2 mile or so is downhill on a straight road, i turned the corner and sped up. I lost all of my vision but since the road is lined by cheering people I just kept myself in the center of the road, i had volunteered at the race every year since 2009, so I knew what the route was. The last 100 yards is a carpet with a 10′ wide chute that you run down, at that point I could see about 10 feet in front of me. I assumed it was due to dehydration, but I never asked anyone professionally about it.

  20. Robert Cykiert, M.D.

    Can’t think of any mechanism of how running would damage the corneal endothelium resulting in corneal edema, especially since it only lasts a few hours, and appears to be unilateral in some people. Also, no mechanism for primary stromal edema. Therefore 2 possibilities remain:

    1. Epithelial edema and SPK (superficial punctate keratitis) from exposure: wind, dust, etc., or more likely sweat pouring into eye for hours. I’ve had many long runs where my sweat gets into the eye repeatedly and burns and stings and occasionally causes transient mild blur which requires frequent blinking to clear. If you’re running an hour or two, no big deal. If you’re running 100 miles, it’s cumulative corneal epithelial toxicity and epithelial edema. After a few hours that resolves. I’ve also experienced worse symptoms if I run in the summer, put sunscreen on my forehead and then sweat carrying sunscreen into my eye. It burns real bad. I’ve experienced even worse symptoms if I wear a contact lens and get sweat mixed with sunscreen residue.

    2. Some of these people may have Pigment Dispersion Syndrome and/or Pigmentary Glaucoma and get transient elevated high eye pressures from the jarring of a 100 mile run. The run releases pigment from the iris which clogs the trabecular meshwork of the eye and causes high pressure which can cause transient corneal edema. Here’s some articles on this topic. and A short run may not cause high pressures, but 100 miles may.

    I suggest that runners who experience this symptom have their eyes examined by an ophthalmologist; if possible during the blurry vision episode. If you can’t get an exam while blurry, see an ophthalmologist to rule out pigment dispersion syndrome and/or pigmentary glaucoma.

    1. Tracy Beth Høeg

      Dr. Cykiert, Thank you for these excellent points. I have been wondering about the possibility of pigment dispersion syndrome contributing to the corneal edema (since it is known to happen with vigorous exercise!) and, that it is likely combining with SPK from exposure makes complete sense to me (perhaps why protective eyewear and lubricating drops help prevent it). I 100% agree that runners who experience symptoms should try to get an exam by an ophthalmologist while the symptoms persist (an exam which looks into the above mentioned conditions and checks intraocular pressure) so that we can begin to get to the true cause of this condition.

      Please anyone with examination records from an ophthalmologist that could help shed light on the above theories, I would love to hear from you (again: Cheers! And thanks again, Dr. Cykiert!!

  21. Bethany Patterson

    Nick, thank you for your post. The suggestion about the drops will definitely be something I try in the future. I did have my eyes tested after finishing a 100K once. Not sure what the test was called, but I believe it was measuring pressure. They pushed a little thing against my eye several times to measure the pressure? Does that sound right? They put some numbing drops in first. They then retested about 3 hours later to see if there was a change, and also if there was a difference between my bad eye and good eye. There weren’t any good conclusions from that one test, but my eyes weren’t that bad that particular time. It does seem to happen to me more in colder and drier races more than warmer ones. It can happen as early as 5-10 miles into a race. I have had some scratchiness at times, like sand in your eye, but not exactly painful. I also have chronically dry eyes, which definitely doesn’t help matters. Thank you for someone finally writing this article and for all of those who have chimes in. This is usually my biggest concern before a race, so to have a solution would be wonderful.

  22. Allan Couch

    Since this does appear to be corneal edema, wouldn’t you need to make sure you correct the IOP for the thickening of the cornea? I’m a retina doc so you corneal folks may be shaking your head at this question, but just a thought if you all do put together a study. Thanks.

    Also, great article. I always read most medical related articles, in sports magazines, with skepticism but this one was excellent. The comments have also been very enlightening.

    1. Tracy Beth Høeg

      Thanks, Dr. Couch. Good point about the corneal thickness and IOP. Of course anyone measuring the pressure in the eyes of these runners would need to take that into consideration. Unfortunately there is not really an accepted formula for this, but if the corneas are quite thick, a little elevation in the IOP is probably within normal.

  23. BB

    I saw mention of blood sugar but no mention of salt/electrolyte imbalance, which strikes me as a massively likely variable. Basically a hyponatremic situation in the eye affecting relative osmotic pressure across the eye.

    I have improved my vision immediately under fatigue with more salt and slight hyperventilation (Wim Hof method).

  24. Charlie Alewine

    Hi Tracy,

    I lost vision three times during races and have permanent vision loss. Two of the incidents happened during 100 mile runs. In one race, I lost vision in one eye at around mile 20 on Saturday, but finished the last 80 miles by Sunday morning. My vision didn’t return for two weeks. My opthamologist had told me I may not get it back at all.

    I’d like to give you my input if you’d like. I was amazed to read this article and relate, yet my VA opthamologists never mentioned wind problems. That’s exactly what originally caused the problems, along with being too stupid to quit running when I experienced vision loss during races.


    Charlie Alewine

    1. Tracy Beth Høeg

      Charlie, two weeks is a long time. Was your eye painful? Any chance you got a corneal abrasion from debris in the wind?

  25. Ben Rogers

    Really interesting as when I was doing my “marathon a day” for a year, I also had this issue early on in my challenge…
    Clearly I was not doing ultra distance, but was doing daily high mileage.
    I only had it happen about 5 times in the first three months, but found that when I finished my run, I would definitely be lacking vision. I found that when I had been sitting in the bath for about 20 minutes, my eyesight would return to normal. I don’t wear contacts and have not had eye surgery, but do wear glasses (although not for running).
    It is good to know that this is not an issue for long term sight damage as my wife was worried. Also as I did not find anyone else suffering from the same thing, it is good to know that I am not the only one!
    I have not had the issue for many months now, but am increasing my race distances into 100k/100M runs, so will keep an eye on it (no pun intended) and see if it comes back in the longer runs…
    Thanks for a great article

  26. Dave Essinger

    Fascinating stuff! Sounds a little like my experience, a little different. One year, at night at the Mohican 100, I started experiencing, not clouded vision, but tunnel vision, a closing-in of my peripheral vision when I tried to run, that quickly resolved when I’d slow down and walk, but immediately returned on stronger effort. Not sure the cause, and hasn’t happened since under similar conditions, but I’m glad to know someone’s researching this–and that I’m not the only one who would keep running with such weird issues!

    1. Tracy Beth Høeg

      Definitely sounds different, Dave. Was it both eyes? Might be worth getting a full eye exam to check visual fields and intraocular pressure just in case, if you have not done this already.

  27. Pete Kirkham

    I’ve been dealing with this phenomena for almost 30 years in both eyes. This is the first article I have found dealing with this topic, THANK YOU!!! I thought I was the only person on planet Earth dealing with this problem. Most of the time for me it’s been a minor problem but the first time it happened 25 years ago, on my first Grand Canyon R2R, I had to stagger out practically blind, very scary! The last bad bout I had a few years ago was on a solo one-day jaunt on the 44 mile Rae Lakes loop in the High Sierra, where almost total blindness hit me over the last 8-10 miles of mainly rocky downhill at sunset…not a great combo!!??
    I have noticeed a correlation between effort and time….the harder I’ve run/hiked and the longer I’ve done it seem to bring on the symptoms in either one or both eyes. For 4-5 hr efforts I’ve noticed it only hits me after I’ve finished and within 2-3 hrs it’s resolved itself. Running/mtn. hiking seems to bring it on with more frequency than does long-distance mountain biking, at least for me. I have never done a 100 mile ultra mainly for this reason!!!
    It will be interesting to see where research takes this phenomena as I will definitely be using the eye drops you recommend in the future…..thanks!!!

    1. Tracy Beth Høeg

      Pete, sorry about your struggles with this. I am glad you found the article helpful. Please, if you get a chance, let me know if the saline drops work for you!

  28. Monica Alas

    Wow, this article and comments have been super insightful! Ha! I am yet another utlrarunner that had this happen during a 100-mile run. Mine was the Leadville Trail 100…similar elevation to RRR. Mine occurred in only the left eye and started around mile 30 and worsened as the mileage ticked by. I did use drops (OTC Systane eye drops) often afterwards and my vision came back after about 24 hours or so. I thought it had to do with a hemangeoma (sp?) that I discovered a couple of years ago which pressed against my optic nerve and caused vision loss. A quick bout of radiation shrunk the mass just enough to relieve the pressure and I regained the lost vision, thankfully. I assumed this was related to that issue since it occurred in the same eye. Since my eyesight came back so quickly, I have procrastinated seeing my eye dr. until now. My appt. is next week. I’ll be sharing this great info. Thanks again.

  29. Jim Grindley

    Two different years when running the LeGrizz 50 miler, I had blurred vision in one eye by the end of the race. Each time there were obvious red blood cells in the anterior chamber of the eye. The first time a family physcian made the diagnosis of red cells and I could see it myself when looking in the mirror. Vision was back to normal by the next morning. Opthamologist exam showed the eye was compketely back to normal two days later. I have run this 18 other times, Leadville 100, Western States and many other mountain trail races without any problems. Both times it was my left eye.

  30. Sean Stone

    Tracy, I’ve mailed you a brief note relating to our recent experiences of this problem in the longer Scottish ultra events. I encounter a reasonable sized sample of cloudy eye cases each year in my role as finish line medic and have been following your discussions for some time. I suspect that the atmospheric conditions at our events are perhaps a little different to many of those in the continental US but still we find a noteable percentage of runners will develop this in (say) 40 mile plus races. I very much support what you are doing and think that if we can reduce the incidence and severity of cases, we can certainly reduce the number of DNFs in our longer races along with also giving me less trauma to manage!

    1. Tracy Beth Høeg

      Oh, yes, of course I remember you. Thanks for getting back in touch. A couple thoughts: do you have any ophthalmology or optometry contacts in your area or somewhat close to the finish who could either do finish line exams or have the runners referred to their office if they do lose their vision? This is something that would need to be set up ahead of time since these races usually finish on weekends and nothing is open! I will include you in an email list we are starting to develop guidelines of how to best examine for this phenomenon in remote areas.

      If nothing else, take a picture of the eyes and then apply the 5% saline drops to see if the vision clears up.

      1. Sean Stone

        After our last discussion, I had arranged for an opthalmic consultant to attend our busiest finish line of the race season but unfortunately this was cancelled at the last minute on that occasion. I will try again for a similar arrangement for April 2018 but in the meantime, would be delighted to receive advice on examination and application of hypertonic saline where indicated. As these things tend to be in this country, our busiest finish line, the Highland Fling, is nearly two hours from the nearest definitive care. I’d really like to be able to manage cases ourselves wherever it is sensible to do so.
        What I could probably also do is prepare a couple of the more experienced volunteers to do a simple screening of 100% of finishers, so that we can get some basic numbers together- that way we get a rate of presentation and some description of atmospherics for context.
        The longest event in the Scottish calendar is the West Highland Way race at 95 miles in June; at least there, our 200 runners have an ER 400 yards from the finish line.

        1. Tracy Beth Høeg

          I think the easiest thing to do at a finish line would be use a tonopen to measure pressure in each eye, take a photo focused on the corneas and then use fluorescein drops with a black light to see if there are any abrasions. If you can get your hands on a pachymeter, too, that would be helpful. Those are all quite portable. Bummer the ophthalmic consultant couldn’t come! Would be great if he/she could be there in April. Show him or her the article and perhaps they will be more interested since it is still a bit of a mystery what is going on. Even though I have already gotten some feedback that hypertonic saline drops have NOT worked, they may still be worth a try.

  31. David Lockyer

    Interesting article. I suffered vision loss at about mile 60 of a 100 mile winter coastal ultra here in the UK but my symptoms seemed different to what has been discussed here. I found myself with severely blurred vision and felt like there were ‘salts’ in my eyes. I was unable to read a map or the display on my GPS watch. I had the medics flush them at mile 80 and continued but there was no improvement. The whites of my eyes turned red. Someone at the finish suggested it was possibly related to electrolytes and someone else that it may have been salt blowing in from the ocean. I fully recovered within 24 hours. Some weeks later I suffered a similar experience with more of a double vision issue on a long low carb bike ride.

  32. Pete Kirkham

    I just completed the Flagstaff Fearsome 4 Challenge in AZ this past weekend. After climbing the first two peaks on Friday with 6233′ elev gain in 20 miles in 6 hrs 17′ I started to get the typical ‘glazing’ over of my right eye that I have been accustomed to after finishing a long distance event. I put a drop of the 2% Sodium Chloride drops in each eye and it almost instantaneously cleared up 95% of the clouding. This is the first time that I have used them since reading your article a couple of weeks ago.
    I will keep you posted on future events…

    1. Tracy Beth Høeg

      Pete, that is great! Thanks for letting me (us) know. I am curious if you really used 2% sodium chloride rather than the 5% mentioned in the article or if that was a typo. How much further were you able to run after you applied the drops?

  33. Anna M

    I’m wondering if cold has something to do with this? I recently did a 50K and felt my vision cloud up after around 18 miles. Very hard to focus on the trail. The race temperature was in the 20s. It cleared up when I sat in a warm tent and ate and drank. A few hours later I had a bit of a headache for a short while.

  34. Tracy Beth Høeg

    Anna, sounds like it might have been frozen cornea if you mean 20F. We found UAVI could happen at just about any temperature and did not appear to be significantly correlated with colder temps. My impression is that frozen cornea and UAVI are two distinct problems (though there may be a relation that I am just not aware of). Did anyone take a picture of your eye? That would be a good way to tell.

  35. Jonnifer Lacanlale

    I have had the same problem in 2012 during Western States 100 but I did manage to finish the race … barely few minutes to cut off. I remember vividly that the doctor during the race did not know what was happening and could not provide a quick cure.

    I also participated in this Vision Loss study after the race. Thank you so much Tracy and your Team for this!


  36. Culley Smith

    I had a similar experience yesterday during the 2018 Frozen Otter 100K.

    I had LASIK performed on both of my eyes in February 2016. I noticed that my eyes, especially my left, were susceptible to dryness and clouding of vision during long cold winter runs. I started keeping single use eye drops (used post surgery) in my car to clear my eyes out.

    Around 34 miles into my 100K, my vision started blurring. At mile 37, while at an aid station, I applied eye drops, but it made my eyes much worse. By mile 45, I could barely see. I tried splashing warm water in my eyes at that aid station. It helped, but minimally. I went on to mile 55 and dropped. About 9 miles from the finish (it was a 64 mile race). It was dark, in the woods, and my headlamp made for a “high beams in fog” effect where I could not differentiate any details. I was stumbling, falling, and crawling along the ground on my hands and knees trying to stay on the trail.

    This was a winter race in Wisconsin where temperatures dipped to -10F with the wind chill. While I should have been smart enough to wear goggles or a mask, it just never occurred to me. I had made other plans for safety and comfort, but having trained all winter (and having done a 50K in similar conditions the previous winter with only light drying of my eyes), I overlooked this as a possibility.

    My eyes are a little dry and scratchy some 12 hours later, but the clouding disappeared after about 4 or 5 hours of sleep.

  37. Richard

    Haven’t read all the reply’s, but could this be an electrolyte issue?

    This from wiki
    “The corneal endothelium then transports water from the stromal-facing surface to the aqueous-facing surface by an interrelated series of active and passive ion exchangers. Critical to this energy-driven process is the role of Na+/K+ATPase and carbonic anhydrase. Bicarbonate ions formed by the action of carbonic anhydrase are translocated across the cell membrane, allowing water to passively follow.”

    Were there any other symptoms of electrolyte depletion?

  38. David Fuller

    Thanks much for this article! I posted the message below Oct 2013 after reading the IRunFar article ‘Your Ultra-Training Bag Of Tricks: Troubleshooting On The Run, Part One:’ by Ian Torrence:


    DavidF October 7, 2013 at 2:50 pm
    Some might be interested in eyecare — in this case Cloudy Eyes. 4 racers were affected with it at the 2013 Bear 100 and I believe 3 of 4 had to drop. I was a lucky finisher. Maybe this experience will help any other ultra-runners who have been affected and/or want to prevent it.

    I’ve had a little bit of ‘cloudy eye syndrome’ on some of my cold morning long runs but it was minimal and it cleared up after getting in a warmer place and out of the wind. At the Bear 100 in 2013 it was quite cold for most of the 100 miles. At about mile 30 one of my eyes started getting a little blurry. By mile 45 both eyes were affected. When it got colder and the trail moved in higher/more exposed conditions it got progressively worse. Luckily when it was just me on the trail with a headlamp light pointing in front of me I could make out the key details of the trail. It was slow picking at times but it worked.

    Wherever snow covered the ground though the light became diffused and just like fog it made for harder discernment of objects. Aid stations were especially bad with car headlights and propane lanterns. I could hardly see there and had to be shown where food was and what it was. So I tried to warm my eyes a little at aid stations for 10 mins or so but got anxious to get back on the trail.

    By sunrise I was in high elevation, cold conditions, 100% cloud cover and snow-covered ground. I could hardly make out the trail in spots and almost stopped to wait for other runners for me to follow. But I plowed ahead, fortunately found the trail markings and slowly picked my way through the rockier and snow-covered sections. At mile 85 I decided to try a new strategy. I borrowed some semi-wrap-around sunglasses from an aid station worker and then spent 15 mins warming my eyes over a propane heater. Then I hit the trail and shielded my face from any side wind and kept my Buff over my mouth so extra breath moisture would rise up into my eyes. After about an hour my vision improved some. In another hour it was even better. The temperature that day also went up from the day before. By the time I was making the final descent to the finish my eyes were I would guess at 90% clear.

    So after talking to my retinal surgeon brother, here are some things to consider for next time.

    1. Hydration – I was well hydrated and peeing lots. Dr. said that even with good hydration the eyes get fluid secondary to vital organs. So under heavy exertion conditions the eyes can dry out which in cold conditions can result in cloudy eyes.

    2. Exposure/Temperature – dry eyes are made worse from wind and low temperature exposure. Keep them shielded to reduce the drying out effect. I will definitely wear clear wraparound glasses on my next ultra.

    3. Eye glands – I am occasionally affected with Blepharitis ( which comes on every now and again as a result of seasonal allergies. Basically the eyelid oil glands get clogged and don’t allow eye oil to mix with eye moisture to form the film over the eyeball that helps protect it. Dr. recommended to double up on body oils such as flax seed and Omega 3 to ensure enough oil in the body. Then he suggested massaging the eyelids before a race to make sure they are not in a marginal state before the start.

    4. Artificial Tears – Dr. suggested that if the eyes begin to appear cloudy to treat with eyedrops immediately to stave off any further drying out.

    So for me that means a good eye massage and extra oil intake before my next cold ultra and good clear eyeglasses and eyedrops in my ultra kit.


    DavidF UPDATE June 2018:
    After finishing 4 more 100 milers (one each year – either Wasatch 100 or Bear 100) and a few cold-weather marathon-distance races each year, for me the resolution is to wear clear wrap-around glasses. It seems to provide just enough eye protection to keep my eyes from drying out prematurely and also keeps them warmer. When it’s colder I also use a buff to push warm moist air up into the bottom of the glasses. This combo works for me. While I carried eye drops for a few events in 2014 I found I didn’t need the drops. My eyes (especially the left one) do get a little hazy every now and then on cold training runs but never bad enough to dramatically impair my vision like it did at Bear 100 2013.

    My oldest son just started ophthalmology residency at WashU so this topic is truly near and dear to my heart. I’ll consider packing sodium chloride drops on training runs and report findings.

    Thanks again!

  39. Brian Silver

    For what it’s worth, at the end of the Mohican Trail 100 in 2010, a young woman, in her 20’s I think, reported blindness after she crossed the finish line. Having earlier given another runner sodium capsules for muscles cramps and agitation at mile 50 of the race, with successful results in a bout 30 minutes, I decided to do the same for her. After about 20 minutes, her blindness resolved. I wondered about a sodium disturbance in ultra runners as a cause of neurological disturbances in at least some of these events. (I work as a neurologist).

  40. Allan Couch

    Heidi Hehn, good thought but Lutein has been tested for the posterior portion of the eye (“retinal diseases”) but no benefit for the front part (cornea).

  41. Paula Lawton-Archer

    I am interested in the comments by Brian Silver posted above. I experienced exactly the same symptoms as in the article about 70 miles in to a 100 mile ultra in the UK. The weather conditions at the time were not extreme. It was raining at the time, and came on during the night section. I also thought it could be my contacts , so ditched them at the 77 mile CP. However, my vision remained cloudy. I was able to see a table that had food on it (I knew it would be food!) but I was unable to tell what anything was. I ran off bumping into hedges and ran straight into a metal farm gate. During the wooded section, I was falling over rocks and routes every couple of steps – at this point being dragged along by my pacer who ran with me until that 77 mile CP. I started to try and work out what it could be and began to take on more electrolyte tablets and also tried hard to increase my food intake (not easy!) anyway, whatever I did must have had a positive effect, as by mile 90 it had cleared and I finished the race with perfect vision again! Just thought it might be useful ti hear from someone who was able to clear it whilst still in the race. It has to be said though, that at that point I was forced to do a lot of walking, so maybe it wouldn’t have cleared if I was fuill on running??

  42. Matt H

    I had an incident with this yesterday just outside of Moab, UT.

    I was mountain biking the 100 mile White Rim Trail, solo and self supported in one day. No eye protection initially. Started in darkness. Sunny day, but freezing temperatures. Started in 20 degrees and warned to 40 maybe during the late morning.

    3 hours into ride I started having minor cloudiness. Figured it was just my contacts getting fogged or smudged. Put on sunglasses at 4 hours and mile 45 or so but vision was already clouding substantially.

    By 5 hours and 63 miles into the ride my vision was so clouded and white I could no longer operate my mountain bike safely. I was in the back country alone and luckily was able to find rescue from another group riding their bikes behind me with a support vehicle. They allowed me in their vehicle and drove me out to safety.

    My vision recovered fully within 4 hours or so of being in the heated truck. I am suspecting corneal edema. Unfortunately I did not receive a visual examination of my eyes during vision loss. It was painless. Vision was milky white and cloudy. I have no history of LASIK or eye surgery and I have no history of events like this or any UAVI.

    Thank you for posting all of this information.

  43. Peter Kirkham

    Matt H.,
    Welcome to the club matey….unfortunately for you!! It happened to me the first time I ran across the Grand Canyon solo and basically had to be led out by another runner who was climbing out to the South Rim. It has happened to me too numerous times over the past 20+years to mention now, mainly when I’m really pushing the pace (both MTBing and running/hiking) and/or in cool/cold conditions. I wear contacts and and the effects you describe are what I suffer from. No medical practitioner has been been able to explain our predicament!!! That’s why I’ll never try a 100 mile trail race as I know it will come on and I’ll have to either wait, 3-4 hrs, or DNF….pretty frustrating!!!

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