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.

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.

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

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.”

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).

A graphic of refractive surgery. Image: lasersite.com

  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 Men’s Sg-1 Matte Adjustable Strap Sunglasses. Image: Amazon.com

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

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

Treatment

  • 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.

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

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 tracybethhoeg@gmail.com if you are interested in participating.

References

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.

View Comments (82)

  • What an incredibly well-written and interesting article!

    A+,

    JV

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  • 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.

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    • Good catch, Charlie, and corrected. I think we might have, in our minds, superimposed his DNF at The Bear with his second-place RRR 100 Mile finish. Sorry about that, Mark!

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  • 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.

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  • Very interesting. Regarding protective eyewear, what are we protecting against? Light/UV, debris, wind, temps?

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    • 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.

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  • If wearing contacts, would contact solution do the trick? Or would the 5% hypertonic saline drops need to be used?

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    • Ryne: contact lens solution won't work the same. You can use the sodium chloride (muro 125) drops over your contact lenses.

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    • Ryne, yeah, contact solution would not be expected to have the same effect as hypertonic saline. I agree with Sara.

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      • Thanks, Tracy and Sara!

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  • 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!

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    • 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.

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  • 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...

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  • 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.

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  • 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.

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  • 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.

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  • 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.

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  • 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.

    aft

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    • Jerry, glad to hear it! Can I ask what kind of drops worked for you?

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  • 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.

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  • Great article! Question: Did you consider analyzing humidity as a variable?

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    • 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?

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      • 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!

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  • 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.

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  • Please can you provide your email address to send information to the address in the article tracybethoeg@gmail.com does not work.

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    • It is tracybethhoeg@gmail.com. Thanks for noticing the typo, Stewart!

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  • 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.

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  • 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.

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    • 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.

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      • 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!

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  • 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.

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  • 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.
    -Maggatron

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