Ultramarathon-induced Corneal Edema

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Ultramarathon-induced Corneal Edema is a transient condition that develops during prolonged physical exertion.

Disease Entity

Possible ICD-10-CM code:

H18.20 Unspecified corneal edema

UMICE in a participant of a Crosscountry ski ultramarathon

Disease

Ultramarathon-induced Corneal Edema (UMICE) is corneal edema that develops during prolonged physical exertion, typically ultramarathons, and it usually resolves within hours after cessation of exercise (1). It is mostly described in foot races of ultramarathon distance (more than 42,2 km) but it may occur in shorter endurance distances and in other endurance sports such as bicycling (2) and cross-country ski ultramarathons (unpublished cases).


SYMPTOMS AND SIGNS:

- Progressively painless blurred vision due to corneal edema in one or two eyes during prolonged physical exertion, typically races at ultramarathon distances. It reverses usually within hours after cessation of exertion.

- The vision loss has a blurry character but it may be profound.

- No photophobia or pain.

- The eye bulb is usually white or may have a slighter bulbar injection.

- Corneal edema.


RISK FACTORS:

It is not investigated whether corneal dystrophies or a low corneal endothelial cell count is a risk factor.

Corneal refractive surgery such as LASIK is a suspected risk factor (3).

External ambient factors causing stress to the cornea, such as wind direction, are suspected risk factors (1).


DIFFERENTIAL DIAGNOSES

A transient condition:

By the time a participant of an endurance race has reached an ophthalmologist or a physician the condition may have reversed substantially, the vision may be back to normal and there might be none or only discrete signs left of earlier corneal edema, such as slight "descemet's folds".

However, the very typical set of signs, symptoms, settings and course of UMICE (see above) is helpful for the clinican.

Differential diagnoses that give transient vision loss:

- Neuro-ophthalmological transient visual losses will unlike UMICE typically be shorter in time, come and go in a quick manner and also give darkening of vision rather than blurring of vision. It will not cause corneal edema.

- Tear film deficiency will usually not lead to a cloudy cornea and the visual blurring will usually be less profound than in UMICE.

- Uhthoff's phenomena in optic neuritis (ON) gives visual disturbances during exercises but the cornea will not be hazy. It is likely to be a history of symptoms of ON from before and after the race, a demyelinating disease may be known and clinical signs of ON can be seen during the examination after the race. It will not cause corneal edema.

- Pigment dispersion syndrome (see below).

- Uveitis-Glaucoma-Hyphema Syndrome (see below)


Differential diagnoses that can give rise to a rapidly hazy cornea include:

-Acute corneal hydrops in keratoconus. Unlike UMICE the acute corneal hydrops causes pain, photophobia and takes weeks to resolve.

-A rapid and significant rise of intraocular pressure. Unlike UMICE this would typically cause distinct pain and red-eye. Pigment dispersion syndrome (PDS) could potentially create a similar clinical picture to UMICE as it can lead to the release of iris pigment during exercise leading to raised intraocular pressure and blurred vision. Signs of PDS are Krukenberg spindle, spoke like iris atrophies, excessive pigmentation of the trabecular meshwork. Similar symptoms to PDS could happen in Uveitis-Glaucoma-Hyphema Syndrome where chafing from intraocular lens (IOL) implants leads to pigment dispersion or haemorrhaghes.

-Contact lens irritation can be differentiated from UMICE as it comes with a more superficial and epithelial hypoxic edema and as it commonly gives rise to a burning sensation or pain.

-“Eye dryness” is typically associated with foreign body sensation or pain and possibly eye redness. The cornea is usually not cloudy but it is a common cause of disturbed vision.

-Spontaneous or nonspontaneous corneal epithelial erosion is unlike UMICE associated with pain and photophobia.

-“Frozen cornea” or “wind blindness” is a painful condition that occurs in cold climates and has been described in for instance skiers and sled dog drivers (4).

Etiology

The current theory is that UMICE is caused by lactate-build up whitin cornea leading to corneal edema by means of osmosis and affection on the corneal endothelial pump. Lactate is a known metabolite in the corneal metabolism and it is well known that corneal accumulation of lactate can lead to corneal edema. A combination of external corneal stress, such as from wind or sweat, leading to raised internal corneal lactate production together with a systemic progressive rise of lactate in the blood and aqueous during prolonged physical exertion is thought to lead to the corneal lactate build up with subsequent edema. (5).

General treatment

Prophylactic measures that seem to help are lubricant drops and protective eyewear (3).

As UMICE already has developed cessation of exercise is the only known effective treatment.

Complications

Blurred vision has lead to physical injuries during races (1).

Long term effects on the cornea are not known and have not been studied.

Prognosis

Long term effects on the cornea are not known and have not been studied.

Patients who have had UMICE are advised to use protective eye wear and possibly lubricant drops

if they are to engage in similar races again as recurrences have been observed (3).

References

  1. Lindström, B. E., & Høeg, T. B. (2021). Ultramarathon-induced Corneal Edema—A Case Report. Current Sports Medicine Reports, 20(1), 13-15.
  2. Khodaee M, Torres DR. Corneal opacity in a participant of a 161-km mountain bike race at high altitude. Wilderness Environ. Med. 2016; 27:274–6.
  3. Høeg TB, Corrigan GK, Hoffman MD. An investigation of ultramarathon-associated visual impairment. Wilderness Environ. Med. 2015; 26:200–4.
  4. Cope TA, Kropelnicki A. Eye injuries in the extreme environment ultra-marathon runner. BMJ Case Rep. 2015; 2015:bcr2015210432.
  5. Moshirfar M, Ding Y, Ronquillo Y, et al. Ultramarathon-induced bilateral corneal edema: a case report and a review of the literature. Ophthalmol Therapy. 2018; 7:197–202.