Snow Blindness: “Photokeratitis”

Photokeratitis is a condition like a “sunburn of the eye.”
It is inflammation of the front of the eye.
Cornea: the thin, transparent surface layer that forms the window at the front of the eye
Conjunctiva: the transparent tissue covering the white of the eye and the inside of the eyelids

Several hours after ultraviolet light hits the eye directly,
damage mainly occurs in the cornea (the black of the eye).¹。

TOC

Snow Blindness: “Photokeratitis”

Causes of Snow Blindness: “Photokeratitis”

Photokeratitis is caused by damage to the eye from ultraviolet (UV) light.
The main natural source of UV is sunlight.²。

Snow blindness (photokeratitis) is caused by
sunlight reflected off sand, water, ice, and snow.

Eye damage from UV is especially common in the Arctic and Antarctic regions and at high altitudes,
because the air is thin and blocks UV less well.³。

Snow blindness can also refer to
freezing of the corneal surface,
or severe drying of the corneal surface due to extremely dry air.

Skiing, snowmobiling, and mountain climbing can cause this condition.

Artificial sources of UV include

tanning lamps,
tanning beds (tanning machines),
laboratory UV lights,
germicidal UV lights,⁴
sun lamps,
broken metal halide lamps (such as those in gymnasiums),⁵
arc welding,
and others.

Wearing appropriate eye protection can prevent eye damage from UV light.

Caution is needed when staring at the sun itself (for example, when watching a solar eclipse).

During an eclipse, a burn can occur in the “retina” at the back of the eye.
This is permanent damage to the retina and causes severe visual impairment.
It is more serious than temporary damage to the cornea.

Symptoms of Snow Blindness: “Photokeratitis”

As with a “sunburn,” people often notice only after the eyes have been damaged.
The main symptoms are as follows.

Eye pain
Redness
Blurred vision
Tearing
A gritty feeling in the eye
Swollen eyes
Sensitivity to bright light
Headache
Seeing halos
Small pupils
Eyelid twitching
Temporary decrease in vision
Temporary change in the color of vision

The longer the exposure to UV, the more severe the symptoms.

Diagnosis of Snow Blindness: “Photokeratitis”

We ask about recent activities and examine the eyes,
and diagnose photokeratitis by using eye drops containing fluorescein dye to check for UV damage.

It is distinguished from the following (differential diagnosis)

Viral conjunctivitis (pink eye)

It can occur in both eyes and may show similar findings.
In viral conjunctivitis (pink eye), one eye is generally affected first, with clear redness and swelling of the conjunctiva.
In photokeratitis, both eyes are affected at the same time, and conjunctival inflammation is relatively mild.

Prolonged contact lens wear

Eye damage caused by contact lenses is distinguished from photokeratitis.

Dry eye

Reduced tear volume
Instability of the tear film (BUT, breakup time: judged in the exam room with fluorescein staining)
and no history of UV exposure
lead us to considerdry eye.

Toxicity of eye drops

Glaucoma eye drops and antibiotic eye drops:
we consider hypersensitivity or toxicity to eye drops such as brimonidine, neomycin, and tobramycin, and to topical medicines containing preservatives.

Exposure to chemicals

Cleaning sprays, oven cleaners, and other chemicals can cause symptoms and findings similar to photokeratitis.

Foreign body under the upper eyelid (something has gotten into the eye)

It is usually on one side only.
In the case of a foreign body under the upper eyelid (something has gotten into the eye),
examining the cornea under the microscope usually shows linear abrasions running vertically.

How to Treat Snow Blindness: “Photokeratitis”

Snow blindness (photokeratitis) usually heals on its own.
The corneal epithelium recovers quickly and heals in 24 to 72 hours.
Treatment therefore mainly focuses on easing pain while the eye recovers.

If you wear contact lenses, please remove them right away.

Artificial tears, eye ointment, and oral pain relievers are used.

Eye patching is not recommended⁶。

To relieve symptoms,
please avoid rubbing your eyes during the healing period.
(When it hurts, apply eye ointment and keep the eyes closed.)
Placing a cool cloth over the closed eyes also seems to be helpful.

Prevention of Snow Blindness: “Photokeratitis”

Photokeratitis can be prevented by wearing eye protection that blocks UV light.⁷。

This includes the following.

Sunglasses that block or absorb 99% or more of UV light
Snow goggles that block UV light
Welding helmets

References

Cullen, A.P., 2002. Photokeratitis and Other Phototoxic Effects on the Cornea and Conjunctiva. Int J Toxicol 21, 455–464. https://doi.org/10.1080/10915810290169882
Zinflou, C., Rochette, P.J., 2017. Ultraviolet A-induced oxidation in cornea: Characterization of the early oxidation-related events. Free Radical Biology and Medicine 108, 118–128. https://doi.org/10.1016/j.freeradbiomed.2017.03.022
Dolin, P.J., Johnson, G.J., 1994. Solar ultraviolet radiation and ocular disease: a review of the epidemiological and experimental evidence. Ophthalmic Epidemiology 1, 155–164. https://doi.org/10.3109/09286589409047224
Sengillo, J.D., Kunkler, A.L., Medert, C., Fowler, B., Shoji, M., Pirakitikulr, N., Patel, N., Yannuzzi, N.A., Verkade, A.J., Miller, D., Sliney, D.H., Parel, J.-M., Amescua, G., 2021. UV-Photokeratitis Associated with Germicidal Lamps Purchased during the COVID-19 Pandemic. Ocular Immunology and Inflammation 29, 76–80. https://doi.org/10.1080/09273948.2020.1834587
Finn, L.E., Gutowski, J., Alles, S., Mirowitz, N., Johnson, C., Osterhoudt, K.C., Patel, A., 2016. Photokeratitis Linked to Metal Halide Bulbs in Two Gymnasiums — Philadelphia, Pennsylvania, 2011 and 2013. Morbidity and Mortality Weekly Report 65, 282–285.
Turner, A., Rabiu, M., 2006. Patching for corneal abrasion. Cochrane Database of Systematic Reviews. https://doi.org/10.1002/14651858.CD004764.pub2
Mortazavi, S.M.J., Hashemi, M., Haghani, M., Namavar, S., Masoumi, S., Eghlidospour, M., Daneshmandi, H., 2014. Screening study of the efficiency of common sunglasses in blocking ultraviolet radiation and visible light by a novel simple method. Physica Medica: European Journal of Medical Physics 30, e48–e49. https://doi.org/10.1016/j.ejmp.2014.07.146