The medical terms for the rather trivializing name snow blindness are actinic keratosis and photokeratitis. It is damage to the cornea of the eye caused by strong UV radiation such as can typically occur when spending time in snow at high elevations or, for example, watching electrofusion with an unprotected eye. Depending on the severity of the burns to the cornea, snow blindness can be extremely painful and cause a foreign body sensation in the eye. In more severe cases, immediate ophthalmologic treatment is recommended.
What is snow blindness?
The two medical terms actinic keratosis and photokeratitis indicate damage to the cornea caused by radiation, or light exposure. The cornea seals the eyeball to the outside and performs important functions for vision such as refraction and unobstructed passage of incident light rays. The outermost layer of the cornea, which – similar to “normal” skin – is constantly renewed, is always wetted with tear fluid in order to be able to perform its functions. In case of too strong UV radiation, the outermost layers of the cornea can be literally “burned”, which then constitutes snow blindness. Since the cornea of the eyeball is crisscrossed by numerous nerve endings, damage to the cornea due to UV radiation can lead to severe pain and extreme sensitivity to light after a latency period of 3 to 12 hours.
Causes
Unprotected eyes can tolerate daylight and also sunlight (not directly into the eyes) in normal snow-free environments without damage. Increased UV in sunlight can cause repairable but also irreparable damage to the cornea. The cornea absorbs much of the UV-A and UV-B in sunlight, protecting the retina and especially the macula at the back wall of the eyeball, the small area of the retina that allows us to recognize colors and see sharply. When the UV-B component in the incident light becomes too strong, the uppermost layers of the cornea swell like edema and uncontrolled ablation of the dying cells occurs. This process is comparable to a mechanical injury of the cornea. Increased UV, to which the eye should not be exposed unprotected, occurs mainly in high mountains during skiing, at sea in southern latitudes, and at high altitudes (airplane cockpit).
Symptoms, complaints, and signs
If the eyes are exposed to sunlight for too long without protection, they can be damaged. Snow blindness is somewhat similar to sunburn of the skin. Instead of the skin on the back or shoulders, the cornea and conjunctiva burn here. The snow reflects the sunlight particularly strongly. Therefore, the symptoms occur especially after spending time in the snow. The symptoms appear a few hours after unprotected eye contact. It can take up to twelve hours before the affected person experiences great pain in the eyes and feels a foreign body sensation. The patient believes he has gotten sand in his eyes and feels the urge to rub it out of his eyes. The conjunctiva reddens and swells. The symptoms are roughly comparable to conjunctivitis. Likewise, the eyes often begin to water. A spasm of the eyelids is also typical of snow blindness. Since the eyes are particularly sensitive to light, the affected person frequently closes the eyelids. This happens compulsively. The condition, also known as photokeratitis, may also cause mild visual disturbances. In some cases, sunburn has also been observed on the skin at the same time. The symptoms are usually harmless and subside within two days at the latest. If this is not the case, the ophthalmologist should be consulted.
Diagnosis and course
Reddened and slightly burning eyes may provide the first indication of snow blindness. If the eyes have previously been exposed to increased UV radiation without protection, e.g., by skiing in high mountains or after spending hours at sea, this strengthens the suspicion of the presence of snow blindness. If the symptoms become more severe, an examination and diagnosis should be made by an ophthalmologist. The extent to which the cornea has been damaged can be diagnosed using a slit lamp and fluorescein staining. Severe cases of photokeratitis can lead to irreparable impairment of vision as a result of scarring in the cornea.If one or more of the symptoms described below occur, specialist care should be sought immediately:
Complications
Snow blindness or blinding may be accompanied by severe pain because the nerve endings of the UV-damaged outer cornea are exposed. At the same time, the eyelids tighten so that it is no longer possible to open the eyes. Depending on the severity of the blinding, vision may be lost for hours or even days. In order to immobilize the eyes and, if necessary, treat them with antibacterial agents and thus prevent possible complications, it is essential to consult a doctor – even if the symptoms seem to subside quickly. Complications can arise from additional inflammation of the cornea, among other things. Also desquamation of the retina is possible as a consequence of blinding, whereby the healing process is prolonged, the painful sensations are prolonged and the ability to see is only regained with a delay. Without medical treatment, there is a risk of super or secondary infections. This leads to an additional bacterial infection of the damaged tissue. This in turn can lead to permanent blindness in the worst case. Complications during the healing phase or additionally occurring pain should in any case be reported to the attending physician so that the treatment measures can be adjusted if necessary.
When should one go to the doctor?
In the case of snow blindness, a doctor should be consulted in any case. In the worst case, snow blindness can lead to complete blindness of the affected person and therefore significantly complicate the patient’s everyday life. To prevent further complications and discomfort, the affected person should contact a doctor at the first signs of snow blindness. A doctor should be consulted if there is reduced visual acuity and the conjunctiva reddens or even swells. A doctor should be consulted especially after spending time in snowy areas if these complaints occur and do not disappear again on their own. In general, visual disturbances indicate snow blindness and should be investigated if they have occurred without any particular reason. As a rule, a doctor should be consulted after two or three days at the latest if these complaints have not disappeared on their own. In this case, snow blindness is treated by an ophthalmologist. In emergencies, however, a hospital can also be visited. The life expectancy of the affected person is not limited by snow blindness.
Treatment and therapy
Mild forms of snow blindness heal by themselves after 2 – 3 days, because the uppermost corneal layers regenerate independently by natural resupply. Similar to the skin, newly formed cells are constantly supplied for the rejected cells. Immediate measures for more severe forms of snow blindness include staying in a darkened room, bed rest and cooling compresses on both eyes. In more severe forms of the disease, therapy is aimed at pain management, prevention of infections on the injured cornea and supportive measures to promote the natural regeneration of the cornea. For acute pain treatment, only a single application of locally effective eye drops is recommended, because repeated application of the drops increases the already existing damage to the epithelial layer of the cornea. If the pain persists, systemic pain treatment by taking common analgesics such as ibuprofen and others may provide relief. This may be accompanied by the use of anti-inflammatory and analgesic eye drops. Disinfecting antibiotic-containing eye ointments may be considered to prevent superinfection of the cornea.
Prevention
The best protection against snow blindness is provided by suitable sunglasses that almost completely filter out UV light up to 380 nm and also strongly filter out protection in the violet and blue range up to about 480 nm. Glasses that meet this requirement are labeled UV-400. For the remaining wavebands, lenses provide good protection if light transmission is 2%-8% in the blue range, 10%-40% in the red to green range, and less than 50% in the infrared range (above 780 nm).
Aftercare
Follow-up care by an ophthalmologist is necessary and even essential for snow blindness.Severe courses of the disease can lead to irreversible damage to the corneas and conjunctiva. Because of such dangers alone, medical aftercare is absolutely necessary to preserve the eyesight of the affected person. Professional aftercare is necessary for the relief of painful symptoms alone. The direct influence of particularly intensive UV radiation triggers the symptoms. In mild courses, no permanent damage remains. Nevertheless, a follow-up is advisable to check the completed healing process again. The patient can take care of himself in the future by avoiding bright light sources. Sunglasses have a supporting effect here. A further disease flare-up is prevented. Instead of aftercare, preventive care makes sense in this case. If there is no noticeable improvement after two to three days, the ophthalmologist will arrange for further examinations. The aim is to determine which eye disease actually underlies the complaints. The progress of healing will be monitored at follow-up appointments. Surgery may be required to completely eliminate the disease. Regular check-ups after the inpatient stay are common in any case. The physician will check to see if the eyes have healed as expected.
What you can do yourself
The best self-help measure for snow blindness is to take precautions. The risk of blinding is particularly high during winter sports in high mountains. Therefore, sunglasses suitable for high mountains or appropriate ski goggles should always be worn when the weather is fine and the sun is intense. Water reflects UV rays strongly, but not only when frozen. The risk of snow blindness therefore also exists during water sports or boat and ship trips. Even crossing smaller bodies of water on a ferry can be risky in strong sunlight. Good sunglasses should therefore also be worn on these occasions. In solariums, protective glasses handed out by the staff must be used without fail, as the risk of damage to the eyes from UV light is particularly high here. If the eyes are nevertheless blistered, shade must be provided immediately and a doctor, or better still an ophthalmologist, must be consulted. If those affected do not have protective goggles with them, they should borrow one for the way to the doctor in order to relieve the injured eyes as much as possible. The eyes often react to the corneal erosion caused by the UV radiation with strong itching, in addition often a foreign body feeling sets in. Nevertheless, do not scratch or touch the eye under any circumstances, otherwise there is a risk that the damaged cornea will become inflamed.