Snow blindness is a burn injury of the eye associated with damage to the conjunctiva and cornea by ultraviolet, infrared or powerful visible radiation. Snow blindness is manifested by signs of keratoconjunctivitis: photophobia, blepharospasm, lacrimation, swelling of the conjunctiva of the eyelids, erosions and ulcers of the cornea, temporary loss of vision. The diagnosis of photophthalmia is based on the data of anamnesis and visual examination, biomicroscopy, instillation fluorescein test. The treatment of snow blindness requires the creation of complete visual rest, the application of a dense blindfold, instillation of disinfectant drops.
H16.1 Other superficial keratitis without conjunctivitis
Snow blindness (photophthalmia, electrophthalmia) includes inflammatory eye diseases of non-infectious etiology caused by exposure to radiant energy. In ophthalmology, it is customary to include ophthalmia caused by infrared, ionizing radiation, UV rays (snow blindness), radiation from electrical sources (electrophthalmia) as radiation damage to the eyes. In this case, there is usually a superficial burn of the eye (eyelids, conjunctiva, cornea, sclera), the phenomena of blepharitis, conjunctivitis, keratitis develop.
Causes of snow blindness
Snow blindness (electrophthalmia) develops in people exposed to ultraviolet radiation, especially in the range UV-B (290-320 nm), UV-C (100-290 nm).
UV-B – ultraviolet waves of the medium wave range, acting on the skin, cause the development of solar dermatitis, and, getting into the eyes, are absorbed by the cornea and lens. Short-wave ultraviolet (UV-C) is absorbed by the ozone layer of the Earth, but the radiation of this spectrum is used in artificial sources: in medicine and cosmetology (quartz lamps, lasers), electric welding, etc. Short-wave UV-C rays are completely absorbed by the conjunctival and corneal epithelium, leading to the development of photophthalmia.
Under the influence of absorbed rays, DNA and epithelial cell membranes are damaged by free radicals and reactive oxygen species, which manifests itself in the development of necrobiosis, subepithelial vesicles, histamine accumulation, tissue edema and vasodilation.
Snow blindness develops in people exposed to ultraviolet radiation reflected from the snow surface – skiers, climbers, polar explorers, winter fishing enthusiasts, etc. Electrophthalmia associated with artificial radiation can occur when irradiated with bactericidal lamps in the staff of physiotherapy, treatment rooms, operating rooms; visitors to tanning salons; patients with skin diseases (psoriasis, atopic dermatitis, vitiligo) receiving PUVA therapy; electric welders and people watching welding without eye protection with light filters.
Ultraviolet has a cumulative effect, so the symptoms of snow blindness and electrophthalmia develop 4-6 hours after exposure.
Other radiation damage to the eyes
Infrared radiation with a wavelength of 500,000-760 nm causes thermal damage to the eyelids, conjunctiva, and anterior segment of the eyes. The internal environments of the eye (lens and retina) are most sensitive to rays in the range of 900-1000 nm. With prolonged exposure to the eyes of sources of infrared radiation (metallurgists, blacksmiths, glass smelters, rollers), chronic blepharitis, conjunctivitis and the so-called “thermal” cataract can develop. When the retina is affected, central scotomas and a decrease in visual acuity occur.
The visible part of the spectrum, which acts continuously for a long time, can also pose a danger to the organ of vision. Such electromagnetic radiation affects the photoreceptors of the macular zone of the retina and poses a threat to macular dystrophy (chorioretinal dystrophy).
Ionizing radiation emitted by X-ray machines, cyclic accelerators, nuclear reactors, radioactive isotopes, etc., is completely absorbed by the eyeball. High doses of radiation can lead to atrophy of the eyelid skin, loss of eyelashes, scarring of the conjunctiva, erosions and ulcers of the cornea, the development of cataracts.
The first complaints of discomfort and “sand” in both eyes appear a few hours after ultraviolet irradiation. The clinic of snow blindness and electrophthalmia is characterized by a pronounced corneal syndrome, including acute pain in the eyes, blepharospasm, photophobia and lacrimation. Objectively, the presence of hyperemia and edema of the eyelids, conjunctival or mixed injection, conjunctival edema is detected.
The cornea can retain its luster and transparency, however, with prolonged exposure or increased individual sensitivity to ultraviolet light, epithelial edema, single vesicles and spot erosion of the cornea often develops.
The progression of the symptoms of snow blindness and electrophthalmia leads to intolerance to even weak light, and in a few hours complete loss of vision may occur.
The diagnosis of snow blindness and electrophthalmia is established by an optometrist on the basis of anamnesis (the fact of exposure to UVI); typical clinical symptoms developing a few hours after exposure; data from an objective ophthalmological examination.
Vision testing (visometry) in patients with snow blindness is usually difficult due to convulsive compression of the eyelids. However, in all cases there is a temporary decrease or complete loss of vision.
An objective examination of the eyes (biomicroscopy, ophthalmoscopy) is possible only after the installation of drops of local anesthetic, allowing to eliminate the corneal syndrome. With snow blindness and electrophthalmia, signs of photodermatitis of the eyelids, vascular injection, swelling and hyperemia of the conjunctiva are revealed, with damage to the retina – changes in the fundus.
Corneal changes in the form of point erosions or ulcers are determined during the fluorescein instillation test.
Treatment of snow blindness
Emergency care for electrophthalmia and snow blindness requires complete visual rest: it is necessary to apply a light-tight dark bandage to the eyes, the victim’s stay in a darkened room.
Drug therapy of snow blindness and electrophthalmia is aimed at relieving the phenomena of keratoconjunctivitis, preventing infection and stimulating epithelialization of corneal defects.
In case of snow blindness, instillations into the conjunctival sac of solutions of anesthetics (dicaine, trimecaine) and disinfectant drops (sulfacetamide), metabolites, artificial tears are prescribed. Ointment applications of erythromycin or tetracycline are made. It is allowed to use local cold lotions on the eyelids in order to reduce the severity of edema.
Antihistamines (chloropyramine) and NSAIDs (diclofenac) are prescribed from systemic drugs for snow blindness.
Prognosis and prevention
The phenomena of snow blindness and electrophthalmia usually subside without a trace after 2-3 days, while vision is fully restored. In some cases, hypersensitivity to bright light may persist for a long time.
Prevention of snow blindness and electrophthalmia consists in the use of protective glasses with light filters, compliance with safety regulations when working with artificial emitters.