What are the effects of ultraviolet radiation on the eyes?
The main natural source of ultraviolet radiation (UVR) is the sunlightso all individuals are exposed to a certain dose of UVR on a daily basis. In addition, there are many artificial sources of UVR, such as tanning lamps, table-top halogen lamps and lights used for professional photo sets.
The skin damage caused by UVR is well known (melanoma, carcinoma, keratosis, etc.), but less well known is the damage that this radiation may cause to the eyesdespite the fact that the eyebrows, eyelashes and pupillary constriction act as protection for the extreme light.
UV radiation is invisible to the human eye, has wavelengths between 100 and 400 nm (nanometres) and is divided into three bands: ultraviolet A-UVA315-400 nm; ultraviolet B-UVB280-315 nm and ultraviolet C-UVC, 100-280 nm. Shorter wavelengths have a higher energy and an increased potential for ocular damage: the biological damage potential at 300 nm is 600 times greater than at 325 nm. The ozone layer efficiently absorbs the shorter wavelengths; all UVC radiation and around 95% of UVB radiation are absorbed, so the UVR that reaches the Earth's surface are 95% of UVA and approximately 5% of UVB.
An analysis published in Journal of Postgraduate Medicine analysed 43 studies concerning the effects of ultraviolet radiation on the eyes (particularly on ocular tissues and corneal complications), also considering the travel parameter.
The results of the analysis showed that UV radiation at 300 nm causes apoptosis after 5 hours of exposure, i.e. a condition in which cell death occursin all three layers of the cornea. The intensity of the effect of UV radiation on the eye is related to several factorsThese include solar elevation, time of day, season, hemisphere, clouds and haze, atmospheric scattering, atmospheric ozone, latitude, altitude, longitudinal changes, climate, ground reflection and geographical directions. Of these, the most relevant in influencing UV radiation reaching the earth's surface is solar elevation. Among the ocular effects the photokeratitis represents the more acute corneal response to UVB and UVC radiation exposure, and it is believed that travelling increases the risk even more.
La photokeratitisalso known as snow blindness or arc blindness, presents with symptoms that include tearing, reddening of the eye and pain, photophobia, swollen eyelids, headaches, seeing halos around light sources, blurred vision and temporary loss of vision. This inflammatory condition is transient, generally occurring up to 6 hours after UV exposure and resolving within 48 hours, usually without long-term consequences.
Various photo-protection systems can reduce the potential risk of UV radiation causing eye damage, among them: avoiding direct exposure to sunlight, wearing UVR glasses (sunglasses or contact lenses), wearing hats and using an umbrella. The main method of prevention is avoid sunlighteven in cloudy weather.
As for the sunglassesThese should ideally block all UV rays, blue light and not affect contrast and colour discrimination. In terms of photo-protection, one must also consider the size, style and position of sunglasses, the eyes can also be damaged by the UV rays from diffuse and reflected light coming from the peripheral eye area. For this reason, small sunglasses increase the probability of UVR reaching the eyes from the sides of the sunglasses, and this is especially important in special conditions, i.e. when UV rays reflect from the ground, snow, water and sand indirectly. Furthermore, moving the sunglasses about 6 mm away from the forehead results in a 20% greater increase in the amount of UV rays reaching the eyes. Another method used to protect the eyes against UV radiation is the use of contact lenses that also block out peripheral light, that temple sunglasses cannot shield.
The role of UV radiation in eye diseases is an important public health problem that is often underestimated by the global population. For this reason, the most important action to prevent the effects of UV radiation on the eyes should include Actions aimed at informing and educating the population about the risks of UV exposure and methods of prevention.
Source
Dr. Carmelo Chines
Direttore responsabile