The harmful effects of light
Some beneficial effects of light such as vision of shapes, vision of colors… are well known to everyone and obvious. Others like the biological clock, the action on the psyche are less so and benefit from advances in medical research.
- The harmful effects of light:
The harmful effects of light have been known since Antiquity and are still the focus of many studies:
- Ocular toxicity can be related to excess photons per dose acutely or chronically.
- Even invisible IR and UV rays act insidiously on the eye.
- IRs are responsible for the sensation of heat, dryness of the cornea and visual fatigue.
- The Ultra Violets:
This is a very complex area of the light spectrum which is the subject of many studies.
- UVA rays: they represent 95% of UV radiation and are responsible for skin pigmentation and are also the most dangerous for the eyes. They reach the lens in adults, and in children penetrate to the retina. The lens lets through 90% of UVA in children under 1 year old and 60% before 13 years old.
- UVB: they are less important since they represent only 4% of UV but they are the most dangerous for the skin (erythema, tumour, etc.). They are 80% filtered by the lens in adults but only 50% before 1 year and 25% before 10 years.
- UVC: these are the most dangerous but they are fortunately stopped by the ozone layer.
- Increased risks for our eyes:
The decrease in the thickness of the ozone layer, modern life, the lengthening of life, the resurgence of artificial light sources, the appearance of new LED light sources (excess of bad blue light), the use to photo-sensitizing medications are all risk factors.
It is also necessary to take into account the altitude and the reflective surfaces that surround us (water, snow).
- The most exposed populations are:
children because their pupils are wide, their lens transparent and the time spent outdoors without sun protection is important
mountain or sea professionals
Eyelids: sunburn, eyelid skin cancer, melanoma, blepharitis
Conjunctiva: pterygium, chronic conjunctivitis
Cornea: photo-keratitis, snow blindness
Lens: exposure to UVA and UVB increases the risk of cataracts
Retina: AMD: blue light is harmful, retinitis pigmentosa
- Means of protection:
Natural protection: indeed the eye is located in the eye socket and is also protected by the eyelids and eyelashes. The squinting reflex during glare and the reflection of certain rays by the tear film.
Or with contact lenses with UV filter: few have them. And be careful, they only protect the cornea and the internal membranes. They do not cover the eyelids and the entire conjunctiva.
- Elements favoring the harmful effects of UV rays:
Many drugs are photosensitizers; this is the case with certain antibiotics, antifungals, antidepressants and anti-inflammatories. This is also the case for certain dermatological diseases. It is strongly recommended to reduce exposure to UV radiation as much as possible
As Doctor Bury, an ophthalmologist in Paris, explained to us during the Silmo Academy, IR and UV rays and some of the blue light have proven harmful effects on the eye . It is therefore essential to protect yourself, especially children and adolescents.