Some beneficial effects of light, such as shape vision, color vision, etc., are well known and obvious to everyone. Others, such as the biological clock and its effect on the psyche, are less known 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 subject of many studies:
- Ocular toxicity can be linked to an excess of photons, either from an acute dose or chronically.
- Infrared and ultraviolet rays, even invisible ones, act insidiously on the eye.
- IR rays are responsible for the sensation of heat, dryness of the cornea, and visual fatigue.
Ultraviolet rays:
This is a very complex area of the light spectrum that is the subject of many studies.
- UVA: 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 penetrate to the retina in children. The lens lets 90% of UVA pass through in children under 1 year old and 60% before 13 years old.
- UVB: They are less significant, as they represent only 4% of UV rays, but they are the most dangerous for the skin (erythema, tumors, etc.). They are 80% filtered by the lens in adults but only 50% before 1 year old and 25% before 10 years old.
- UVC: These are the most dangerous, but fortunately, they are stopped by the ozone layer.
Increased risks for our eyes:
The thinning of the ozone layer, modern life, increased life expectancy, the resurgence of artificial light sources, the appearance of new LED light sources (excessive harmful blue light), and the use of photosensitizing medications are all risk factors. Altitude and surrounding reflective surfaces (water, snow) must also be considered.
The most exposed populations are:
- children, because their pupils are wide, their lenses are transparent, and they spend significant time outdoors without sun protection.
- mountain or sea professionals
Pathologies:
- Eyelids: sunburn, eyelid skin cancer, melanoma, blepharitis
- Conjunctiva: pterygium, chronic conjunctivitis
- Cornea: photokeratitis, snow blindness
- Lens: exposure to UVA and UVB increases the risk of cataracts
- Retina: AMD (blue light is harmful), retinitis pigmentosa
Protection methods:
Natural protection: the eye is located in the eye socket and is also protected by the eyelids and eyelashes, the reflex of squinting when dazzled, and the reflection of certain rays by the tear film.
Optical protection: this is generally done with sunglasses or blue light blocking glasses and varies depending on the material and tint of the chosen lenses.
Or with UV filter contact lenses: few have them. And beware, they only protect the cornea and internal membranes. They do not cover the eyelids and the entire conjunctiva.
Factors promoting the harmful effects of UV:
Many medications are photosensitizing; this is the case with certain antibiotics, antifungals, antidepressants, and anti-inflammatories. This is also the case with certain dermatological diseases. It is strongly advised to minimize exposure to UV radiation.
As ophthalmologists explain, IR, UV, and part of blue light have proven harmful effects on the eye. It is therefore essential to protect oneself, especially children and teenagers.
