|Effects of Blue Light on Ocular Health
UV light and blue light
It has been well established that ultraviolet (UV) light is hazardous to the human eye causing cataract and retinal degeneration. UV light is defined as that part of the invisible spectrum of light ranges from 380nm to 200nm. More recently, scientific evidence is emerging indicating that near UV or “blue light” may also be hazardous and have adverse effects to ocular structures. Blue light is that light with wavelengths in the 500nm to 381nm range. Of special concern is the blue light given off by “black light” tubes and bulbs which are commonly found in night clubs and bars. This blue light causes objects to fluoresce under black light and is deemed desirable by party goers and trend setters.
Animal studies since 1980 has shown that prolonged exposure of high intensity blue light resulted in inflammation and damage to the retinal pigment epithelium (RPE). The RPE is a very delicate layer of cells which is essential in the maintenance and function of the retinal photoreceptors (also known as rods and cones). Melanin, a common pigment component found in high concentration in the RPE strongly absorbs blue light resulting in oxidative damage to the RPE cells. The human eye has natural protection against exposure to blue light. Both the human lens and lutein, a yellow pigment found in high concentration in the macula (the centre of the retina) filter blue light thereby offering some but inadequate protection to the photoreceptors. This repeated phototoxicity and injury eventually leads to permanent damage to the retina causing age related macular degeneration (AMD). AMD is the commonest cause of irreversible blindness in old age which is untreatable in most cases. Recognizing the hazard of blue light, ophthalmologists (eye specialists) have been using blue light filter in their lens and equipments while examining patients. Additionally, intraocular lens companies incorporate blue light filter in the intraocular lens in order to reduce the exposure of the retina to blue light following cataract surgery.
The human lens strongly absorbs UV and blue light and thus acts as a protective shield for the retina. Prolonged exposure of the lens to UV and blue light can lead to gradual yellowing of the lens and eventually to cataract formation. Thus the lens becomes a natural but imperfect absorber of UV and blue light and helps protect the retina from these harmful light. Most authorities now believe that UV and blue light absorbed by the lens is a major contributing factor to cataract formation. So in shielding the retina from the harmful effects of UV and blue light, the lens becomes cataractous.
Glasses/ Sun glasses
Both the retina and lens should be protected throughout life from both UV and blue light radiation. This would delay the onset of cataract and age related macular degeneration. This is particularly relevant in persons who are myopic (shorted sighted) as the retina of persons who are myopic are thinner and are more susceptible to damage.
Recent studies have shown that neither the human cornea nor the natural lens provides sufficient protection from blue light in our modern environment. Additionally, young people under the age of 20 have little or no yellowing of the natural lens. Any UV or blue light which enters the eye are unfiltered and strikes the retina at full strength. The amount of UV and blue light entering our eyes can be effectively reduced by wearing sunglasses. Even clear plastic spectacles e.g. polycarbonate spectacles have the ability to filter out UV light. However they will not filter blue light. Yellow tint filter allows the best contrast for most people while offering UV and blue light protection.
Avoidance of UV and blue light
UV and blue light exposure can be limited by taking a few simple precautions in addition to wearing the appropriate glasses/ sun glasses. Black light usage in parties and clubs should be reduced. If possible, substitute cool white fluorescent tubes, full-spectrum lights, daylight tubes or bulbs, or mercury lights with warm white tubes or incandescent lamps.
Food substances rich in vitamin A, lutein, beta carotene, xeaxanthin and anti-oxidants have a protective effect against AMD. Green vegetables and brightly coloured fruits and vegetables are rich sources such nutrients and should be consumed regularly.