Interestingly, a research team which exposed animal eyes to radiation to the point of damage found that while UV lights harm eye tissue through photochemical and photomechanical means, the damage caused by IR wavelengths was probably thermal in nature. Several voices, including the study mentioned above, claim that there is some risk of thermal damage to your eyes in the sauna.
And there certainly is some risk: many of the benefits from IR saunas, after all, come from heat stress. Each body part responds to that stress differently. However, the risk of ocular damage from sauna heat is very low. The temperatures achieved during an infrared sauna session are not known to be toxic to any component of the human eye, even with regular usage.
Recommendations and legislations are already available concerning the protection requirements of sunglasses and safety eyewear [], but with the increasing life expectancy, the diffusion of spare time activities in intense exposure environments beach and mountain activities, sailing, etc.
The engineering of an IR filter for ophthalmic lenses is a relatively novel question, which can be partly faced following the examples of other optical industries: the most experienced among them is the safety eyewear sector producing the so called Personal Protective Equipment — PPE , where the protection strategy consists usually in incorporating IR absorbing dyes to the lenses, which can be on metallic or organic base: the nature and concentration of the tints depend on the use that the lenses are thought for, usually in combination with analogous UV absorbing pigments in PPE.
This approach brings to an unavoidable consequence: all the available IR-A absorbing dyes are not transparent to visible light, so all the functional IR-A filters will appear dark at some extent.
Another example is the precision optics manufactory: here, bandpass elements centered in the visible region are needed, with a high transparency inside the nominal band, so they are built under a different approach.
While the short wavelength region could be filtered again by absorbing dyes, the most common strategy for having a definite passing band, and in particular to eliminate the IR radiation, is to reflect out the unwanted wavelengths by an interference multilayer coating, opportunely tuned in thickness, number and composition of the layers, in order to obtain the sharpest possible frontier between the allowed and the blocked radiation.
In ophthalmic optics, the assembly of an effective IR filter is set on both the approaches previously mentioned: the issue is on the table since a relatively short time, but in the case of sunglasses, for instance, some degree of filtering was made available in the last decade by the inclusion of absorbing dyes, as for safety eyewear.
However, for an effective concentration, the colorants must be included in the casted polymer of the semifinished lens and not embedded on the finished product , and this almost excludes the applicability to prescription lenses.
An alternative can be inspired by the technology of heat mirrors [27], utilized in energy saving construction or solar energy production: here a thin layer of a metal, usually silver, is used for its low absorbance in the visible range, and high reflectance in the near IR at the same time [28].
However, the required Ag thickness and the need for protection from oxidation usually by sandwiching the silver between nanolayers acting as barriers , contribute to reduce the total transmittance of the stack.
The efficiency of the filter increases with the number of the layers, and consequently with the total thickness of the stack [29]. However, a thick and very structured multilayer involves several mechanical and aesthetical issues, like the scratch and thermal resistance of the coating, or the filter efficiency and aspect at different angles, that should be avoided.
Nowadays, a functional filter for the near IR waveband is already available from several manufacturers for the full range of prescription lenses. Indeed, of course the radiation intensities that we are subjected to in our everyday life are not going to make us blind overnight, but evidences are clear: a cumulative effect is present, and it is potentially dangerous. Voke, Optometry Today 21, 22 Meyenhofer, Klin Monatsbl Augenh 24, 49 Vogt, Arch.
Goldmann, Arch. Yu, et al. Pitts, and A. Salit, Acta Ophthalmologica 18, Okuno, Ann. Dis Primer 1, Lydhal, and B. Philipson, Acta Ophthalmologica 62, Gandolfo, A. Rindi, and D. Sliney Plenum Press, New York, , pp. Lambert, et al. Dadoukis, et al. Sivak, and M. The wavelengths associated with these injuries range between nm and nm. However, you should never stare directly into any light source, such as the sun or bulbs, for long periods of time because it can cause irreversible damage to the retina.
When you stare at a light source, the ultraviolet rays can harm the tissue of parts of the eye, like the retina. This is what happens when you stare directly at the sun and the short-term damage is called solar keratitis. Symptoms of solar keratitis include pain, inflammation, and light sensitivity. High-intensity damage caused by infrared light is called solar retinotopy which is the result of UV light burning holes in the retina part of the eye.
It causes central blind spots known as a scotoma. Intense infrared light can damage the eyes but studies show that the use of it can reverse the effects of light damage to the retina.
A treatment called red light therapy heals skin and muscle tissue. The red light distributes low levels of near-infrared light. This type of therapy is also known as low-level laser therapy LLLT , photobiomodulation, and low-power laser therapy. Red light therapy increases the healing process of people who have inflammation or damaged eyes. Read details. Natural light stimulates mitochondria in your cells which increases the production of Adenosine 5-triphosphate ATP. ATP is the molecule responsible for storing and transferring energy in cells.
Red light therapy fights against macular degeneration which optimizes the cells inside your eyes, even as you age. Therefore, high-quality red light therapy devices can deliver safe wavelengths of natural light to increase cellular energy production.
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