Avoiding Cataracts from Near Infrared Light: Eye Safety Calculator
“Those who look with clouded eyes see nothing but shadows” – FF7R
Eyesight is often rated as our most valued sense.
A 2016 US survey study in JAMA found that Losing Eyesight is a bigger concern than Memory Loss, Losing a Limb, or losing hearing or speech. [1] Participants were more concerned with getting Blindness than Alzheimer’s, Cancer, or Heart Disease. [1]
A recent 2019 UK survey in JAMA also confirmed that vision was voted the most important sense. [2] They learned that people would rather live a shorter life with good eyesight, than to live longer without eyesight. [2]
Obviously, many people have an irrational fear that they would prefer Heart Disease, Alzheimer's, or even Death over living with Blindness.
To support eye health, many people are rightfully aware that Red and NIR light therapy is an obvious clinically-studied method to support the mitochondria of the eye.
Conversely, there is still lingering fear that Near Infrared (NIR) light, and Infrared light in general, may be causing an insidious gradual progression of cataract formation.
The confusion and dual nature of NIR on the eyes would incite enough fear for people to avoid the potential benefits of NIR completely from red light therapy devices.
So once again we look at the science and official guidelines so that we can be well-informed and make reasonable decisions for eye health and safety.
Epidemic of Cataracts:
A cataract is a condition where the lens of the eyes becomes clouded, reducing vision and causing blurriness. The proteins in the lens of the eye have broken down and clump together.
The NIH estimates that more than half of adults over the age 80 will have or have had cataracts. Indeed, cataract surgery is one of the top operations conducted in the USA.
The NIH also lists some of the top contributing factors to developing cataracts including:
- Diabetes, Alcohol, and Smoke
- Eye Injury, Steroid Medications, and Family History of Cataracts
- High Sun Exposure
The mainstream list of causes of cataracts do not directly mention infrared light as a factor.
So where has this fear of infrared light causing cataracts come from? Is it relevant to Near-Infrared LED light therapy panels?
Let’s take a look at the mechanisms, history, current science, and relevant exposures that infrared could be impacting the eye.
Summary:
Here are the top reasons as to how and why infrared light, particularly Near-Infrared (NIR), is associated with cataract formation.
- NIR between 780-1400nm is considered a main culprit for potential damage because it passes the cornea and is absorbed by the iris and partially by the lens of the eye. [10]
- Gradual damage occurs from NIR exposure leading to delayed-onset cataracts decades later.
- NIR LEDs are a “new” technology that long term safety studies have not been conducted on human eyes.
- NIR alone is invisible which the eye will have a wider retina opening and no aversion reflex.
And the research we found on these topics:
- While NIR does get absorbed by the lens and surrounding iris, there are always confounding factors causing damage like excessive doses, high temperature environments, far-infrared intensity causing heat, and even smoke or poor air quality. [6]
- The gradual damage theory was debunked in a research trial that used high intensity NIR laser but controlled for temperature – they found no sign of cataract from NIR exposure. [9]
- Near-Infrared exposure to the eyes is not “new” to humans in any sense, from sunlight to fireplaces to incandescent lighting and infrared heaters. NIR is natural and well tolerated by human and animal eyes when used responsibly. As well many safety assessments have been conducted for NIR LEDs in security cameras, retinal scanners, and other invisible sensors.
- While NIR alone can be a risk, it is best used with Red light in Red Light Therapy panels to make sure there is brightness for people to use good judgement to avert their eyes. A user would normally feel heat on the face if there was excessive intensity and know to pull away.
Conversely, the positive benefits of low-intensity NIR light to the eye should not be overlooked and will be reviewed at the end.
Disclaimer: There are many other eye hazards to watch out for, particularly acute damage caused by high-intensity collimated beams like from a laser or narrow beam angle lenses, and other high-risk wavelengths for the eyes like UV and Blue light. So, we should always be responsible with our eye exposure to light, check with your doctor about photosensitivity or pre-existing conditions, and understand the safety guidelines from individual device manufacturers.
Scope: In this blog we are only investigating if we can be absolutely certain that even low-level NIR exposure from LEDs does not cause a gradual formation of cataracts.
The Bottom Line: How Much Intensity of NIR is Safe?
Several studies and guidelines have stated that a NIR exposure intensity to the eye of up to 10mW/cm^2 has no risk of cataract formation especially for long-term chronic (daily) exposure over 1000 seconds (16.67 min). [3][4][6] The ICNIRP notes that higher intensities than 10mW/cm^2 are safe for shorter time periods or in cold environments.
They specifically note the guidelines are set to avoid cataractogenesis (formation of cataracts):
"To avoid thermal injury of the cornea and possible delayed effects on the lens of the eye (cataractogenesis), infrared radiation (770 nm - 3 m) should be limited to 100 W/m^2 (10 mW/cm^2) for lengthy exposures ( >1,000 s), and to 1.8 t^3/4 W/cm^2 for shorter exposure durations" [4]
To be clear these guidelines are intended to include incoherent (non-laser) exposures to near-infrared light including incandescent bulbs, infrared heaters, industrial furnaces, and LEDs. And this calculation is for Cornea and Lens safety only and they have other calculations for different wavelength ranges and different parts of the eye.
For shorter exposure times less than 1000 seconds, they give us this formula such that higher intensities can be tolerated according to the guideline.
E < 1.8 (t) ^-3/4 (W/m^2)
From this calculation we can find that 100mW/cm^2 can be tolerated for up to 47 seconds before potential damage could occur according to the ICNIRP.
Other researchers have noted that 100mW/cm^2 of NIR would not cause significant temperature increase in the eyes to cause damage, but the ICNIRP comments that such a high intensity from an incoherent source is impractical because it would felt as “painfully warm” on the face. [3] [5][16]
"Vos and van Norren (1994) argued that an irradiance of 1 kW mj2 would not increase the temperature of the anterior segment of the eye by more than 1-C.
However, 1 kW mj2 on the face would be painfully warm and not tolerated in a warm environment."[16]
Good thing nobody makes “painfully warm” intensity panels that emit >100mW/cm^2 at 6 inches away. However, feeling too much heat on the face is a good warning to move further away, and we are reassured by this data that we don’t immediately get damage from such a high exposure.
Eye Safety Calculator:
Based on the ICNIRP equation above, we made this calculator to enter in the intensity of your device to tell you the amount of exposure time that is generally safe for the eyes in the NIR range according to ICNIRP guidelines.[4]
We recommend using the total combined intensity of both Red and NIR for added safety since even Red light can contribute to the total heat load on the eye.
We don't recommend "testing" the limits of this calculator on yourself, but remain well below the levels of either intensity or time as noted by these ICNIRP equations. Use our other eye safety tips in another blog for simple ways to use red light therapy panels responsibly.
Always check with your doctor if you have any pre-exisitng conditions or medicines that would cause photosensitivity which would mean certain individuals would need to be even lower exposures than the general guidelines here.
Glassblower NIR Exposure:
Where did the fear of Near-Infrared and Infrared light causing cataracts come from?
There is a long history of cataracts in glassblowers, steelworkers, metalworkers, welders, and other workers in hot environments near furnaces and kilns that are emitting infrared, even documented back to 1739. [6]
However, several articles including one from Nature persistently note that there is a thermal or heating component, high temperature environments, a lot of Far-Infrared, exposure during an entire work shift (8 hours); such that the damage is never from NIR alone and from excessive exposure. [6] [7]
One study measured the daily Infrared radiation exposed to glassblowers working near the furnace. Those glassblowers were exposed to 2000-3000 J/cm^2 per day, an estimated 40-80 mW/cm^2 every day for 10-15 years to develop cataracts (and only 10% of that total IR is estimated to be IR-A Near-Infrared). [6]
This is a tremendous amount of dosage that you would never get from responsible use of a LED panel. Even a high intensity hot-spot of a panel may produce up to 80mW/cm^2, but even if there is 20 minutes of direct exposure to the face that would be only 96 J/cm^2, which is less than 5% of the exposure given to glassblowers every day.
However, that same article aptly titled "Determination of infrared radiation levels for acute ocular cataractogenesis" published in 1981 mentions from their research that the 10mW/cm^2 standard could be higher.
"The data in this study indicate that the 10mW/cm^2 figure is conservative and could be increased. We recognized that ACGIH recommendations are intended for delayed effects of chronic exposure while the data of this study concern from acute exposures; however, we are certain that our exposures were only to IR...." [6]
So we can appreciate that even in the early 1980's research has been conducted on this topic, and they were also aware of a potential "delayed effects" which would be the gradual building of cataracts. However, these researchers did not seem concerned by relatively low intensities in normal environments.
Gradual Degradation Theory - Debunked
UV and Blue light are regarded as causing a gradual degradation of the lens by a photochemical effect. [8] Where UV and Blue are shorter wavelength and higher frequency photons that will slowly accumulate the damage on the lens. Eventually leading to the age-related cataract formation.
The hypothesis has been that Near-Infrared light may have the same effect, that it is a slow accumulation of damage associated with long-term chronic low-dose exposure.
That is to say, even if we stay below non-thermal exposures recommended by the ICNIRP to the eye; there still could be a very slow progression of lens degradation that would manifest decades later as Cataracts.
The theory is summarized well in this quote:
"If IRR causes damage photochemically, repeated below threshold exposures could accumulate over time to cause cataract." [11]
This appears to be the real fear of NIR - since it is a slow, insidious, unmeasurable gradual progression of the disease state until it is too late.
In a recent 2015 experiment, researchers put this hypothesis to the test. They exposed rat eyes to a NIR laser of 1090nm at 96 W/cm^2 (yes, 96,000 mW/cm^2 intensity). They controlled the exposure so the lens temperature would not exceed 8 C. In this experiment, they found no signs of cataract formation, even at such a excessively high intensity of Near-Infrared light. [9]
This means there is no gradual accumulation of cataract from high intensity NIR in a controlled trial. The authors concluded that they debunked the theory of a photochemical effect from NIR, but it is only a thermal effect if there is excessive heat or intensity for too long.
The article in Nature titled "Does infrared or ultraviolet light damage the lens?" comments on this great experiment, but recommends that more wavelengths and experiments should be conducted. [11] Which of course there should always be more experiments to keep confirming that the lens damage is a thermal effect and not a cumulative photochemical effect.
Everyday Infrared Exposure – Is the Risk Unavoidable?
The rumor persists that Near-Infrared LED technology is “new” to human existence. That perhaps long-term safety analysis has not been assessed.
Security cameras often have Near-Infrared LEDs that are useful for the "night vision" survalence. Could these also be a risk to the eyes?
This of course is also a false rhetorical argument; humans have been exposed to infrared light for eons both indoors and outdoors:
- About 32% of sunlight intensity is NIR from 780-1400nm, so on an average day that is 32mW/cm^2 that we would have been evolved to tolerate. Particularly in the sunrise and sunset there is proportionally more Red and NIR light that is in-line with the eye at the horizon.
- Fire, Stoves, and Furnaces emit a majority of intensity as infrared rays and heat - which have been an imporant part of human cultural expansion.
- Incandescent bulbs emit ~36% of it’s intensity as NIR which have been the primary source of lighting in homes for nearly a century.
- Infrared Heaters like Quarts Heaters are common space heaters and patio heaters and emit 42% NIR rays. [12]
- Security cameras often use 850nm or 940nm NIR LEDs for night-vision and are rapidly being installed everywhere.
- New iPhone scanning technology uses NIR LEDs, and other retinal and face scanners use NIR LEDs.
- The earliest household NIR LED was implemented in TV Remote controls in the 1950’s.
- All objects above 0 Kelvin (absolute zero) emit infrared light according to Planks Law. Everything is infrared all the time.
Clearly near-infrared light has been a natural part of human evolution, society, and even modern indoor lifestyles. Near-Infrared wavelengths are ubiquitous and unavoidable and there is nothing new about it to human or animal existence.
To fully avoid all Near-Infrared exposure, one would need to wear high-end laser goggles all the time. Especially outdoors.
So, if people are fearmongering that infrared light causes cataracts, just ask them if they are wearing Welding Goggles or NIR Laser Goggles all day every day, both indoors and outdoors (normal sunglasses aren't rated to block IR). If not, then they clearly don’t understand the science or they are simply hypocrites.
Cataracts and Sunlight
Sunlight has long been associated as a major risk factor for cataracts.
Many studies have surveyed populations of people to correlate lifetime sunlight exposure to cataracts. Here are just 6 of them.
However, the common knowledge is that the shorter UV (Ultraviolet) wavelengths of light are the main cause of cataracts from sunlight, due to the gradual photochemical breakdown we mentioned eariler.
This is why sunglasses are actually regulated by the FDA to ensure they properly block UV as advertised, yet there are no requirements or guidlines for sunglasses to block any form of infrared. Which reinforces that there is no mainstream acceptance that everyday levels of NIR does not cause direct eye damage, which if that were the case sunglasses would need to block NIR too.
Indeed, we reviewed 6 studies above on associations of Sunlight and cataracts, and not a single one even mentioned that Infrared light had any contribution to the condition, despite the large amount of NIR we know is emitted by the sun.
The study titled "Determination of infrared radiation levels for acute ocular cataractogenesis" comments on the studies comparing Sunlight to Cataracts:
"If sunlight were a causative agent, UV radiation would necessarily be implicated..."[6] The same study observes many early researchers used Xenon and Carbon Lamps which erroneously reported cataracts from the IR but there is massive UV exposure also from those types of lamps. [6]
But once again we can be comforted that our human eye can certainly tolerate the intensity of NIR from the sun (but never stare at the sun) of about 32mW/cm^2. An early estimation assumes that 10mW/cm^2 is natural from sunlight (because we have eye sockets and eyebrows and eyelashes and aversion reflexes that ensure we get indirect exposure). [3]
Which may play into the prevalence of this 10mW/cm^2 as being a safe level of NIR exposure for the eyes amonst these studies - because it is presumed to be a natural ambient level.
Cataracts from Security Cameras, IR Scanners, and Remote Controls
The article in Nature notes the obvious concern that the implementation of NIR LEDs in all facets of modern life is a new potential threat to the eyes.
“The current frequent use of near IRR for remote control and sensing demands verification that near IRR does not cause cataract photochemically. If IRR causes damage photochemically, repeated below threshold exposures could accumulate over time to cause cataract.” [11]
The modern world is increasingly using NIR LEDs for security cameras, face and eye scanners, remote controls, and other invisible sensor applications.
An important article on this topic is titled "Eye Safety Related to Near Infrared Radiation Exposure to Biometric Devices" and investigates this concern even in the year 2011. [13]
Ultimately they conclude that guidelines such as from the ICNIRP and IEC must be followed to prevent eye risks, as well they state that the current LED technology (in 2011) is not powerful enough to cause much risk to the eyes. [13]
However, this article had the foresight to note that the power of LEDs is increasing exponentially over time, as well arrays of LEDs (i.e. LED panels) would increase the intensity and potential risks. [13] So now in the year 2022 we should consider the serious risks of utilizing "the highest intensity" panels as a marketing gimmick that ignores safety for sales.
NIR Light Therapy Benefits Cataract Patients
An old article from Dr. Mercola’s website reviewed how Near-Infrared light is beneficial to the mitochondria in the human eye. He argued that the removal of incandescent lighting being replaced with blue-rich LEDs devoid of NIR was a main culprit of modern eye problems. So we can appreciate a reversal of perspective, that he is promoting more NIR exposure to the eye by switching back to incandescent bulbs in the house. A copy of the article was found here: https://globalpossibilities.org/how-led-lighting-may-compromise-your-health-2/
Indeed, a recent 2021 article titled “Near Infrared (NIR) Light Therapy of Eye Diseases: A Review” was resoundingly positive towards the use of NIR to support eye health through all of the same mechanisms that we understand Red Light Therapy benefits the mitochondria. [14]
Cells with the most mitochondria are highly responsive to Red and NIR light therapy. However this also means they will reach a biphasic dose response sooner so lower intensities and doses are required. This is usually mitigated by the skin for other organs, but eyes can get direct exposure.
The article concludes that NIR LEDs are safe and beneficial by saying “Nevertheless, LEDs only produce negligible heat, impossible for thermal injury”. [14] However, this statement assumes that medical devices are not making recklessly high intensity products and that the consumer is aware to avoid heating devices for the eyes.
A 2008 study on Age-related Macular Degeneration (AMD) recruited 193 patients that had cataracts and treated them with a NIR laser of 780nm. [15] Which of course would be contraindicated and unethical to treat people with cataracts with NIR laser according to the myths we have covered so far. Luckily, the researchers don’t listen to fearmongers on social media, and 95% of the patients with cataracts reported improved visual acuity from the study treatment with Near-Infrared laser light.[15]
Conclusions:
Eye health and eye safety of course is one of our top priorities especially since it is often rated as the most important human sense. Unfortunately the extreme fear of losing eyesight can make our minds clouded from the real rational science.
The industrial revolution had workers exposed to massive levels of heat, infrared, and NIR light for many hours a day without much protection or restrictions. Some were quick to place the blame entirely on the NIR exposure as causing cataracts in those industries.
One review notes that by the 1920's safety standards had improved such that:
"workers in the "heat industries" show equal or fewer cataracts than control population". [6]
We can even appreciate that perhaps lower, controlled exposures to NIR in these industries now potentially have "fewer cataracts" than the control population.
The research is positive that low-intensity Red and NIR light on the eyes is beneficial to the mitochondria and general eye health.
Like all things, the dose makes the poison. Drinking too much water will kill us, inhaling too much oxygen will kill us. Yet we critically need those things to survive.
Like water and oxygen, Near-Infared light has been a natural part of life since organisms manifested in the primordial goo. Humans clearly require NIR light for proper mitochondrial function especially in the eyes, but like all things we need moderation.
Many reports and guidelines show the human eye can tolerate up to 10mW/cm^2 for an infinite amount of time without any risk of damage. However, this may be an overly conservative estimate and we can likely tolerate higher intensities for short timeframes in cool environments.
An ancestral perspective of NIR exposure would make the threshold of closer to 30mW/cm^2, where sunlight, fire, and even incandescent bulbs have rarely been blamed for causing cataracts (from the infrared component).
While intensities up to 100mW/cm^2 may not be immediately dangerous to the eyes, we don’t want to push our luck with “painfully warm” intensities that wouldn’t benefit us anyway due to the dose-rate response. A heating sensation on the face and eyes is a good indication to move further away or to use eye protection.
As always, having realistic and honest intensity data is the first step towards responsible, safe, and effective red light therapy usage. Note that these safety guidelines are all based on Intensity so it is imperative that responsible manufacturers disclose thier actual intensity numbers to the consumer.
Listen to the guidelines from your device manufacturerers if they require goggles or protective eyewear during usage for their products, especially for high-intensity panels or lasers. However, we feel when people are properly educated about the risks - they will be more compliant to wear the neccesary safety gear.
And we are continuously re-examining the literature for safety guidelines that we can always offer you the best education for awareness to make smart choices for your eyes and body.
Disclaimer: This article is for education purposes only and does not provide medical advice for the treatment, diagnosis, or prevention of disease. Consult with your doctor and qualified professionals before implementing any of the information contained in this blog.
References:
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