One of the most common concerns with red light therapy is the eye area. People want to use red lights on the skin of the face, but are worried that bright red light pointed there may not be optimal for their eyes. Is there anything to be worried about? Can red light damage the eyes? or can it actually be very beneficial and help to heal our eyes?
Eyes are perhaps the most vulnerable and precious parts of our bodies. Visual perception is a key part of our conscious experience, and something so integral to our day-to-day functioning. Human eyes are especially sensitive to light, being able to differentiate between up to 10 million individual colours. They can also detect light between the wavelengths of 400nm and 700nm.
We do not have the hardware to perceive near infrared light (as used in infrared light therapy), just as we do not perceive other wavelengths of EM radiation such as UV, Microwaves, etc. It has recently been proven that the eye can detect a single photon.1 Like elsewhere on the body, eyes are made up of cells, specialised cells, all performing unique functions. We have rod cells to detect light intensity, cone cells to detect colour, various epithelial cells, humor producing cells, collagen producing cells, etc. Some of these cells (and tissues) are vulnerable to some types of light. All of the cells receive benefits from some other types of light. Research in the area has increased significantly in the last 10 years.
Beneficial light for eyes
Most of the studies that point to beneficial effects use LEDs as the light source with the vast majority around the wavelength of 670nm (red). Wavelength and light type/source are not the only important factors though, as the light intensity and exposure time affect the results.
How does red light help the eyes?
Given that our eyes are the primary light-sensitive tissue in our body, one might think that the absorption of red light by our red cones has something to do with the effects seen in the research. This is not entirely the case.
The primary theory explaining the effects of red and near infrared light therapy, anywhere in the body, involves the interactions between light and the mitochondria. The core function of mitochondria is to produce energy for its cell – light therapy improves its ability to make energy.
The eyes of humans, and specifically the cells of the retina, have the highest metabolic requirements of any tissue in the entire body – they require a lot of energy. The only way to meet this high demand is for the cells to house many mitochondria – and so it is no surprise that cells in the eyes have the highest concentration of mitochondria anywhere in the body.
Seeing as light therapy works via interactions with the mitochondria, and the eyes have the richest source of mitochondria in the body, it is a reasonable assumption to hypothesise that the light will also have the most profound effects in the eyes compared to the rest of the body. On top of that, recent research has shown that degeneration of the eye and retina is directly linked to mitochondrial dysfunction. So a therapy that can potentially restore the mitochondria, of which there are many, in the eye is the perfect approach.
Best wavelength of light
670nm light, a deep red visible type of light, is by far the most studied for all eye conditions. Other wavelengths with positive results include 630nm, 780nm, 810nm & 830nm. Laser vs. LEDs – a note Red light from either lasers or LEDs can be used anywhere on the body, although there is one exception for lasers specifically – the eyes. Lasers are NOT suitable for light therapy of the eyes.
This is due to the parallel/coherent beam property of laser light, which can be focused by the lens of the eye to a tiny point. The entire beam of laser light can enter the eye and all of that energy is concentrated into an intense tiny spot on the retina, giving an extreme power density, and potentially burning/damaging after just a few seconds. LED light projects out at an angle and so does not have this issue.
Power density & dose
Red light passes through the eye with over 95% transmission. This is true for near infrared light and similar for other visible light such as blue/green/yellow. Given this high penetration of red light, the eyes only require a similar treatment modality to the skin. Studies use around 50mW/cm2 power density, with quite low doses of 10J/cm2 or less. For more information on light therapy dosing, see this post.
Harmful light for eyes
Blue, violet and UV light wavelengths (200nm-480nm) are bad for the eyes, being linked to either retinal damage or damage in the cornea, humour, lens and optical nerve. This includes direct blue light, but also blue light as part of white lights such as household/street LED bulbs or computer/phone screens. Bright white lights, especially those with a high colour temperature (3000k+), have a large percentage of blue light and are not healthy for the eyes. Sunlight, especially midday sunlight being reflected off water, also contains a high percentage of blue, leading to eye damage over time. Luckily the earth’s atmosphere filters out (scatters) blue light to some extent – a process termed ‘rayleigh scattering’ – but midday sunlight still has a lot, as does sunlight in space seen by astronauts. Water absorbs red light more so than blue light, so the reflection of sunlight off lakes/oceans/etc is just a more concentrated source of blue. It’s not just reflected sunlight that can do harm though, as ‘surfer’s eye’ is a common issue related to UV light eye damage. Hikers, hunters and other outdoorsmen can develop this. Traditional sailors such as old navy officers and pirates would almost always develop vision issues after a few years, mainly due to sea-sunlight reflections, exacerbated by the nutritional issues. Far infrared wavelengths (and just heat in general) can be harmful for the eyes, as like with other cells of the body, functional damage occurs once the cells get too warm (46°C+ / 115°F+). Workers in old furnace related jobs such as engine management and glass blowing always developed eye issues (as the heat radiating from fires/furnaces is far infrared). Laser light is potentially harmful for the eyes, as mentioned above. Something like a blue or UV laser would be the most destructive, but green, yellow, red and near infrared lasers can still potentially cause harm.
Eye conditions helped
General vision – visual acuity, Cataracts, Diabetic Retinopathy, Macular Degeneration – aka AMD or age-related macular degeration, Refractive Errors, Glaucoma, Dry Eye, floaters.
Using light therapy on the eyes before sun exposure (or exposure to bright white light). Daily/weekly use to prevent eye degeneration.
- Direct detection of a single photon by humans. Tinsley et al. 2016.
- Light transmission of the cornea in whole human eyes. Beems et al. 1990.
- Photostimulation of mitochondria as a treatment for retinal neurodegeneration. Beirne et al. 2017
- Light-Emitting Diode (LED) therapy improves occipital cortex damage by decreasing apoptosis and increasing BDNF-expressing cells in methanol-induced toxicity in rats. Ghanbari et al. 2017
- Aging retinal function is improved by near infrared light (670 nm) that is associated with corrected mitochondrial decline. Sivapathasuntharam et al. 2017
- Visual light effects on mitochondria: The potential implications in relation to glaucoma. Osborne et al. 2016
- Targeting mitochondrial function to treat optic neuropathy. Gueven et al. 2016
- Short-term effects of extremely low-frequency pulsed electromagnetic field and pulsed low-level laser therapy on rabbit model of corneal alkali burn. Rezaei Kanavi et al. 2016
- Red Light Treatment in an Axotomy Model of Neurodegeneration. Beirne et al. 2016
- Red light of the visual spectrum attenuates cell death in culture and retinal ganglion cell death in situ. Del Olmo-Aguado et al. 2016
- Photobiomodulation reduces drusen volume and improves visual acuity and contrast sensitivity in dry age-related macular degeneration. Merry et al. 2016
- Photobiomodulation for the treatment of retinal diseases: a review. Geneva II et al. 2016
- Optical monitoring of retinal respiration in real time: 670 nm light increases the redox state of mitochondria. Kaynezhad et al. 2016
- Near-Infrared Photobiomodulation in Retinal Injury and Disease. Eells et al. 2016
- Mechanistic Insights into Pathological Changes in the Diabetic Retina : Implications for Targeting Diabetic Retinopathy. Roy et al. 2016
- Efficacy of 670 nm Light Therapy to Protect against Photoreceptor Cell Death Is Dependent on the Severity of Damage. Chu-Tan et al. 2016
- Pre-exposure to low-power diode laser irradiation promotes cytoprotection in the rat retina. Sun et al. 2015
- Photobiomodulation with 670 nm light increased phagocytosis in human retinal pigment epithelial cells. Fuma et al. 2015
- Photobiomodulation Mitigates Diabetes-Induced Retinopathy by Direct and Indirect Mechanisms: Evidence from Intervention Studies in Pigmented Mice. Saliba et al. 2015
- Mitochondrial decline precedes phenotype development in the complement factor H mouse model of retinal degeneration but can be corrected by near infrared light. Calaza et al. 2015
- Helium-neon laser therapy in the treatment of hydroxyapatite orbital implant exposure: A superior option. Xu et al. 2015
- “Effects of Photobiomodulation Therapy on Patients with Primary Open Angle Glaucoma: A Pilot Study. [RETRACTED ARTICLE]Ivandic & Ivandic et al. 2015″
- “Aplication of low-level Laser therapy (LLLT) in patients with Retinitis Pigmentosa (RP) [Abstract]Koev K et al. 2015″
- Recharging mitochondrial batteries in old eyes. Near infra-red increases ATP. Gkotsi et al. 2014
- Protective effect of light emitting diode phototherapy on fluorescent light induced retinal damage in Wistar strain albino rats. Ahamed Basha et al. 2014
- Photobiomodulation in the treatment of patients with non-center-involving diabetic macular oedema. Tang et al. 2014
- Low-level laser therapy improves vision in a patient with retinitis pigmentosa. Ivandic & Ivandic et al. 2014
- Differential effects of 670 and 830 nm red near infrared irradiation therapy: a comparative study of optic nerve injury, retinal degeneration, traumatic brain and spinal cord injury. Giacci et al. 2014
- Combining neuroprotectants in a model of retinal degeneration: no additive benefit. Di Marco et al. 2014
- Treatment with 670 nm light up regulates cytochrome C oxidase expression and reduces inflammation in an age-related macular degeneration model. Begum et al. 2013
- The time course of action of two neuroprotectants, dietary saffron and photobiomodulation, assessed in the rat retina. Marco et al. 2013
- Paranode Abnormalities and Oxidative Stress in Optic Nerve Vulnerable to Secondary Degeneration: Modulation by 670 nm Light Treatment. Szymanski et al. 2013
- Low-intensity far-red light inhibits early lesions that contribute to diabetic retinopathy: in vivo and in vitro. Tang et al. 2013
- Laser photobiomodulation as a potential multi-hallmark therapy for age-related macular degeneration. Rodríguez-Santana & Santana-Blank et al. 2013
- Age-related retinal inflammation is reduced by 670 nm light via increased mitochondrial membrane potential. Kokkinopoulos et al. 2013
- 670nm photobiomodulation as a novel protection against retinopathy of prematurity: evidence from oxygen induced retinopathy models. Natoli et al. 2013
- 670 nm light mitigates oxygen-induced degeneration in C57BL/6J mouse retina. Albarracin et al. 2013
- 670 nm LED ameliorates inflammation in the CFH−/− mouse neural retina. Kokkinopoulos I et al. 2013
- “Two year follow-up of low-level laser therapy (LLLT) in patients with age-related macular degeneration (AMD) [ABSTRACT]Koev et al. 2012″
- Treatment with 670-nm light protects the cone photoreceptors from white light-induced degeneration. Albarracin & Valter et al. 2012
- Photobiomodulation in Inherited Retinal Degeneration. Gopalakrishnan S et al. 2012
- Low-level laser therapy improves visual acuity in adolescent and adult patients with amblyopia. Ivandic et al. 2012
- 670-nm light treatment reduces complement propagation following retinal degeneration. Rutar et al. 2012.
- 670 nm red light preconditioning supports Müller cell function: evidence from the white light-induced damage model in the rat retina. Albarracin R et al. 2012
- Photobiomodulation protects the retina from light-induced photoreceptor degeneration. Albarracin et al. 2011
- “He-Ne low level laser therapeutic applications for treatment of corneal trauma [Proceedings article]Koev et al. 2011″
- The influence of He-Ne laser on scar formation after trabeculectomy in rabbits. Hu et al. 2010
- Near-infrared light protect the photoreceptor from light-induced damage in rats. Qu et al. 2010
- Near infrared light reduces oxidative stress and preserves function in CNS tissue vulnerable to secondary degeneration following partial transection of the optic nerve. Fitzgerald et al. 2010
- Influence and mechanism of He-Ne laser on scar formation of filtration canal after trabeculectomy in rabbit. Wang et al. 2010
- He-Ne low level laser therapeutic applications for treatment of acute iridocyclitis. Koev et al. 2010
- Gene and noncoding RNA regulation underlying photoreceptor protection: microarray study of dietary antioxidant saffron and photobiomodulation in rat retina. Natoli et al. 2010
- Early diagnosis of ocular hypertension using a low-intensity laser irradiation test. Ivandic et al. 2009
- “[Effect of infrared low-intensity laser therapy on orbital blood circulation in children with progressive short sightedness]. [Article in Russian]Shurygina & Khadzhieva et al. 2009″
- Neuroprotective effects of near-infrared light in an in vivo model of mitochondrial optic neuropathy. Rojas et al. 2008
- Low-level laser therapy improves vision in patients with age-related macular degeneration. Ivandic et al. 2008
- GaAs laser treatment of bilateral eyelid ptosis due to complication of botulinum toxin type A injection. Majlesi G et al. 2008
- Increases in central retinal artery blood flow in humans following carotid artery and stellate ganglion irradiation with 0.6 to 1.6 microm irradiation. Mii et al. 2007
- Therapeutic photobiomodulation for methanol-induced retinal toxicity. Eells et al. 2003.
- “[Effects of low-intensity infrared laser irradiation on the eye (an experimental study)]. [Article in Russian]Prokof’eva et al. 1996″
- Ophthalmic effects of low-energy laser irradiation. Belkin & Schwartz et al. 1994
- Dose and temporal parameters in delaying injured optic nerve degeneration by low-energy laser irradiation. Rosner et al. 1993
- Low-energy laser irradiation–a new measure for suppression of arachidonic acid metabolism in the optic nerve. Naveh et al. 1990
- “[The stimulating effect of helium-neon laser radiation on rabbit eyes]. [Article in Russian]Sokolovskii et al. 1990″
- “[Laser irradiation: study of general and local mechanisms of its action in irradiation of the eyeball. An experimental study.]. [Article in Russian] Kiselev et al. 1990″
- Temporal parameters of low energy laser irradiation for optimal delay of post-traumatic degeneration of rat optic nerve. Assia et al. 1989
- “[The mechanism of action of laser stimulation of the eye]. [Article in Russian] Shmyreva et al. 1989″
- Effects of low-energy He-Ne laser irradiation on posttraumatic degeneration of adult rabbit optic nerve. Schwartz et al. 1987