{"id":9646,"date":"2024-08-28T16:54:37","date_gmt":"2024-08-28T20:54:37","guid":{"rendered":"https:\/\/www.vielight.com\/?p=9646"},"modified":"2025-08-26T10:57:05","modified_gmt":"2025-08-26T14:57:05","slug":"can-light-penetrate-the-skull","status":"publish","type":"post","link":"https:\/\/www.vielight.com\/blog\/can-light-penetrate-the-skull\/","title":{"rendered":"Can Light Penetrate the Skull?"},"content":{"rendered":"

Can light penetrate the human skull and reach the brain?<\/strong> This question often arises among both skeptics and scientists.<\/p>\n

The answer is yes <\/em>but with caveats; this requires an appropriate wavelength (nm) and sufficient irradiance (mW\/cm\u00b2) In this demonstration<\/a> with a real human skull, the Vielight Neuro<\/a>, emitting 810 nm near-infrared light at an industry-leading irradiance of 250 mW\/cm\u00b2, clearly passes through the skullcap.<\/p>\n

With the highest irradiance in the brain photobiomodulation field and the most published research in the industry, Vielight has set the benchmark for depth of penetration and the most published<\/a> brain photobiomodulation studies.<\/p>\n

Watch the video here:<\/strong><\/p>\n<\/div>

<\/lite-youtube><\/div><\/div>
<\/div><\/div>

Firstly, why deliver light energy through the skull?<\/h2>\n

The discovery that red to near infrared light energy produces beneficial effects within neurons is groundbreaking. Near-infrared light stimulates a photosensitive enzyme, cytochrome c oxidase, that\u2019s found within mitochondria \u2013 which leads to increased cellular energy, leading to a process known as “brain photobiomodulation”. By stimulating cytochrome oxidase activity, transcranial photobiomodulation<\/a> increases neuronal energy levels \u2013 leading to increased gamma brain oscillations, brain plasticity and cognitive flexibility.[1]<\/sup><\/p>\n

However, this non-invasive, chemical-free brain enhancing stimulation wouldn\u2019t be possible, if near infrared light energy couldn\u2019t reach the brain in the first place.<\/p>\n

\"\"

810nm light energy penetration through a human skull with the Vielight Neuro.<\/p><\/div>\n

What is near infrared light energy?<\/h2>\n

Near infrared light (NIR) energy is part of the electromagnetic spectrum \u2013 which are waves (or photons<\/a>) of the\u00a0electromagnetic field<\/a>, radiating through space, carrying electromagnetic\u00a0radiant energy<\/a>. At this day and age, several existing technologies depend on the ability of electromagnetic energy to penetrate solid objects. Several examples include WiFi, mobile data, radar and navigation satellites.<\/p>\n

<\/p>\n

Figure 1 <\/strong>The electromagnetic spectrum<\/p>\n

The depth or the power of penetration by light energy depends on the wavelength in the electromagnetic spectrum. Thus, the longer the wavelength, the greater the ability for photons to penetrate an object. For example, near infrared light is found around the center of the electromagnetic spectrum.<\/p>\n

\n

Does 810 nm or 1064 nm (1070nm) penetrate deeper into the brain?<\/h2>\n

According to\u00a0a transcranial brain photobiomodulation\u00a0(PBM) study by Harvard Medical School<\/a><\/strong>, Department of Psychiatry, the 810nm wavelength has been found to be superior to other wavelengths, which includes higher wavelengths in the 1070nm range for penetration and dosimetry.<\/p>\n

According to this study by Harvard Medical School, the order of penetration and dosimetry effectiveness is:<\/span><\/p>\n

    \n
  1. \n

    810\u202fnm<\/strong>\u00a0\u2013 consistently highest across all age groups and regions<\/span><\/p>\n<\/li>\n

  2. \n

    850\u202fnm<\/strong>\u00a0and\u00a01064\u202fnm<\/strong>\u00a0\u2013 next most effective in most cases<\/span><\/p>\n<\/li>\n

  3. \n

    670\u202fnm<\/strong>\u00a0and\u00a0980\u202fnm<\/strong>\u00a0\u2013 lesser deposition overall<\/span><\/p>\n<\/li>\n<\/ol>\n

    This Harvard study is also supported by\u00a0another brain PBM dosimetry study<\/a>\u00a0by leading Chinese universities, comparing 660 nm, 810 nm, 880 nm and 1064 nm. They discovered that the distribution of photon fluence at 660 and 810\u2009nm within the brain was much wider and deeper than 980 and 1064\u2009nm.<\/p>\n

    \n\"\"<\/picture>\n

    The distribution of photon fluence at 660 nm, 810 nm, 980 nm and 1064\u2009nm. Wang P, Li T. \u201cWhich wavelength is optimal for transcranial low-level laser stimulation?\u201d J. Biophotonics. 2019; 12:e201800173. https:\/\/doi.org\/10.1002\/jbio.201800173<\/p>\n<\/div>\n

    The differences in dosimetry is supported by a well-established biological principle, the\u00a0body\u2019s first optical window<\/a>. While, the 1064 and 1070nm wavelengths are longer and scatter less than 810nm, they are more\u00a0strongly absorbed by water<\/a>, which is abundant in biological tissues. This increased absorption by water can lead to reduced photonic availability and tissue penetration despite the longer wavelength, which the\u00a0Harvard Medical study<\/a>\u00a0and\u00a0Peking Medical University study<\/a>\u00a0reveal.<\/p>\n

    \n\"\"<\/picture>\n

    The near infrared window or body\u2019s optical window. Image source: Wang, Erica & Kaur, Ramanjot & Fierro, Manuel & Austin, Evan & Jones, Linda & Jagdeo, Jared. (2019). Safety and penetration of light into the brain. 10.1016\/B978-0-12-815305-5.00005-1.<\/p>\n<\/div>\n