May 08, 2020
3 min read

BLOG: The blue light effect you probably never thought about

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Robert S. Fox, OD, FCOVD, FCSO
Robert S. Fox

by Robert S. Fox, OD, FCOVD, FCSO

You may have heard about the benefits of blue light-filtering glasses to prevent eye strain during digital device use or the debate about whether blue-light blocking IOLs can protect against age-related macular degeneration.

Specialized therapy with blue light can also stimulate the parasympathetic nervous system when it is has been disrupted by a traumatic brain injury.

In a healthy brain, the two parts of the autonomic nervous system, the parasympathetic and sympathetic nervous systems, are in balance. Under stress, the sympathetic nervous system is activated by adrenaline. When this happens, the individual struggles to use their peripheral vision to process information and their visual space becomes “tunneled.” After a traumatic brain injury (TBI), the sympathetic nervous system goes into overdrive, and the patient is stuck in fight-or-flight mode. Their sleep is disrupted, and they may experience any number of visual symptoms, including poor focusing, poor convergence, exotropia and problems with binocularity.

To help treat these and other visual conditions, I use syntonics — or optometric phototherapy— to apply different frequencies of light to effect changes in the autonomic nervous system. When I first learned of this approach, I was extremely skeptical. As an engineer, I didn’t think it would work, and as an optometrist, I wasn’t sure it was in my wheelhouse, even if it did. But I also needed more tools in my toolbox to treat patients with TBI.

Today, there is increasing evidence that syntonics can be a beneficial part of the TBI recovery process (Raikes et al.). In a recently published randomized, double-masked, controlled trial, researchers compared the effects of 6 weeks of daily, 30-minute sessions of pulsed blue (469 nm) or amber (578 nm) light in adults with a recent TBI. The blue light improved the patients’ sleep patterns and executive functioning, as well as neuroimaging markers of brain health, such as increased volume of the posterior thalamus, and greater thalamo-cortical functional connectivity (Killgore et al.).

In my practice, syntonics is typically used in conjunction with other treatments. For example, vision therapy sessions can often be exhausting and uncomfortable for patients with TBI because the therapy itself provokes symptoms. A few minutes of syntonics at the end of the vision therapy session can reduce the discomfort and speed recovery. I also often prescribe a few weeks of syntonics before beginning vision therapy, as I find that it helps to expand patients’ peripheral visual field, reduce light sensitivity and help patients experience more success with their vision therapy. While colors at the blue end of the spectrum are most beneficial for TBI treatment, colors at the red end of the spectrum can be very useful for treating amblyopia or esotropia.

In-office syntonics instruments, in which the patient looks through a long tube that blocks out ambient and peripheral light, are the most effective, in my experience. These typically offer a wide variety of high-quality color filters and a controlled light source. At-home units and syntonic goggles are also available and may be valuable as a starting point or to supplement work done in the office.


Killgore WDS, et al. Neurobiol Dis. 2020;doi:10.1016/j.nbd.2019.104679.

Raikes AC, Killgore WDS. Concussion. 2018;doi:10.2217/cnc-2018-0006.

For more information:

Robert S. Fox, OD, FCOVD, FCSO, has a practice in Latham, N.Y., that is limited to developmental and rehabilitative optometry. He is the president of the College of Syntonic Optometry and has previously served as chair of the College of Optometry in Vision Development International Examination and Certifications Board, as well as on the professional advisory committee of the Brain Injury Association of New York State.

Disclosure: Fox reports no relevant financial disclosures.

Disclaimer: The views and opinions expressed in this blog are those of the authors and do not necessarily reflect the official policy or position of the Neuro-Optometric Rehabilitation Association unless otherwise noted. This blog is for informational purposes only and is not a substitute for the professional medical advice of a physician. NORA does not recommend or endorse any specific tests, physicians, products or procedures. For more on our website and online content, click here.