Are your eyes sensitive to light … or just blue light!?

Eyes sensitive to light!? Evidently I am talking about light sensitive eyes as in photophobia, light aversion, discomfort glare, pain, eye fatigue and computer eye strain induced by light and glare. Increasingly scientific evidence shows that eye sensitivity to light tends to be caused only by a small portion of visible light that carries most of its energy – blue light, i.e. High Energy Visible (HEV) light. This article:

  • highlights key scientific reports indicating that eye sensitivity to light tends to be caused by blue light
  • suggests a way to test if and to what extent your eye sensitivity to light is blue light induced
  • proposes solutions to help you improve your light sensitivity pain threshold and/or cope with your blue light sensitive eyes

 

Eyes sensitive to light: My Christmas lights accident

I’d known for some time that I had eyes sensitive to light. No need to be more specific, right? Wrong!

It does help to know the underlying cause of eye sensitivity to light to fight it.

Eyes sensitive to light - christmas red and blue lightsWhat got me intrigued about blue light was an accident with Christmas tree lights. Until a couple of years ago we’d only used red lights. Then we decided to use blue ones. As far as my light sensitive eyes go it was a terrible mistake. Blue glare immediately felt uncomfortable to my eyes and my head. I couldn’t stand having the lights within my filed of vision. It was even worse in the dark (only with blue lights on). My eyes were fatigued no matter where I looked  although the blue glow was relatively weak.

That’s strange, I thought, because previously I’d had no problems with the old, red lights. So I decided to change them and… Voila! I could stare directly into the red lights, in the dark!, and felt no eye fatigue whatsoever.

That made me curious: are my light sensitive eyes in reality sensitive just to blue light?

 

Research: Not eyes sensitive to light but eyes sensitive to BLUE light

Very briefly, this is what you can find in scientific reports. It is not that clear-cut and simple, but to a large degree it is true: For most of us eye sensitivity to light (light and glare induced visual discomfort and pain) tends to be principally (not exclusively) due to blue light. More specifically, eyes sensitive to light tend to have deficient macular pigment which is our natural, internal blue light filter.

 


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Bluer indoor lighting tends to increase visual discomfort – eye strain

Cooler, more bluish, light (~5500-6500K when compared to warmer light ~2700-3500K) tends to be more uncomfortable causing eye fatigue and other eye strain symptoms. The severity of symptoms constitutes a continuum, such that some people are affected much more than others. It’s been estimated that 5-12% of the population suffers from visual stress that, in many -but not all- cases may be releived by reducing the amount of blue light (Levels of visual stress in proficient readers: Effects of spectral filtering of fluorescent lighting on reading discomfort; 2015. Spectral filtering of fluorescent lighting: Effects upon reading and visual discomfort in slow readers; 2012).

Eyes sensitive to light FLUORESCENT COLOR TEMPERATURE AND SPECTRAL POWER DISTRIBUTION

Spectral Distribution of Fluorescent Lamps (source). As light is cooler, bluer – its Correlated Color Temperature (CCT) increases from: (a) 3,000 K; (b) 4,000 K; (c) 6,500 K, the energy emitted by a fluorescent light source shifts from longer wavelengths (red) to shorter wavelengths (blue part of the spectrum).

 

Light sensitive eyes LED COLOR TEMPERATURE VS SPECTRAL POWER DISTRIBUTION NORMALIZED

Spectral power distribution of LED lamps (source). As LED lamp emits cooler, more bluish light – High Correlated Color Temperature (CCT), most of the energy emitted shifts towards the blue region, i.e. below ~500nm.

 

Greatest eye sensitivity to light induced pain is in the blue range

The TOO BRIGHT!! signal is transmitted to our brain via a special type of neurons found in eye’s retina (intrinsically photosensitive Retinal Ganglion Cells – ipRGCs) that are light sensitive themselves, particularly in the blue range, peak at ~480nm (ipRGCs are the primary but not exclusive circuit for light aversion; 2012).

Light sensitive eyes spectral sensitivity of human ipRGCs

Normalized spectral sensitivity curve of human ipRGCs. Adapted from (On Seeing Yellow: The Case for, and Against, Short-Wavelength Light–Absorbing Intraocular Lenses; 2012).

 

Different individual thresholds of eye sensitivity to light are due to different blue light filtering capacities of macular pigment

One of the functions of Macular Pigment is to block blue light (see below). It’s light absorption is the highest near ~460nm and drops to zero by ~530nm (The Visual Effects of Intraocular Colored Filters; 2012).

Light sensitive eyes macular pigment spectral absorption curve

Macular pigment absorbs blue light considerably more than other visible light wavelengths – peak ~460nm (Macular pigment densities derived from central and peripheral spectral sensitivity differences; 1998).

 

Eyes with low MPOD (macular pigment optical density), i.e. macular pigment’s poor blue light filtering capacity – are more sensitive to light. Hence, low MPOD means lower threshold to light induced pain (Action spectrum for photophobia; 2003. Macular pigment optical density and photophobia light threshold; 2006).

In some people macular pigment can filter as much as 10 times less blue light than in others (Individual variations in the spatial profile of human macular pigment; 1997) and it tends to decline with age (Resonance Raman Measurement of Macular Carotenoids in Normal Subjects and in Age-related Macular Degeneration Patients; 2002) … see images below.

eyes sensitive to light-macular pigment variability in bluelight filtering

3-D representations of different MPOD profiles – blue light absorption levels (source).

 

eyes sensitive to light-macular pigment bluelight filtering statistics

Estimated distribution of MPOD score in US population. Note that on average macular pigment lets past it 31% of blue light, and in many people much more than that. Only in about 22% of the population MPOD is sufficiently high to transmit 18% of blue light through to the photoreceptors at the macula. (Source)

 

To summarize, scientists have approached the issue of eyes sensitive to light from different fields. They appear to be converging on the theory that eye sensitivity to light is primarily a matter of blue light sensitivity which depends on the capacity of each person’s macular pigment to filter blue light.  Before suggesting some solutions let’s take a look at a simple way to check if and how sensitive to blue light your eyes are.

 

How can you know if your eye sensitivity to light and glare might be caused by blue light

There is an easy and free test of eye sensitivity to blue light. Download and install f.lux blue light filter app. F.lux allows you to increase and reduce the intensity of blue light emitted by your screen (see images below) with minimal detriment to contrast.

Light sensitive eyes - efficiency NO FLux Spectrographic analysis Light sensitive eyes - efficiency FLux at 2700K Spectrographic analysis Light sensitive eyes - efficiency FLux at 1200K Spectrographic analysis

(a) high blue peak: 6500K setting – f.lux filter OFF, (b) reduced blue peak: 2700K setting (70-80% of blue light filtered), and (c) minimal blue peak: 1200K setting (94-98% blue light filtered). If you use f.lux default settings your “white” background will look like it does in the image (a) during the day and look closer to image (b) at the beginning/end of the day and at night. This is because f.lux app was designed to address the problem of sleep disorder and not to solve the eye sensitivity to light problem. (Click on images to see more detail).

 

(1) Set f.lux to the lowest lighting setting, e.g. 2700K (see red arrows in the image below). Do this for both “Daytime” and “At night” to keep your screen always at the same, warmer, color temperature. At this setting blue light emissions are reduced by about 70-80%).

eyes sensitive to light - flux test

For this window to appear click on the f.lux icon on your task bar and then click on the button “Settings”.

 

If you feel immediate relief from eye strain in your eyes, than blue light is most likely the cause of your sensitivity to light.

 

(2) If after carrying out (1) you don’t feel an immediate improvement in your eyes, try working with f.lux running with the same settings as in (1).

After a day or two check the box “Disable for an hour” (see orange circle in the image above). If you find the change (more vivid, cooler and bluish colors) disturbing, more uncomfortable, your eye sensitivity to light is likely induced by blue light. However, your eyes are probably less blue light sensitive than if you feel much better immediately after  (1).

 

(3) If you felt uncomfortable or annoyed by the yellowish look of your screen with f.lux running, or if you haven’t noticed any difference in your visual comfort after (1) and (2), than the cause of your light sensitivity may be other than blue light.

You may continue your search for your perfect (least eye straining) color here. You might also consider intuitive colorimetry to determine what specific tint would make your eyes sensitive to light feel better.

 

How sensitive are your eyes to blue light

To figure out the level of your eye sensitivity to blue light try adjusting the lighting settings in f.lux (red arrows in the image above). The more you need to reduce screen’s blue light emissions (move f.lux lighting setting sliders left) to feel comfortable, the more sensitive you are.

 

What can you do if you have blue light sensitive eyes

Once you’ve pinpointed the root cause of your eye sensitivity to light it is easier to find solutions.

 

Improve your macular pigment blue light filtering capacity

Macular pigment optical density can be improved in most cases through diet. This may be by far the best solution. Read more about it in this post.

If you prefer taking macular pigment supplements to eating lots of green leafy vegetables you may buy them on Amazon (disclosure: commission link).

 

Protecting eyes sensitive to light outdoors – mind your lens tint color

Not all sunglasses lens colors are equally effective in filtering blue light outdoors. You can find more on this in this post.

 

Block blue light from indoor lighting

Wraparound eyewear recommended in the this post will be effective if you happen to spend considerable amount of time under cool, bluish fluorescent and LED lamps.

See also the post addressing blue light in fluorescent (and LED) lighting.

 

Shield your eyes from blue light emitted by digital display devices

See 13 Blue light screen filters: Specs and recommendations.

Check also this list of 10 different blue light filters to combat computer eye strain.

 

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4 Comments

  1. I’m sensitive to blue light. Pigmentation deficit has been long documented, just never made the connection to the sensitivity, or was never told I would be! Since I work on computers with multiple monitors usually upwards to 4, I have major eye strain and headaches almost, my simple solution was to custom preset each monitor removing Blue! Luckily color accuracy is not something my job is concerned with.

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    Reply

    1. Javier, that is definitely a good option to reduce blue light to the bare minimum your screens are capable of. Thank for pointing it out!

      (Judging from your comment I suppose you probably already know what I am about to write, but I’ll do it anyway in case it benefits other visitors in the future).

      Most screens will emit some blue light no matter what software manipulation you carry out. For example, when displaying colors that in theory shouldn’t contain any blue light (such as black -rgb:0,0,0, or red -rgb:255,0,0).

      The easiest way to see this is to set your screen to display black only and make the room dark (it is simple at night, just turn off the lights). You’ll see a blue glow comming out of your screen.

      If you want to get rid of all blue light what you need to do is either to:
      – install a good blue light filter screen (not too many arround – see this post) or,
      – get a good pair of blue blocking glasses (see this post)

      But careful, always pay attention to the spectrograms of blue light filters you are considering. Get a filter that eliminates all blue light up to about 500nm (for eye strain), 550nm (insomnia). And don’t fall for sales tricks like: “100% bad blue light blocking and no color distortion”, i.e. a clear looking filter. Remember that you can’t block blue light and see it too!

      Thanks again and best

      Like

      Reply

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