Optometry Practice

Christl Huber M.D.
Optometry · Natural Medicine

Reading - Print or Digital ? - A Guest Editorial about BLUE LIGHT

My Snowbird migrations, to a great extent, are driven by blue light. Sunny days during the Bavarian growing season surrounding a farm village and blue waters of the Gulf of Mexico along sandy beaches in Florida, the Sunshine State. Blue is the key word. My mate in these migrations, and in-house eye doctor, helped me understand the importance of the color blue.

But first an anecdote to my migrations: For most of the past two decades I supported my avid reading hobby by hauling bags of English language books in my luggage. The used books were mostly Florida thrift shop purchases. As I finished each book it went to a local thrift shop in Bavaria, which bundled them up for shipment to a Bolivian school in a charitable contribution to children. It seemed a silly waste to transport twenty-five-cent books twice across the ocean just to read them in my Bavarian nesting grounds. Even a charitable end did not compensate for the transport pollution and luggage hassle.

The solution was to take advantage of modern Internet technology. With my Florida library card, I can download free books to read on a smartphone while in Bavaria or anywhere. The added advantage is having a book always at hand for reading wherever I carry my phone — including bedside.

I started complaining about tearing eyes and eye strain shortly into this new reading approach swiping my way through more than ten-thousand “little” page from The Circle, Tribe, The Art of Wandering, The Accidental Billionaires, The Women in the Castle, The Other Einstein . . .. The diagnosis: my new hobby of constantly reading from a smartphone was due blue light fatigue.

It was explained to me that the human brain, which includes the eyes, evolved to see the world around us AND to control our circadian rhythm. This rhythm is part of a body clock that manages our sleep cycle. The eye receptors drive this clock. In the back of the eyeball is a layer called the retina, which contains light sensitive rods, color sensitive cones, and ipRGC (intrinsically photosensitive Retinal Ganglion Cells). About 120 million rods are the most light sensitive but lack color distinction. Another 6 million cones located in the central macula area are color sensitive in the “visible” spectrum distinguishing violet, blue, green, yellow, orange, and red. This spectrum is bordered by invisible ultra-violet and infra-red wavelengths on the electromagnetic radiation spectrum. The ipRGC receptors, also in the macula region, are excited by blue light and increase cognitive functions, in other words waking up in daylight hours (blue light) and inducing sleep in the dark (no blue light).

I am skipping over the complexities and mysteries of the ipRGC receptors in the retina that control pupil size and hormonal release of Melatonin from the brain to regulate sleep and wakefulness. It is sufficient to say that the blue light in our visible spectrum has a natural influence on our body rhythm or clock. Reading on a smartphone, tablet or any computer screen, especially at night, disrupts this natural rhythm.

Electronic gadgets all have screens made up of millions of pixels that simulate the sun or other forms of artificial lighting that rely on light emitting diodes (LEDs). The sun emits light that includes blue, which helps wake us up and keeps us wakeful until it sets. The blue light emitted by gadget screens are not controlled by the solar cycle and therefore can extend blue light emissions into unwanted hours.

Strides have been taken to soften the blue light of LEDs with fluorescent yellow coatings to create a white-screen background, but blue light directly emitted to the eyes is not totally eliminated. Another distinction is between light from screen and reflected light from a relatively rough paper surface of a book. The shorter wavelengths of reflected light (blue) are scattered by the roughness of the paper. Therefore paper book reading from reflected light of the sun or an artificial light source scatters much of the blue light before it enters the eye. However, blue light escaping the fluorescent coating of an LED manages to enter the eye and may confuse our circadian rhythm.

I’ll continue to read books from my smartphone for the free accessibility and convenience but will limit nighttime reading to paper books to not interfere with my circadian rhythm.

Footnote: For warmer colors on iPhone and Microsoft Windows:

On your iPhone or iPad: go to Settings > Display & Brightness. Tap the Night Shift setting, which alters the screen temperature of your device to a warmer color, filtering out the blue light.

On your computer with Microsoft Windows: Go to Settings > click on System, and, under Display, click to turn Night light on or off. You can also customize the color temperature or schedule by clicking “Night light settings.