Is Reading in the Dark Bad for Your Eyes?

Is Reading in the Dark Bad for Your Eyes? Videos

Is reading in the dark a bad idea?

Do you wonder if reading in the dark is bad for your kids eyesight? Do you or your child struggle with night vision?

While here is no strong scientific evidence suggesting that reading in the dark directly causes permanent eye damage or leads to conditions like myopia (nearsightedness) or astigmatism. There is the possibility that reading in the dark can cause eye strain or fatigue.
In this article we will cover more information on why some people have difficulty with night vision, called night myopia. Understanding if phone use at night is bad for the eyes. And share some tips to improve your night vision and reduce potential symptoms.

Why is my vision worse when I read in the dark? Night Myopia: What is it and is it bad for your eyes?

When we read in the dark, some people will experience poor or blurry vision, a phenomenon called night myopia. Studies have shown that young adults, particularly teenagers, are at a higher risk of having night myopia. But what causes this phenomena and is it bad for your eyes?

The prevailing theory was that night myopia happened because the person always had myopia (nearsighted), but because the demands on the visual system are more demanding at night, they only noticed poor vision at night time. In fact a simple google search will show lots of articles that state this as the definitive cause of night myopia.

However the true cause of night myopia is a little more complex. While the above may also be true, there is a lot more to night myopia than meets the eye (pun intended).

One theory is that our eyes change slightly in low light conditions, this small change leads to a blurring effect. (Salmon T. O. van de Pol C . (2006). Normal-eye Zernike coefficients and root-mean-square wavefront errors. Journal of Cataract and Refractive Surgery, 32:2064–2074. )

Another strong theory is that our eyes receive less information in low light conditions, and as a result, don't know where to focus. To compensate for the low light conditions, our eyes will focus closer than they need to, causing a bit of blur and strain. A 2012 study found that the defocus shift occurring in dim light is mainly due to accommodation errors and is generally present only in very low light conditions.(https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0040239)

There is limited research on the long term impact of night myopia, with no strong evidence that it has a long term harmful impact on vision. However since it is generally only present in extreme low light conditions, it is safest to try not to read in very low light conditions.

If you have difficulty driving at night or doing activities in the dark, it may indicate that there is more going on, and therefore it is always best to visit an optometrist for a comprehensive evaluation. Furthermore special lens coatings, adding light in the vehicle, and contrast training may improve your vision at night and reduce the risks of night myopia.

Take our online visual skills assessment to help identify if you or your child has a potential visual deficit that may be interfering with success in the classroom, work, or sports.

Can using a phone, tablet, or computer at night harm your vision?

When it comes to using a digital screen at night there are many different aspects consider.

Is the type of light from a screen harmful?
Is there a scientific consensus on what harm is caused by blue light?
Is there enough light from a screen to cause harm?
Does night mode (a setting on most devices that reduces blue wavelength of light in the screen) void the harm of digital screen use at night?
Do blue light blocking glasses reduce any risks of blue light from digital screens at night?

Is the type of light from a screen harmful?

Light is made up of a variety of colors across the spectrum, certain wavelengths are potentially more harmful to your eyes, these are in the blue spectrum of color. Specifically high-energy visible light (HEV light) is short-wave light in the violet/blue band from 400 to 450 nm in the visible spectrum is considered more dangerous to the eye.

There are concerns that this light can harm the retina over extended periods, and that it can impact the circadian rhythm cycle which regulates melatonin production and sleep.

Is there a scientific consensus on what harm is caused by blue light?

No, there is a lot of uncertainty in the scientific community regarding the harm of blue light to the retina and to our sleep cycle. There are many studies that contradict each other or a limited in scope and are hard to apply as a general rule. Furthermore there are no studies that look at the long term impact of blue light on children.

A fantastic article by Dr. Professor Rosenfield from SUNY College of Optometry explains why blue light from screens is less of an issue than you might think
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Is there enough light from a screen to cause harm?

If blue light causes strain, then sunlight would be the real problem. The sun emits 100,000 lux, 25% in the blue spectrum. So 25,000 lux exposure. Laptop computers: 1.7 to 14.5 lux. Tablets: 0.7 to 5.9 lux. Smartphones: 0.6 to 2.1 lux. TVs: 0.03 to 0.5 lux. Indoor lighting 50-200 lux. With 6%-40% blue light.
So 1 minute of sunlight is equivalent to....12,000 minutes in front a cell phone. (not to mention that most cell phones/computers/tablets have the ability to reduce or entirely block out blue light in night mode). Therefore the studies that relate to the impact of blue light on our eyes from digital devices would only be relevant if they are examining extremely low levels of blue light over time.

Do blue light blocking glasses reduce any risks of blue light from digital screens at night?

Assuming that there are risks associated with blue light from digital screens, there is still a question whether blue blocking glasses actually benefit. The reason being is that to entirely block blue light, the glasses would drastically reduce the image quality that a person sees, as well as having a strange tint to them. Therefore most blue blocking glasses only reduce a small percentage of blue light transmission to begin with. Take for example one of the popular brands, Hoya’s Blue Control which reduces the 436 nm wavelength by 4%, 480 nm by 3% and 490 nm by 3%
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So wearing Hoya Blue Control for indoor use (assuming 200 lux (super high) and 40% blue light (super high). Would filter out 4% of blue light, or 3.2 lux of blue light. Whereas reducing sunlight which is 25,000 lux of blue light exposure, would equate to thousands of times more important than the glasses.

This article in review of optometry titled "Living With Blue Light Exposure: The sun is your biggest enemy, and digital devices aren’t as bad as you think" provides a very comprehensive understanding of this point.

Is Reading a Kindle Better for Your Eyes Than Reading a Book?

One common question that people have is whether reading from a kindle is better for your eyes than reading from a book. The truth is that it doesn't really matter what you're reading, as long as you're doing it in good lighting conditions.

If you're reading from a kindle, make sure that the contrast between the letters and the background is significant enough to prevent strain. You don't need to have the brightness cranked up to the maximum, but you should be able to read comfortably without squinting.

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Night Reading in Good Lighting Conditions: Tips for Better Eye Health and vision

The good news is that you can take steps to improve vision for night-time reading and protect your eyes while reading in the dark.

Follow these tips to ensure that you're giving your eyes the proper conditions for healthy and functional vision:

Change contrast on digital devices: If reading on a computer or phone, change contrast settings to use white letters on a dark background. Recent studies demonstrated that the incidence of night myopia can be greatly reduced based on the configuration of visual stimulus. (https://jov.arvojournals.org/article.aspx?articleid=2191990)

Use bright lighting: When reading, it's important to have good lighting that illuminates the page. A good rule of thumb is to make sure the light source is behind you and shining on the page at an angle. This will prevent any glare and ensure that the page is well-lit.

Avoid too much glare: While bright lighting is essential, too much glare can also be harmful to your eyes. If you're reading from a computer screen or tablet, consider using an anti-glare screen protector. This will reduce the amount of glare that reaches your eyes and prevent strain. If you are driving at night use anti reflective coatings on your lenses.

Choose the right contrast: Whether you're reading from a physical book or an e-reader, it's important to have good contrast between the letters and the background. This will make it easier for your eyes to read without having to strain.

Drive with a light on in the car: Some people who have difficulty driving at night may find that adding light inside the car will improve their vision.

Consider using colored tints or filtered lenses: Different colored lenses can be helpful at reducing glare and improving contrast for those who have difficulty at night. Specifically NoIR Yellow #58 and NoIR Yellow #465 are considered beneficial for night driving.

Consider visual training to improve contrast sensitivity: If you experience difficulty driving, reading, or seeing at night, contrast training has been shown to significantly improve visual outcomes. Learn about our multi-center study on RevitalVision for contrast training.

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