How to Do a Blue Light Glasses Test (Daytime & Nighttime Lenses)

There’s a lot of hype around blue light-blocking glasses and a million brands to choose from, but how can you tell if your glasses are actually blocking blue light? Thankfully, there are a number of tests you can do at home to judge the quality of your lenses. We’ve put together a helpful list of ways to determine if your glasses are really blocking blue light, whether they’re clear computer glasses for daytime or darker yellow or orange lenses or nighttime. We'll also share expert advice about choosing blue light-blocking glasses from board-certified ophthalmologist Kara Hartl, MD, F.A.C.S. If you’re ready to kick blue light to the curb, read on!

How to Test Blue Light Glasses

An illustration of an RGB chart showing overlapping red, green, and blue circles.

Board-certified ophthalmologist Kara Hartl, MD, F.A.C.S., says clear blue light-blocking lenses for daytime use are a little yellow. Test yours by looking at something light blue or white through them. If your lenses are dark yellow or orange, look at something dark blue. If it looks black, the lenses block blue light.

Section 1 of 6:

How to Tell If Daytime Glasses Block Blue Light

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Check the color of the light reflecting off your clear lenses. The light bouncing off your lenses shows which colors are being blocked. Hold your lenses up to a light source and check the colors reflecting off them. If you see the color blue, you know your glasses are blocking at least some blue light.^{[1]
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- This is the simplest test you can do at home, but it doesn't indicate how much blue light is being blocked (ideally, you want to block 30% of blue light).
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Kara Hartl, MD, F.A.C.S., is a board-certified ophthalmologist and a blue light expert. She specializes in studying the effects of natural and artificial light on people's eyes and bodies.
The blue of the sky should look yellowish through your clear lenses. Dr. Hartl says blue light-blocking clear lenses have a slight yellow tint that isn’t super noticeable when you’re wearing your glasses on your face.^{[2]
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Kara Hartl, MD, FACS
Board Certified Ophthalmologist

Expert Interview} To check if they’re tinted, go outside and hold your glasses up toward the blue sky on a clear, bright day. If the sky looks warmer or yellow through the lenses, then they’re blocking at least some blue light.

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Look at a white background through your clear lenses. White should look yellowish if the lenses are blocking blue light. All you need for this test are your glasses and a white background (a computer screen or sheet of paper will work just fine). Hold your glasses up to the background and look through the lenses to check for a yellow tint.^{[3]
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- The color warms up because there are special pigments in the lenses designed to absorb blue light passing through.
- If the lens is clear and the color of the background doesn’t warm up, it means there is only a basic anti-reflective coating that filters about 5 to 20% of blue light maximum.

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How to Tell If Nighttime Glasses Block Blue Light

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Compare orange lenses to a screen’s "night mode" setting. "Night mode" should look like your view through orange lenses. Many devices have a "night mode" that blocks blue light from their display. First, look without your glasses at a phone or computer with night mode on. Then, turn off night mode and look at the screen with your glasses on. Depending on how intense the night mode setting is, the images should look pretty similarly warm or yellow-orange in color.^{[4]
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- On Apple devices, this setting is called Night Shift. On Android, it’s called Eye Comfort Shield.
- Night mode settings essentially do the same work as blue light-blocking glasses, but not all devices have the software to do this.
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Do the Black and Blue Square Test. Through dark orange or red lenses, the color blue should look black. Darker nighttime lenses block most (if not all) blue light. Look up "black and blue square test" online to pull up an image of a black square next to a blue square. Put on your glasses and see how the blue square changes to test your lenses.^{[5]
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- If your lenses are filtering out blue light, the blue square should now look black or dark gray.
- If the blue square still looks blue, your lenses are not blocking enough blue light.
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Look at an RGB color chart. Orange or red lenses should darken the blue portion of a color chart. "RGB" stands for "red, green, blue" and this chart will show you all the colors humans can see. Look up "RGB color chart" or "RGB color wheel" online and look at the chart through your glasses to check their blue light-blocking ability.^{[6]
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- The blue portion of the chart or wheel should turn gray or black if your lenses are blocking blue light. The green portion should also darken.
- The darker the green portion, the better (especially for orange or red lenses designed for nighttime use).

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How to Ask for a Spectrum Report

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A spectrum report shows the full range of light blocked by your lenses. If the manufacturer is reputable, they won’t hesitate to send you a report (it’s a red flag if they insist you just take their word). For clear computer glasses, check to make sure the lenses filter out at least 30% of blue light before you buy a pair.^{[7]
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- Yellow evening or driving lenses should block about 65%-70% of blue light.
- Orange and red nighttime lenses designed for sleep should block 95%-100% of blue light.
- If a manufacturer won’t provide a report or you’re suspicious of the accuracy, take your glasses to your eye doctor or an independent company with a lab-grade spectrometer. They’ll be able to tell you how much blue light is being blocked and at what frequencies.^{[8]
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What blue light test should you avoid?

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Avoid the blue light pen test, since its results aren't accurate. Some companies provide a "blue light pen" (a small flashlight that shines blue light) you can shine through the lenses of their glasses as proof that they block blue light. However, these pens often emit violet light (which is right next to blue on the light spectrum), not blue. This marketing technique is widely regarded as a scam.^{[9]
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Section 5 of 6:

Benefits of Blue Light Blocking Glasses

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Wearing blue light glasses can help you sleep better at night. Blue light wavelengths help set your circadian rhythm (your sense of when it's time to go to bed), but too much blue light at night can disrupt that rhythm. If you're having trouble sleeping but can't avoid looking at screens, wearing blue light-blocking glasses at night might help you relax.^{[10]
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- Blue light glasses don't reduce eye strain. The best way to reduce eye strain from looking at screens all day is to take frequent breaks. Follow the 20-20-20 rule: every 20 minutes, look at an object 20 ft (6.1 m) away from you for 20 minutes.
EXPERT TIP

Kara Hartl, MD, FACS
Board Certified Ophthalmologist
Dr. Kara Hartl is a board certified Ophthalmologist and the Founder and CEO of Mountain View Eye Center in Fairbanks, Alaska. Dr. Hartl is a blue light expert and specializes in studying the effects of natural and artificial light on people’s eyes and bodies. She received a BA in Biology from Harvard University and earned her Doctor of Medicine (MD) from The University of California-San Diego Medical School. Dr. Hartl also trained at the world-renowned Bascom Palmer Eye Institute. She is passionate about incorporating technology into the future of eye care and has started a public education initiative to inform everyday LED screen users about the effects and the easy ways to protect themselves while continuing to use their devices. Dr. Hartl also founded the international non-profit, Gift of Sight, which is dedicated to curing blindness across the globe.

Kara Hartl, MD, FACS
Board Certified Ophthalmologist

Wear yellow lenses to support your sleep cycle. If your glasses aren't yellow, they're not doing much to protect your sleep. Use them only during the evening hours before bed when the blue light from LED screens can alter your circadian rhythm and damage your sleep quality.

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Where to Buy Blue Light Blocking Glasses

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Buy blue light glasses at a grocery store or pharmacy. If you don't need prescription lenses, you can buy blue light-blocking glasses from just about anywhere! Look for them in the eye care section of your grocery store or pharmacy. They might also be on the same display as the reading glasses.
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Order prescription blue light glasses from your optometrist or online. You can usually ask your optometrist's office to add a blue light filter to your prescription lenses. If you order your glasses online from a website like Zenni or Zeelool, you can usually opt for a blue light-blocking filter as you're customizing your lenses.
- Cost for non-prescription lenses: $10+
- Cost added to prescription lenses: $17-$300

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What if my lens is reflecting violet light and green?

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They are most likely ultraviolet (UV) Glasses, which block ultraviolet light.

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Does regular glass block 100% of blue light?

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No, regular glass does not block 100% of blue light. Standard glass blocks some UV and a small portion of blue light, but much of it still passes through. To filter blue light more effectively, you would need specially coated lenses or blue light–blocking glasses.

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