Is It Bad to Wear Sunglasses All the Time?

Short answer: Wearing UV400 sunglasses outdoors is not bad — on the contrary, they protect your eyes from UV radiation. Problems arise from wearing them in low light or indoors, which can affect how your eyes adapt to light and even your sleep.

If you regularly wear sunglasses in dark environments, everything from your sleep schedule to your eyes' ability to adjust to changes in light could be put at risk.
That said, most of us should probably wear sunglasses more often, especially outdoors, when we need to protect our eyes from harmful ultraviolet (UV) rays.

Let's look at how sunglasses protect our eyes and why wearing them all the time can actually cause vision and sleep problems.

Can constantly wearing sunglasses harm our eyes?

Generally no, when the sunglasses are good quality and have certified UV protection (UV400). In that case, wearing them helps comfort and protects against UV radiation. Quality, certified sunglasses reduce discomfort from bright light, improve visual comfort and protect the eyes from UVA/UVB radiation.
Caution: the risk arises when glasses have no UV protection, because a dark lens can dilate the pupil and let more harmful radiation into the eye.

Wearing sunglasses indoors does not damage your vision, but it can tire your eyes and cause fatigue. That in turn can lead to headaches, blurred vision and increased sensitivity to light. This is especially true of cheap sunglasses, whose poor optical quality can add to eye strain.

On top of that, wearing sunglasses too often keeps your pupils dilated for long periods. This exposes your whole visual system to less light and can reduce your retina's ability to adjust quickly to brighter conditions.

People with photophobia, or excessive sensitivity to light, may find some relief wearing sunglasses indoors, but eye doctors discourage it. Wearing dark-lensed sunglasses indoors can worsen photophobia over time, and can even trigger the condition in people who had no light-sensitivity issues before.

How do sunglasses work?

When properly certified, the lenses filter ultraviolet radiation (UVA/UVB), reduce light intensity and improve visual comfort in bright sunlight. UV400 lenses block ultraviolet radiation up to 400nm.

Your eyes are exposed to less light when you look through a pair of dark sunglasses. Normally, when the ambient light is dim, our pupils dilate automatically to let more light reach the retina. This involuntary reflex lets us adapt to changing light and see in near-darkness as well as bright sunshine. It is controlled by the autonomic nervous system, so it happens without our thinking about it.

Wearing sunglasses triggers the same reflex, especially indoors, where your brain perceives the surroundings as unusually dark. Many of the effects of overusing sunglasses come from keeping the eyes dilated for unusually long periods.

Can wearing sunglasses constantly affect sleep?

Usually not, if you wear them when you should. But if you wear sunglasses in low light or indoors, you reduce the exposure to natural light that helps regulate your circadian rhythm.

Our sleep-wake cycles are governed by hormones released daily in response to changing conditions around us. Light-sensitive photoreceptors in our retinas play a vital role in controlling circadian rhythms — the physical, mental and behavioural changes that follow a daily cycle. Light is the main regulator of our day-to-night cycle and influences everything from metabolism to sleep. That means we need exposure to bright light during the day, especially in the morning, to regulate the quality of our sleep.

Wearing sunglasses all day blocks exposure to morning light and can disrupt your body's normal sleep rhythms — it is like staying in a dimly lit room all the time. Wait until after 9 or 10 a.m. to put them on if you want to protect your ability to sleep well.

Which sunglasses are best for everyday wear?

For everyday use, look for glasses clearly marked UV400 (or an equivalent 100% UV certification), a good fit with coverage around the eye, and quality lenses free of optical distortion. Polarized lenses additionally reduce glare and are especially useful for driving and at the beach.

Caution: avoid sunglasses without UV protection

It is especially important not to wear sunglasses with inadequate UV protection too often, particularly outdoors. Glasses that lack the necessary UV-blocking lenses will cause your pupils to dilate, which increases the amount of harmful solar radiation your eyes are exposed to and raises the risk of eye conditions such as cataracts, retinal tissue damage and macular degeneration.

When buying sunglasses, always look for a clear label stating UV400 or 100% protection. You can also ask an eye doctor to check any sunglasses you already own to make sure their UV protection is adequate.

Conclusion

Wearing sunglasses often outdoors is generally safe — as long as they are certified, since UV protection is the single most important feature. What you should avoid is uncertified glasses and wearing them in low light or indoors.

Note: This article is informational. For personalised vision advice, consult an optician or eye doctor.