Can you wear blue light glasses with contact lenses?

Can you wear non-prescription glasses over contact lenses?

Yes. The contact lens corrects your vision, the glasses do something else. LOWLIGHT is sold without a prescription and worn instead of ordinary glasses, so someone with lenses in sees just as sharply with the glasses on as without. Nothing in the lens affects the contact lens or the other way round, and every LOWLIGHT model fits over contact lenses the way a pair of sunglasses does. The question worth asking is a different one: if the contact lens already filters blue light, do you need the glasses at all?

Doesn't the contact lens already filter blue light?

Usually not. When a contact lens is sold with UV protection, it refers to light outside the visible spectrum. Class 1, the strictest class, means the lens lets through less than 10 per cent of UVA and less than 1 per cent of UVB. Visible blue light, which screens and LED lamps emit most of, sits higher up the spectrum and passes an ordinary clear lens almost unhindered. A clear lens is supposed to be clear.

The blue band is also the one that matters for the evening. Brainard and colleagues shone single wavelengths between 420 and 600 nm at 72 participants and found that light between 446 and 477 nm suppressed melatonin most (Journal of Neuroscience 2001). That is the part of the light the eye's clock cell responds to. More on the mechanism in Blue light and melatonin.

Are there contact lenses with a blue light filter?

Yes, a few. The best known is a photochromic lens the US FDA cleared in April 2018. It darkens in bright sunlight and returns to a faint tint indoors. According to the manufacturer it blocks up to 15 per cent of blue light indoors and up to 55 per cent outdoors, calculated under the ISO 8980-3 standard for 380 to 460 nm. The FDA noted at the same time that the lens is not a substitute for sunglasses, because it does not cover the whole eye.

Researchers have also tested a prototype lens that filters roughly 60 per cent of short-wave light between 380 and 450 nm (Renzi-Hammond et al. 2022, Eye & Contact Lens). It was a prototype, and it was measured for glare, not for evening light.

Can you compare the percentages directly?

Not entirely. The contact lens figure is weighted by a retinal hazard curve and covers 380 to 460 nm. Our figures are the lens's filtration within its band, unweighted, from the supplier's spectral measurement per colour. Two percentages with different bands and different methods do not say the same thing, and that goes for every brand. How to read such a figure, and the three questions that expose one that was never measured, is in What the percentage on blue light glasses means.

What can be said is the difference in order of magnitude. A contact lens meant to be worn all day, in traffic and in daylight, cannot be orange. So it stays at a faint tint indoors. A pair of glasses you put on after sunset has no such constraint, and can therefore filter almost everything in the blue band.

What happens in the evening when the lenses come out?

This is where the question turns practical. In a Swedish survey of 562 contact lens fittings in 2017, 83 per cent were for full-time wear, and among soft lenses 58 per cent were monthly lenses and 37 per cent daily disposables (Johansson, Morgan and Gierow 2019). Most people have their lenses in from morning to evening, and many take them out at some point before bed.

LOWLIGHT has no prescription. Someone who sees blurry without lenses and takes them out at nine therefore has two options: keep the lenses in for the last screen hours, within the wearing time the optician has given, or switch to their ordinary glasses. With the lenses kept in, it is glasses on on the sofa and lenses out when the screen goes off. If you see well enough without lenses to read your phone, you can wear LOWLIGHT on its own.

What else happens to your eyes at the screen when you wear lenses?

You blink less. A review in Acta Ophthalmologica in 2022 reports measurements where blink rate fell from 26 times a minute in conversation to 14.5 times a minute at the screen. That applies to everyone, with or without lenses. A pair of glasses does not change how often you blink, and we make no claim about dry eyes. Dryness with lenses is a question for your optician.

What does the evening look like with lenses and LOWLIGHT?

• At the desk during the day: LOWLIGHT ONE with the amber lens, 75–80 % between 415–455 nm, over your lenses for long screen sessions.
• After sunset: Orange · Evening on the sofa, in front of the TV and the phone. It filters 98 % of blue light.
• The last hour before bed: Red · Night, 99 % between 400–550 nm, if you are still reading or playing.
• Lenses out when the screen goes off, or earlier if your optician says so.
• Late gaming: the same lens as the evening, see Blue light glasses for gaming.

It is not a treatment and we measure no effect on sleep or eyes. What we can say is what the lens lets through, and that it sits just as well over contact lenses as without.