Can the light outside the human visible spectrum damage our eyes?

Question

We’re often warned about how dangerous small commercial lasers can be for our eyes yet technologies like FaceID projects light in our faces many times a day.

Why is FaceID safe? Because it’s low enough power or because it’s in the non-visible spectrum?

Can the non-visible spectrum be dangerous for our eyes?

In: 40

Answer 1

(PhD in optics, have run ANSI safety calculations for medical implements)

There are two main ways for light to damage your retinas:

1. You can denature the proteins with high-energy wavelengths like ultraviolet light. That’s what happens when you stare at an eclipse.
2. You can burn them with ultraviolet (UV), visible, or infrared (IR) light. It’s mostly a problem with infrared because we don’t notice that the light is bright since we can’t see it.

In extreme cases you can damage them in other ways, like boiling the liquid and physically detaching the retina.

We mostly sustain damage from infrared (IR) and ultraviolet (UV) light because

1. We have a blink reflex that protects us from intense visible light. It’s very hard to get harmed by sunlight accidentally.
2. Very low frequency waves (like radio waves) don’t get absorbed by the retina, so there’s no transfer of energy.
3. While you can sustain damage from microwaves or e.g. gamma waves, we don’t run into them very often compared to UV and IR.

Lasers are especially dangerous because the your eyes are very good at focusing laser light down to a tiny pinpoint. All of that light energy gets concentrated in a tiny area, which then gets heated very quickly. IR lasers are more dangerous than visible because we don’t blink, but visible can still be dangerous if they’re high enough power.

EDIT: spelled out acronyms

Answer 2

(PhD in optics, have run ANSI safety calculations for medical implements)

There are two main ways for light to damage your retinas:

1. You can denature the proteins with high-energy wavelengths like ultraviolet light. That’s what happens when you stare at an eclipse.
2. You can burn them with ultraviolet (UV), visible, or infrared (IR) light. It’s mostly a problem with infrared because we don’t notice that the light is bright since we can’t see it.

In extreme cases you can damage them in other ways, like boiling the liquid and physically detaching the retina.

We mostly sustain damage from infrared (IR) and ultraviolet (UV) light because

1. We have a blink reflex that protects us from intense visible light. It’s very hard to get harmed by sunlight accidentally.
2. Very low frequency waves (like radio waves) don’t get absorbed by the retina, so there’s no transfer of energy.
3. While you can sustain damage from microwaves or e.g. gamma waves, we don’t run into them very often compared to UV and IR.

Lasers are especially dangerous because the your eyes are very good at focusing laser light down to a tiny pinpoint. All of that light energy gets concentrated in a tiny area, which then gets heated very quickly. IR lasers are more dangerous than visible because we don’t blink, but visible can still be dangerous if they’re high enough power.

EDIT: spelled out acronyms