What are colorblind glasses?

Colorblind glasses use tinted lenses to help some people with color blindness see colors better. They're usually made for people with certain forms of red-green color blindness (the most common type).

Unfortunately, there's no cure for color blindness right now. These special glasses can't give a colorblind person normal color vision, but they could help some colors look more vibrant or noticeable.

How colorblind glasses work

There are photoreceptor cells along the back of your eye (retina) called rods and cones. The cone cells react to colored light from the outside world and help people see in color.

An eye with normal color vision has three kinds of cones. One type detects red colors, one detects green and one blue.

Color blindness happens when:

• Some (or all) of the cones are there, but they don't work very well.

• Some (or all) of the cones are missing.

The medical term for color blindness is color vision deficiency. Most people who have the condition are born with it, but some diseases and medications can cause it too.

Almost all colorblind people can still see some colors. Total color blindness is very rare.

Red-green color deficiency is by far the most common type of color blindness.

There are four different kinds of red-green deficiency. They are:

• Deuteranomaly – Some greens look more red. Most people with red-green color vision deficiency have this type.

• Protanomaly – Some reds look more green and faded.

• Protanopia – It's hard to tell the difference between green and red due to missing red cones.

• Deuteranopia – It's hard to tell the difference between green and red due to missing green cones.

There's a good chance you or someone you know is at least a little color blind. About 1 in 12 males and 1 in 200 females are born red-green color blind.

There are other types of color blindness too, but they're rare. They include:

• Blue-yellow color deficiency – There are two different types. Tritanomaly makes blue and green look similar, as well as yellow and red. Tritanopia makes blue look similar to green, purple similar to red and yellow similar to pink.

• Blue cone monochromacy – Only the blue cone cells work, but most colors look grayish. This is the rarest type.

• Achromatopsia – None of the cones work well or at all. It can make all colors look much less vibrant (incomplete achromatopsia) or remove all colors completely (complete achromatopsia).

Colorblind glasses work by blocking certain colors so you can see other colors better. This can help people tell certain colors apart or even see a new color.

For example, someone with deuteranomaly has weaker green cones. Shades of green look more like red.

This happens because red and green overlap on the visual spectrum. That's where this person's stronger red cones "win" because they send better signals to the brain.

They would choose glasses that let through more green and less red, specifically targeting that overlapping part of the spectrum. That way, green and red won't have to compete as much, and the brain receives a clearer signal.

These glasses usually work best for people with mild color blindness. And they can only help colorblind people who have all three types of cone cells.

They won't help people who are missing one or more of the cones altogether because there aren't any color signals to "strengthen."