Do colour blind glasses work? What the research actually shows

Colour blind glasses change how colours look. They do not give you normal colour vision. Both halves of that sentence matter, and most of the frustration around these products comes from the gap between the marketing and the second half.

If you want the short answer: some people with red-green colour deficiency find them genuinely useful outdoors, the effect is a change in colour discrimination rather than a correction, and they will not let you pass a colour vision test.

What colour blindness actually is

Normal colour vision uses three types of cone cell in the retina, each most sensitive to a different band of wavelengths — roughly short, medium and long. Your brain compares their outputs to derive colour.

The common forms of colour blindness are not missing cones. In protanomaly and deuteranomaly — which together account for most red-green colour deficiency — the long- or medium-wavelength cone is present but its peak sensitivity is shifted, so the two responses overlap much more than they should. The brain gets less difference to work with, and reds and greens become hard to separate.

Less commonly, a cone type is genuinely absent (protanopia, deuteranopia) or there is only one cone type working (monochromacy).

That distinction is the whole basis for why filters can do anything at all.

What the filters do

The lenses used in these products are notch filters: they remove a band of wavelengths in the region where the two overlapping cone responses are most similar.

The effect, for someone with anomalous trichromacy, is to increase the difference between what the two cones report. Less overlap means more signal difference, which the brain can read as a larger colour difference.

The cost is that you are removing light, and with it information. Some colours become less distinguishable even as reds and greens become more so. Overall brightness drops, and the whole scene shifts in a way that takes getting used to.

For someone with a cone genuinely absent, there is much less to work with. Filtering cannot create a comparison between two signals when there is only one.

What the research shows

This is where honesty matters, because the marketing and the literature do not say the same thing.

Measurable changes in colour discrimination tasks: yes. Multiple studies have found that these filters alter performance on colour arrangement and discrimination tests, and that subjects can detect colour differences they could not detect unaided.

Restored normal colour vision: no. Studies that have looked for this have not found it. The filters change the pattern of colour confusion rather than eliminating it, and performance on standard clinical colour vision tests does not normalise.

Subjective benefit: mixed and genuinely individual. Some users report a strong and welcome effect — colours described as more vivid, foliage separating from flowers, traffic lights becoming clearly distinct. Others report little or nothing, or find the overall shift unpleasant.

The honest summary from the clinical literature is that these are aids that change colour appearance, with real effects for some individuals, and that the strong claims some manufacturers make are not supported.

What they will not do

They will not let you pass an Ishihara test. Studies have specifically examined this, and the filters do not reliably convert a failing result to a passing one. Some make performance worse.

They will not satisfy an occupational colour vision requirement. Pilots, some rail and maritime roles, certain electrical and military positions have colour vision standards, and these are tested without filters for good reason — the filter does not give you the discrimination the role requires, it redistributes it. Attempting a test with them is also generally prohibited.

They will not work for total colour blindness. Achromatopsia is a different condition, and filters do not address it. People with achromatopsia usually have significant light sensitivity instead, and for them tinted lenses help with that rather than with colour — the approach in sunglasses for light sensitivity is the relevant one.

They do not change permanently. Take them off and your colour vision is what it was.

Who tends to find them worth it

From reported experience and the pattern in the studies:

People with moderate anomalous trichromacy — a shifted cone rather than an absent one — see the largest effects.

Outdoors, in bright natural light, where there is plenty of light to spare and the scene is full of reds and greens. Landscapes, gardens, autumn foliage are where people describe the strongest impression.

For specific tasks rather than all-day wear: picking ripe fruit, sorting coloured wiring, reading a colour-coded chart, distinguishing plant health.

Where they help least: indoors under artificial light, in dim conditions, and for tasks needing fine discrimination of colours outside the red-green axis.

The practical questions to ask before buying

Is there a return policy? The individual variation is large enough that this is the single most important question. Buy from somewhere that will take them back.

Do they state the actual tint and transmission? A notch filter is a specification. A listing that only says "colour enhancing" is not describing anything.

Do they block UV? This is separate and non-negotiable if you are wearing them outdoors. A tinted lens with no UV filter dilates your pupil and admits ultraviolet, which is worse than no lenses — see UV protection vs dark lenses.

Are they polarized, and do you want that? Unrelated to colour, useful outdoors, with the exclusions in who should not wear polarized sunglasses.

What do they cost? The market ranges from inexpensive to several hundred dollars, and price does not track effect.

A cheaper thing to try first

Before spending on specialist lenses, it is worth knowing that an ordinary brown or amber lens does a mild version of the same thing.

Brown tints attenuate short wavelengths and lift contrast, and some people with red-green deficiency find that red and green separate slightly better through a good brown lens. It is a much smaller effect than a purpose-built notch filter, and it costs a fraction as much. Our lens colour guide covers what brown does generally.

Not a substitute for the real thing if the real thing works for you — but a cheap experiment that tells you whether filtering does anything for your particular colour vision.

What actually helps day to day

Worth saying, because eyewear is only one approach.

Colour identification apps on a phone will name the colour of anything the camera sees, which solves the practical problems — which wire, which resistor, is this ripe — more reliably than any lens.

Labelling and ordering systems at home and at work.

Asking. Unglamorous and effective.

A formal diagnosis if you have never had one. Knowing which type you have tells you whether filters are likely to do anything, and an optometrist can test it properly in minutes.

Getting tested properly first

Before spending anything, knowing which form of colour vision deficiency you have tells you whether filters are likely to do anything at all — and the test takes minutes.

Anomalous trichromacy — a shifted cone — is where filters have the best chance, because there are two overlapping signals for a filter to separate.

Dichromacy — a missing cone type — leaves much less to work with.

Achromatopsia is a different condition entirely, usually with significant light sensitivity, and filters do not address colour at all.

An optometrist can distinguish these, and knowing the answer turns a gamble into an informed decision. Online colour vision tests are unreliable because screen calibration varies.

What to expect in the first hour

If you do try a pair, the initial impression is misleading in both directions.

The immediate effect is dramatic and often emotional, because every colour shifts at once. That is the shift, not the benefit.

The real question is after a few days: can you now distinguish things you could not before, in the situations that matter to you? Some people find a genuine lasting benefit; others find the novelty fades into a tint they do not enjoy.

Which is why a return policy matters more than the price.

Frequently asked questions

The short version

They change colour appearance; they do not correct colour vision. The effect is real for some people with red-green deficiency and absent for others, and the difference is which form you have.

They will not pass a colour vision test, and they are not a route around an occupational standard.

Buy only with a return policy, check the UV specification separately, and try a good brown lens first as a cheap experiment. And if you have never been formally tested, start there.