Eye Health

Do Colour Blindness Glasses Work? What the Evidence Shows

The viral videos are real, and so is the disappointment for many buyers. Here is what these lenses actually do, who they can help, and who they cannot.

🕔 8 min read👁 Eye health📚 Research

What colour blindness actually is

The retina contains three types of cone cell, each most sensitive to a different range of wavelengths, broadly long, medium and short. Colour perception comes from the brain comparing the signals from all three.

In the most common forms of colour vision deficiency, one cone type has its sensitivity shifted so that it overlaps heavily with another. The cones are present and working. Their responses are simply too similar to be told apart cleanly, so certain colours become difficult to distinguish.

This is why the term colour blindness is misleading. Very few people see no colour at all. The overwhelming majority see colour, but with reduced ability to separate particular pairs, most often reds from greens.

What the lenses do

These lenses use notch filters. Rather than dimming light evenly, they remove a narrow band of wavelengths at the point where two cone types overlap most heavily.

By cutting out the region where the two responses are most similar, the filter increases the difference between the signals the two cone types send. The brain receives a larger contrast between them and reports colours as more distinct.

The result, for some wearers, is a genuine and sometimes striking increase in the vividness of certain colours, particularly reds and greens against natural backgrounds.

Enhancement is not correction

This distinction is the whole story, and it is the thing marketing tends to blur.

That third row matters most for anyone with a practical reason to need colour vision. Studies examining performance on standard clinical colour vision tests have generally not found that these filters produce reliable improvement in scores. The wearer's experience of colour changes. Their measured ability to identify colours correctly largely does not.

Who they help and who they do not

The people most likely to benefit have mild to moderate red-green deficiency of the type where cone sensitivities overlap rather than being absent. For them the filter has something to work with.

People with a completely missing cone type generally see little benefit, because there is no overlapping signal to separate. The filter removes light without creating any new distinction.

People with blue-yellow deficiency, which is rarer, are less well served by filters designed around the red-green overlap.

There is also a practical limitation that gets little attention. The filter removes light, so these lenses are dark and work best in bright outdoor conditions. Indoors and in low light the effect diminishes considerably, and the reduced brightness becomes a cost rather than a benefit.

How to think about it before buying

First, get your specific type and severity established properly. The benefit depends heavily on which cone is affected and how much, and self-diagnosis from an online test is not a sound basis.

Second, set expectations against the right claim. If the appeal is a richer experience of landscapes and flowers in bright daylight, many wearers are satisfied. If the expectation is being able to reliably name colours, or resolve a practical problem at work, the evidence does not support it.

Third, be sceptical of any product promising to cure or correct colour blindness. Colour vision deficiency is genetic and structural. A filter changes the light entering the eye while it is worn. It does not change the retina.

Whatever the outcome on colour, the lens should still do the basic job of a lens. Ultraviolet protection is not optional simply because a filter has an additional purpose.

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