Reducing blue light exposure to the eye may potentially minimize its harmful effects, but a new study in Clinical and Experimental Optometry suggests blue-blocking lenses can cause unintentional consequences, including a reduction in color contrast sensitivity, particularly at low light levels.

A team of Australian researchers enrolled five healthy participants (one man and four women) who were between 23 and 39 years old. The study used three blue-blocking lenses and a clear lens without a blue-filtering coating.

The researchers analyzed the different lenses in two different scenarios. In experiment one, they measured color contrast thresholds using a visual search color detection task in which the color (red, green, blue and yellow) of the target circle stimulus was systematically reduced using a staircase procedure. In experiment two, the researchers quantified color contrast thresholds for a range of short wavelengths near the attenuation transmittance range of the lenses.

In both experiments, color contrast was impaired only in blue colors and was most evident at low contrasts. Additionally, the blue-blocking lenses with lower transmittance profiles showed greater reductions in color contrast sensitivity, which affected color contrast thresholds.

“Optometrists need to be mindful of this when prescribing the appropriate blue-blocking lenses for individuals who work in environments in which blue light is prevalent,” researchers wrote in their paper.