A study has found that special patented glasses engineered with technically advanced spectral notch filters enhance colour vision for people with the most common types of red-green colour vision deficiency, known as anomalous trichromacy. Conducted by UC Davis Eye Centre, in collaboration with INSERM Stem Cell and Brain Research Institute, results also showed test subjects were able to identify and experience expanded colour when not wearing the glasses.
Worldwide, 350 million people suffer from red-green colour deficiency (CVD) and experience colours as more muted and washed out, or confusing and difficult to differentiate. People with normal colour vision see in excess of one million hues and shades whereas those with CVD see a much smaller range of colours.
The study evaluated the impact of spectral notch filters on enhancing the chromatic responses of observers with red-green CVD over two weeks of usage. The filters (EnChroma glasses) are designed to increase the separation between colour channels to help people with colour blindness see colours more vibrantly, clearly and distinctly.
I had no idea how colourful the world is and feel these glasses can help colour blind people better navigate colour and appreciate the world
During the study, participants wore the special filter glasses or placebo glasses, kept a diary and were re-tested on days two, four and 11 but without wearing the glasses. The researchers found that wearing the filter glasses increased responses to chromatic contrast response in individuals with red-green colour blindness. While evidence shows that the effects persist for some time after the removal of the glasses, it is unclear how long the improvement last.
“Extended usage of these glasses boosts chromatic response in those with anomalous trichromacy (red-green colour vision deficiency),” said John S. Werner, distinguished professor of ophthalmology and a leader in vision science at UC Davis Health. “We found that sustained use over two weeks not only led to increased chromatic contrast response, but, importantly, these improvements persisted when tested without the filters, thereby demonstrating an adaptive visual response.”
Mr Werner said the effect cannot be achieved with broad-band filters sold as aids to the colour blind. The findings suggest that modifications of photoreceptor signals activate a plastic post-receptoral substrate in the brain that could potentially be exploited for visual rehabilitation.
Alex Zbylut, a participant in the study, said “When I wear the glasses outside, all the colours are extremely vibrant and saturated, and I can look at trees and clearly tell that each tree has a slightly different shade of green compared to the rest.” Mr Zbylut first wore the placebo glasses and then tried the special filter version afterwards.
“I had no idea how colourful the world is and feel these glasses can help colour blind people better navigate colour and appreciate the world.”
John S. Werner, Brennan Marsh-Armstrong, Kenneth Knoblauch. Adaptive Changes in Color Vision from Long-Term Filter Usage in Anomalous but Not Normal Trichromacy. Current Biology, 2020; DOI: 10.1016/j.cub.2020.05.054