Special filters increase contrast in color vision deficiencies
Sustained use of broadband spectrally selective filters achieved an increase in chromatic contrast along with an adaptive response in observers with color vision deficiencies, according to a study published in Current Biology.
“About 6% of males and [less than] 1% of females have anomalies in their gene arrays coded on the X chromosome that result in significantly decreased spectral separation between their middle(M-) and long (L-) wave sensitive cone photoreceptors,” John S. Werner, PhD, University of California department of ophthalmology and vision science, and colleagues wrote. “Broadband spectrally selective filters [that are] proposed to improve the vision of color-deficient observers principally modify the illuminant and are largely ineffective in enhancing discrimination or perception because they do not sufficiently change the relative activity of M- and L-photoreceptors.”
Evaluating the long-term impact of spectral notch filters, 10 color vision deficient male participants wore either commercial notch filter Enchroma or placebo for 2 weeks. Participants kept a diary estimating daily use (mean, 7.7 hours/day; SD = 3.61) and were tested without wearing the glasses at day 2, day 4 and day 11.
Study results showed consistent increase in chromatic response from baseline across the patient population at day 11 (mean increase = 71%; 95% CI , 45- 96%). These findings demonstrate a positive L-M response over time as well as adaptation that carried over without filter use.
“We found that sustained use over 2 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,” Werner said in a press release from UC Davis Eye Center.
Further testing is required to determine how long improvement persists without filter wear, the researchers said in the journal article
“This is a neural effect that may lend itself to adaptation in visual therapies, not just for color vision, but perhaps for other visual modalities as well,” Werner and colleagues concluded.