“The world is a carousel of color” are lyrics to the theme song for the television show, Walt Disney’s “Wonderful World of Color” that premiered in 1961. Suddenly, black and white television wouldn’t do. People wanted to see that wonderful world in their living rooms! We now take that carousel for granted, but color vision perception is an amazing and complex process involving the eye and the brain, and now, that perception can be enhanced.
To understand color vision enhancement, we first need to understand the color vision perception process. Our brain processes and translates electrochemical signals generated by the retina into visual perception. Essentially, the eye provides, and the brain decides. When visible light strikes photoreceptor cells in the retina, it initiates the visual cycle, converting the light into electrochemical signals. The initial color signals produced are the result of three color-sensitive cone photoreceptors that absorb the light according to their unique peak wavelength sensitivities. Next, the retinal ganglion cells refine the electrochemical signals, and these signals are transported from the retina to the brain via the optic nerve. Ultimately, the light signals reach the visual cortex of the brain’s occipital lobe.
Color signals are the product of cone photoreceptor cells in the retina, where the combined response of the unique pigment opsins of the (S)short-blue, (M)medium-green or (L) long-wavelength red cone receptors are responsible for the many hues (colors) that the brain perceives. Color perception is the collective response of the three absorption spectra of the S, M and L cones combined with the neuronal interactions between the retina and the rest of the brain. We see with our brain, and the retina is an extension of our brain. The range of discernable colors is defined by the response of the three types of cone photoreceptors. Despite having only three color receptors, however, some experts have theorized that our eyes see over 10 million different colors. Think of the three color cartridges in a printer that produce full color images, then how much more our eyes can do!
How can color vision perception be made better? Spectral colors can be correlated with wavelength, but the same color can be the result of a combined response from multiple wavelengths. Blocking the transmission of specific wavelengths in the overlapped areas eliminates color confusion and allows the brain to process a more precise signal for clearer color perception and enhanced contrast. Our eyes have general difficulty with blue light, both in focusing and from its increased tendency to scatter. Both the defocus and the resulting haze reduce color and contrast sensitivity. Color vision enhancement generally begins with some attenuation of the blue-violet region ranging from 400 nm to 500 nm. A properly designed notch or band filter that suppresses specific wavelengths in the overlapped area, can help better separate the signals passed to the brain. A tailored spectral control filter can improve chromatic contrast and enhance the experience of color.
Lens products that manipulate light signals and products that manipulate wavelengths of light to enhance color vision are now available. An optical material called a notch filter, which can block the exact wavelengths of light in the location where they overlap, results in a simplified differentiation of colors. The lenses block specific wavelengths to create a clearer separation of different color signals so that they can be better interpreted by the brain. Band-pass filters block all wavelengths except those belonging to a specific spectral range (the so called pass-band) and therefore filter out unwanted ambient light that negatively affects the visual contrast needed for color discrimination.
The human eye is unable to see the entire visible light spectrum clearly because it has difficulty distinguishing light at the boundaries where pure color peak wavelength responses merge or overlap and produce color confusion at the blue with green and green with red junctures. Filtering out the confusing light at these boundaries helps increase clarity and color definition with vibrant contrast and vivid detail. New color enhancing lenses selectively block blue wavelengths of light and attenuate specific yellow wavelengths to produce a visual experience with more vivid colors, better depth perception, enhanced clarity and high definition. These lenses can help everyone enjoy a more vivid carousel of color.