Which of the following is NOT true regarding X-chrom contact lenses?

The correct understanding of X-chrom contact lenses centers on their purpose and functionality. These contact lenses are specially designed for individuals with color vision deficiencies, particularly red-green color blindness. One of the key attributes of X-chrom lenses is that they shift cone photoabsorption towards longer wavelengths by filtering light and enhancing contrast, particularly for colors that may be difficult to distinguish.

These lenses are indeed tinted red, which is another aspect of their design to assist with color discrimination. They can help individuals with color deficiencies to perceive colors more vividly, thus aiding in color discrimination tasks.

Acting as neutral density filters, however, is not true regarding X-chrom contact lenses. Neutral density filters are used primarily for reducing the intensity of all wavelengths of light equally, without altering color balance or perception. X-chrom lenses specifically modify the wavelengths of light that reach the retina, thereby influencing color perception rather than simply reducing overall light intensity. This focus on enhanced color discrimination and specific wavelength manipulation distinguishes X-chrom lenses from neutral density filters.