The Basics
Color vision is an important part of human visual perception, and it is possible due to the photoreceptors in the retina. The human eye consists of two basic photoreceptor cell types, rods, and cones. Rods are responsible for vision in dim light, and cones are responsible for bright light and enable perception of color. Individuals with normal color vision have three subtypes of cones with different wavelengths corresponding to their peak absorption. Found in the central part of the retina are the cones that are sensitive to either red light (long wavelengths ~555nm), green light (medium wavelengths ~530nm) and blue light (short wavelengths ~ 426nm). Normal color processing consists of the cones registering different colors and sending information through the optic nerve to the brain. This enables us to distinguish countless shades of color.
Color Vision Deficiencies
Color vision deficiency or known as color blindness could be congenital or acquired.
Congenital color deficiencies are typically bilateral and non-progressive, and acquired is
more likely unilateral and progressive. The types of color deficiency include red-green
deficiency and blue-yellow deficiency. Individuals with severe color vision defects lack
the photopigment to see color completely while others with a mild color vision defect
have a reduced sensitivity to certain colors. The degree of dysfunction varies between
individuals, mildly affected individuals may pass some of the less sensitive color vision
tests such as Farnsworth D-15 hue test. The most common type of color deficiency is red-
green deficiency. Color vision deficiency can be diagnosed through a comprehensive eye
examination. Testing that can be performed in clinic include, pseudoisochromatic tests,
arrangement tests (ex. Farnsworth D-15) and anomaloscope.
Treatment and Implications
Color vision deficiency can be frustrating and may limit participation in occupations that include being able to differentiate between colors. Few examples include pilots, truck drivers, law enforcement, and policing. There is no cure for inherited color deficiency. However, using specifically tinted eyeglasses or wearing red-tinted contact lens on one eye can increase some people’s ability to differentiate between colors.