Text Size: a  |   a 

Color Blindness Could Be Early Sign of MS

September 7, 2017

Visual symptoms, such as flashes of light or eye pain, are common in multiple sclerosis and are caused by inflammation of the optic nerve (a condition called “optic neuritis”. However, one symptom that’s often overlooked is an impairment of color vision. These impairments take the form of problems seeing certain colors or difficulties distinguishing between different colors.

Different wavelengths of light are detected by specialized cells in the retina of the eye. Rod cells detect low light and have little in involvement in color vision. The three types of cone cells found in humans are most sensitive to three wavelengths of light that roughly correspond with three colors: long wavelength (red), medium (green) and short (blue). Another way of describing it is that we see colors in an opposing way: either red or green (hence traffic lights); either blue or yellow; and either black or white. When cones are stimulated by light, the retina and optic nerve process this information into a color and relay this to the brain. The ability to see colors varies from species to species (dogs have difficulty distinguishing orange from red), and from person to person. My blue may be your mauve.

People with hereditary color blindness typically have a genetic defect in their ability to produce the proteins needed to detect color. This gene is found on the X chromosome, so color blindness is more common in men (who have only one copy of the X chromosome) than in women (who have two copies of X). Color blindness affects about 8% of men and less than 1% of women of European descent.

However, the impaired color vision in MS isn’t true color-blindness and isn’t related to a genetic defect. Rather, it’s caused by the same inflammatory process that causes MRI lesions in the brain. What’s affected is the optic nerve. This nerve lies outside of the central nervous system, but is actually an extension of the CNS (rather than being a peripheral nerve). This means that optic nerve is the most accessible part of the CNS available for scrutiny, and provides some indication of what’s going on in the brain. MS inflammation causes damage to the optic nerve, just as lesions in the CNS cause damage to nerve fibers in the CNS.

READ MORE via MSology