Color-blind glasses are specially coated lenses that help people with color blindness to distinguish colors. Color blindness is caused by a genetic abnormality that leads to a defect in the development of the retinal cone cells that perceive vision, making it impossible for the patient to distinguish one or more colors. Take the most common red-green color blindness as an example, the patient wears a color-blind lens that filters green wavelengths of light in front of the right eye of the primary eye, and normal lenses in the left eye.