The inability to perceive, or to see, colors: The doctor told Sam that his achromatic vision was a result of a severe congenital deficiency in color perception which might be associated with nystagmus (the involuntary rapid rhythmic movements of his eyeballs) and reduced visual acuity (loss of the ability to detect fine details or small distances with the eyes).

The doctor also indicated that he has several other patients with similar abnormal achromatic visions.