The blind subject was studied similarly. He refused formal ophthalmological examination, but had been told many years previously that he suffered from congenital glaucoma. He lost all subjective light perception at age 40, but was otherwise in good health and active in volunteer activities involving services for the visually impaired. The patient was unable to detect the fixation lights or the background panel even at its brightest setting of 2500 lux. Prior to the experiment his hand was passively located 300 upward and 30° downward. On verbal commands, 'up' and 'down' he was asked to direct his eyes to the imagined hand locations. ' There was no visible impairment in his ability to move his eyes in any plane.