A disease of the eye in which pressure within the eyeball damages the optic disc (8)

(Other definitions for glaucoma that I've seen before include "Eye condition causing weakening or loss of sight" , "Strange to say, a cola mug might cause an eye disease" , "A cola mug, strangely, might give you an eye disease" , "condition of eyeball affecting sight" , "A cola mug, strangely, could give you an eye disease" .)