Put another way, suppose you have trouble seeing objects at a distance and you can only see out to 20 ft what a person with normal vision can see out to 200 feet, then you have 20/200 vision. The 6/6 terminology is more commonly used in Europe and Australia, and represents the distance in metres.
1 SID, also s.i.d., is a veterinary abbreviation meaning to give medication once a day. 2  Medical professionals for humans instead use the term qd (an abbreviation for quaque die). 3  However, that term can be easily mistaken with the term qid (an abbreviation for quarter in die), which means four times a day.
L. quaque die, every day. Most experts in the prevention of health care errors recommend that the abbreviation q.d. be written out as âdailyâ in order to prevent communication errors. q.d may be confused with q.i.d (four times a day), a mistake that could result in an unintentional overdose.