Left or right?

I always wondered why various professions and technical fields have different names for left and right.  For instance, in optometry, OD (Oculus Dexter) and OS (Oculus Sinister) stands for right eye and left eye respectively.  Dexter and Sinister are the Latin words for right and left.  On a ship, the left and right side of the boat for someone on the ship facing the front of the ship are called port and starboard respectively.  My guess for the reason to introduce these terms is that when two people are facing each other and communicating it is not clear whose left and right sides are meant.  The following story told by my wife's aunt could also be another reason why such terms are used.  During a driver's test, the following exchange occurred:
Examiner: "Turn left at the intersection."
She: "Turn left, right?"
Examiner: "Right."
She turned right at the intersection and failed the test.

There are similar terms for other sides of an object as well.  For instance, the terms bow and stern are used to denote the front and back of a ship respectively and dorsum and ventrum denote the back and front sides of upright animals such as humans (or the upper and lower side of animals such as fish).