OD/OS
OD means right eye. oculus dextrus.
OS means left eye. oculus sinister.
These are holdover terms from cool latin times! We still use them. Conventionally, OD always comes before OS. Optometrists use this convention as standard.
But why do you use them??? Just use right eye left eye??? Why do you have to make everything complicated????
If you have to write out 'right eye and left eye' every single time, that can become tedious especially when you're talking to cool vision improvement people who know what they're talking about.
'OD/OS' is five characters. 'right eye, left eye' is nineteen characters. Use the longer version if you insist :P