Tuesday, October 9, 2012

What does OD and OS mean?

I am looking to buy a pair of coloured contact lenses for Halloween. But I don't understand what this OD and OS thing means, when I go to buy them. What does it mean and how do I know what number to choose?
Added (1). I don't wear glasses or contact lenses, normally. I have perfect vision.
Added (2). These lenses don't need prescriptions. They are for costumes and if you just want different coloured eyes. I just need to know how to figure out what number to choose, since I don't need help seeing.It's just for the colour.
Added (3). Http://www.honeycolor.com/geo-ultra-black-ck105.html
These are the ones I'm looking to get, but I don't know what OD or OS number to pick. Can someone tell me what is best for someone who doesn't need help with sight.It's just for the colour change.
>>> What does OD and OS mean?