Hi alamirah2,
Choosing the "right' sized implant is always a bit of an adventure. To start with, I urge you not to look at this as an exact science. Rather, you should have a general idea of the size you are looking for. Keep in mind that you yourself may have different desires at different times of your life, or perhaps even on different days of the week, for that matter. The difference between 650 cc's and 700 cc's is 50 cc's. That is approximately 2 ounces. Not a big difference. I don't think it is worth struggling to try to decide between these two sizes as there is a less than 10% difference between them.
To get a general idea of the look a patient is looking for, I find that using pre operative sizers is a great tool. I like to use Mentor's Volume Sizing System to help patients decide on a size. These sizers are tear drop shaped implants that patients put on prior to surgery in their bras to mimic the look they would like surgery to achieve.. At the same time, the surgeon is able to visualize this and thus give him or her a clear goal to create in the operating room. I, personally, find this method to be the most helpful as a communications means for implant sizes. I find them more helpful than looking at pictures or even using 3-D images. Unlike a 3-D image, Sizers are actually a three dimensional structure that the women can see as well as feel. She can wear them under particular clothing to give her both a visual as well as a tactile sense for that volume.
Good Luck,
Ary Krau MD FACS