Is it possible to switch to from round silicone to anatomical teardrop? (photos)

It is possible to switch, I however would first have this discussion with you Plastic Surgeon. Your photos are unfortunately not very helpful. A good physical examination will make a significant difference in determining what to do. Remember there are 30cc's in an ounce so the volume change you want may be more significant than you think. This would also adds weight that you are rightfully so concerned about, Good LuckStephen M. Davis, MD, FACSGreen Hills Plastic Surgery 

Teardrop implants are designed to look more natural by having more volume in the lower portion of the implant and less in the upper portion similar to a natural breast. The material that the implants are made out of are firmer than a silicone gel round implant in order to allow the shape to maintain even with gravity etc. There are different teardrop implants available and some have more projection than others. Going up in size will give you bigger breasts but switching to a teardrop from a round will take away some of the upper pole volume. A teardrop implant also required a bigger incision to place the implant than a round implant. It would be best for you to see a PS and undergo an exam to figure out what is the right choice for you to achieve your goals.