These lines are located at parts where muscles running down from the jaw line to the chest wall are attached to the skin. They are naturally occurring and may be more obvious on some people.

You cannot "get rid" of visible necklines. However, as they are muscle attachments, you can use neuromuscular relaxant to weaken the muscles, thereby lightening their appearance.

Lasers or IPL will do nothing to these lines. Fillers are also not a good option for this area. Even the most carefully injected fillers will cast a shadow at certain lighting angles. Which means, you may just be exchanging one shadow (the lines) for another (the fillers).