Improve impoint sensitivity / easier marker selection with mouse

Hi, I'd like to know if there's any way of improving the sensitivity or "hit box" of an impoint in order to make it easier to select. I have a figure where I show an image and ask the user to place some markers (impoints), and then an ellipse is fit to those points and plotted in the same figure. The thing is, selecting the impoint markers is quite difficult.

Any tips would be appreciated!