Are the position of the images randomized, or you show always the non-intervention version on the same side?
It's a little too long. I'll try to complete it later.
The images take too long to load, and you can see how they are constructed. It is slightly weird.
The order of the images is completely randomized - so the survey is never the same for two participants. The images however follow a complex algorithm - no image pair shows up twice. The number of images - although admittedly quite high - is the absolute minimum amount to simulate every important condition/decision-combination relevant for surgery. The load time was optimized - however depending on your location and server load it might of course be a little to long (I try to further improve that). Thank you very much for your support!
Perhaps you can download all the parts in hidden images and combine them on demand. Also, perhaps you can render the images in a hidden canvas while the user is selecting the previous pair of images, so when the user makes a click the change has no pause.