Adaptive Images not working for certain wordpress media?

Adaptive Images not working for certain wordpress media?

I've recently followed the instructions at http://adaptive-images.com/ to
get my website to automatically scale for various screen sizes.
I am, however, using a (now very modified) wordpress theme that includes a
javascript image slider and portfolio page. Although I have learned a lot
of coding since first installing this wordpress theme, I do like the
slider and Portfolio page and want to keep them.
My question is, adaptive images works well when the media is simply
inserted as an img tag in the body of my post. however, my index.php and
other files call for 'slides' and 'portfolio thumbnails' which have
hardcoded sizes in functions.php via add_image_size
e.g.
add_image_size( 'grid-thumb', 180, 230, true );.
For these types of images retrieved, there is really no way adaptive
images loads a smaller version of them. However, their container, such as
the image slider, still changes in width to accomadate the screen.
How do I work this out? Thanks in advance for everyone on this forum that
makes the web so much better for a beginner.