I've posted a few studies that have looked at how people's eyes move across comic pages (here and here), and I recently found another. This short study looked at when people's eye movements skip panels or go back and re-read them.
They found that people spend more time reading panels with text than with just images, and that panels without text are more likely to be skipped and to be read with peripheral vision. Unusual panel arrangements (i.e. non-horizontal then vertical arrangements) also possibly led to jumping over panels (as was found in another study as well). After skipping these panels, participants then backtrack and re-read them.
These findings are consistent with previous studies that compared the eye-movements of expert and non-expert comic readers. Non-experts tend to focus more on text and read more erratically throughout a page. Experts tend to read more smoothly and focus more on the images.
General studies like this are interesting, though I'd really like to see more studies that specifically target specific issues. Are there particular features of page layouts that motivate skipping panels? Are there features of layouts that impede on the actual comprehension of panels? Once we get beyond these very basic sorts of "what do eyes do generally" studies, we can really start exploring how looking at eye-movements can tell us about the comprehension of comic pages.