I came across an interesting study from Sendtec and Eye Tools where they looked at the correlation between the visibility of an area on a search result page and the click through rates. The results where not that surprising though; the areas and links seen by more people also received more clicks. The correlation was very strongly positive (.95) between visibility and clicks. This study supports the argument that if an area on a web page or a link etc is not seen it will probably not be clicked. Eye tracking can thus help you predict which areas will be clicked and help you improve click through rates by making important links and areas more visible.
Read more about the study here: http://www.sendtec.com/EyeTools-GoogleCheckOut-Addendum.aspx