Following a range of recent design changes, Google is currently rolling out a new layout/interface for its image results. Previously, if you clicked on an image from a list of their image results, you would be taken off to the site where the image was found. However, with this new interface you stay on Google’s results page while being shown the original image (usually larger than the thumbnail that Google provide on their results page). See below for an example:
You can see from the image above, that instead of taking you through to the source once the image has been clicked, Google instead provides you with the option to either visit the page that the image is found on, view the original image or view the image details (size, etc.).
There are many reports from webmasters that visits from Google image results are down due to the above changes, and they are understandably aggrieved. A main positive of the change however, is reduction in the time it takes to see a larger version of the image when clicked (as you no longer need to visit and load the webpage that the image was found on).
You can read Google’s thoughts behind this recent change at http://googlewebmastercentral.blogspot.co.uk/2013/01/faster-image-search.html