The raw data coming from the eye tracker will in many cases be converted to fixations and saccades. The algorithms used for this do vary quite a bit in the results they will produce, and all of them are also very sensitive to parameter settings. It is highly recommended to double check the results against the raw data (BeGaze has a tool for this) to verify that the conversion is correct, or at least as expected. Direct comparisons between different studies are impossible for this reason, at least as far as fixation data is concerned.