The vision or fixation span is the length of a word or words a reader can take in or recognize within one fixation. This is a fixed span usually enough to take in a word at a time.

Reading research indicates that the human's fixation span is around five printed letters long for each fixation. A reader can see a five letter word, but will not be able to understand a following word of five letters at the same time.

Beyond the fixation span, an experienced reader can use some cues to help them to read and a reader may recognise the length of words so that they can automatically judge the best place for the next fixation.

It has been suggested, primarily through popular psychology that the fixation span can be stretched through training meta guiding to take in as much as a line for the purpose of skimming or speed reading. This suggestion has found to be false, which goes some way to explain why skimming results in a severely reduced comprehension rate in comparison to normal reading (rauding).