I note the previous comments with regard to slow practice and agree with them to some extent.  However, I think that there are times for slow practice and times for specific strategies to increase accuracy and flow in fast passages.  To practice a rapid passage very slowly may not be the best preparation for its execution in performance.  The reason for this is that in fast passages some finger percussion is necessary for clearly articulated sound and the rapid movement of the finger teaches the finger to land accurately.  A slightly slower tempo may help some aspects of performance such as intonation in ensemble performance but other practice methods may be more rapid and reliable in increasing accuracy and detail especially in fast passages – with less practice!  After all, once we have established a fluent performance it is so much fun to explore the musical aspects such as phrasing and dynamics.

What is being suggested here is that the rhythm or accent can be altered so that the ear is forced to listen to notes which otherwise may be glossed over.  For example:

1. If a study or other musical passage is written completely as quavers, then a dotted rhythm could be used, such as dotted quaver followed by semiquaver, or this rhythm can be reversed so that the short note is first. 
2. Another method is to stop after each group of notes.  In this method if the piece is in 4/4 then you could practice 4 quavers, stop, then play the next 4 quavers, stop and so on – as the playing improves the stops can be less frequent, say at the end of each bar.
3. Changing the natural accent of the bar is also an effective practice technique.  In this instance, instead of accenting the first of every 4 quavers, one could accent the second quaver of each group of 4 quavers for the entire piece or passage, or the third quaver, or even the fourth quaver.

These practice techniques help to refine the listening skills of the performer for greater accuracy, detail and fluency in performance and they may reduce the amount of practice time required – but they also make practice more interesting, developing bowing styles and freedom in playing – they are related to improvisation, yet another aspect of joy in playing an instrument!