High Quality Content by WIKIPEDIA articles! The King-Devick Test (K-D Test) is defined by Mosby’s Medical Dictionary as a tool for evaluation of saccade, consisting of a series of charts of numbers. The charts become progressively more difficult to read in a flowing manner because of increasing space between the numbers. Both errors in reading and speed of reading are included in deriving a score. Saccades are quick, simultaneous movements of both eyes.