An 8 x 8 table of numbers is displayed on the screen. The user is required to count how many times a certain digit (e.g. 5) occurs in the table. 

Any blurring or double vision that occurs while scanning the table will increase the time taken and/or lead to counting errors.

The test is carried out using black digits on a white background and optionally in the user's normal screen colours (the option to choose screen colours may be disabled from the System Administration). 

The accuracy of the count and the time taken are combined to give an index of performance.  A score of 50% or less indicates that performance was significantly below normal and may indicate a visual problem.  This result is then referenced against the other tests and information entered so as to gauge the significance poor performance