Fan and block test

The Fan and Block test is displayed by selecting the Fan icon on the Primary toolbar, pressing F5 on the keyboard or selecting Fan on the remote control handset.

The Fan and Block test is used to determine the axis and magnitude of astigmatism.  The fan is used to determine the presence of any astigmatism and its principal axes.

The blocks are used in conjunction with cylindrical lenses to neutalise the astigmatism.

Pressing the vertical cursor control keys repeatedly swaps between the Fan and the Blocks mode.  Alternatively, each mode may be selected by selecting the corresponding icon on the Secondary toolbar or by pressing 1 or 2 on the keyboard or the remote control.

Changing the angle

The angle of the arrow on the fan or the blocks can be changed using the vertical scrollbar on the Floating Control Window of by pressing the horizontal cursor control keys on the keyboard or remote.

Step size

By default, the angle is changed in 5 degree steps.  Pressing Shift and and the horizontal cursor control keys on the keyboard causes the angle to change in 1 degree steps.  The angle can also be changed in 1 degree steps using the vertical scrollbar on the Floating Control Window.

Revealing the current angle

In Fan mode, the current angle can be read directly from the chart.  If the Floating Control Window is used, the angle is also displayed in the Test Information Bar as shown below:

Alternatively, selecting the R icon on the Secondary Toolbar or pressing R on the keyboard or remote will display a small window on the test chart showing the current angle.

Summary