Near Maddox Rod Tests

The Maddox rod tests are selected by clicking on the H Phor or V Phor buttons on the Secondary Toolbar or by pressing 4 or 5 on the keyboard or remote control.

The Maddox Rod test is used for measuring the size of horizontal and vertical phorias. This test normally involves looking at a spotlight in a darkened room with the Maddox rod in front of one eye. The Maddox rod distorts the image of the spotlight into a thin streak. The images received by the two eyes are so different that the eyes will dissociate. The patient is asked if the streak passes through the spotlight. If it does not, prisms are used to centre the streak. The prismatic power required to achieve this provides a measure of the phoria.

To implement this test on a tablet screen it is necessary to use a bar instead of a spot in order to achieve adequate brightness. The colour of the bar can be changed from the Colours tab of the Program Options window.  Best results are obtained if the bar is matched in colour to the Maddox rod – i.e. a red bar for a red Maddox rod.

The bar on the screen should be oriented at 90 degrees to the axis of the Maddox rod – vertical bar for horizontal grooves and vice versa. The orientation of the bar is toggled by pressing any of the cursor control keys.

The patient views the screen from their normal reading distance and is asked to report if the streak seen with one eye passes through the bar on the screen. Prisms are used to centre the streak in the normal way.