Hess Screen

Description

Hess Screen is used to test the function and co-ordination of the extra-ocular muscles to aid the diagnosis of ocular motility disorders.

The full set comprises a 92 cm x 92 cm size electronic grey screen with 25 red lights, a pack of corresponding recording charts, a green laser pointer with AAA batteries, red/ green dissociative goggles and a power unit.

Each item can also be purchased individually.

The fixation lights are positioned so that they are at 15-degree intervals when viewed at the correct testing distance of 50 cm from the screen. The red lights are illuminated one at a time, as selected by an operator holding the control unit. The screen markings also indicate 5 degree steps between the red lights. The fixation points are tangentially compensated in the way normal for any flat screen.

The patient should be seated so their eyes are directly in line with the central fixation point on the chart and instructed to move their eyes to view each red light as it is lit by the operator, then to indicate with the green laser pointer where that light appears on the chart. A chin rest is recommended to prevent head movement during testing.

The Hess Screen is designed to be wall mounted, usually in a room which can be darkened to a level suitable for both operator and subject. The screen unit is provided with two hanging plates. The power unit has a lead length of 1.5 metres and the control box lead is 3 metres from the chart.

Country of origin: GB