Performing an examination

The patient sits 50 cm in front of the screen so that its mid-point is situated in his main direction of gaze, that is the primary position of gaze. The patient wears red and green goggles with the green lens in front of the left eye. To investigate the muscle functions of the left eye the ophthalmologist illuminates the fixed points in the main directions of gaze with a red laser light. This means that patient sees the red fixed points with the right eye through the red lens. He is asked to direct the light spot of the green laser pointer, which he guides himself using the hand he writes with, onto the red fixed point. When the fixation point changes the patient changes his direction of gaze and tries to target the fixed point again. The examiner marks the site of the green points on his examination chart. After all positions in the 9 main directions of gaze in the 15° field have been recorded graphically, the muscle functions of the right eye are tested in the same way. To do this only the laser pointers need changing. The ophthalmologist now marks the positions of the red light spot on the chart.

Small strabismic deviations are diagnosed more easily if the directions of gaze at a 30° distance from the main direction of gaze are tested as well as those at a 15° distance in the central measuring grid. Only in cases of more severe strabismus is testing in the 15° range sufficient. Measurement of cyclodeviations is not possible with this method.