98th Annual Meeting DOG 2000

V 550

SLO – Funduscyclometry in natural viewing conditions

O. Ehrt, H. D. Schworm, K.-P. Boergen

Introduction: Measuring cyclopositon of the eyes with search coil or videooculography can only assess cycloduction and not the absolute cycloposition. Absolute measurements can be taken from fundus photographs or Scanning Laser Ophthalmoscope (SLO) images by analysing the position of the foveola and the optic disk. This can only be done when the patient is looking monocularly into the camera. Aim of the study was to develop a technique that allows natural viewing conditions during funduscyclometry.

Method: The scanning laser beam was deflected by 90° with a semitransparent mirror in front of the patient's eye. Thus the patient was able to look through the semitransparent mirror into the room, e.g. onto a Harms' screen. The SLO simultaneously images the central retina via the mirror through the undilated pupil. An image analysis program (Optimas 5.22) directly quantifies the cycloposition of the eye. Controlled head movements while fixing the centre of the Harms' screen allow measurements in different reproducible gaze positions under mon- or binocular conditions.

Results: The addition of the semitransparent mirror into the scanning beam reduces image brightness but image quality is sufficient for cyclometry after contrast enhancement. When imaging the retina with infrared laserlight the scanning beam can be vaguely perceived by the patient but does not interfere with natural viewing.

Discussion: Our modification of SLO-funduscyclometry allows direct measurements of absolute cycloposition in natural viewing conditions. This opens a new field for investigations of vertical and cyclodeviations and their sensory adaptations. The technique could be further simplified by using simultaneous binocular measurements, e.g. with the EAGLES device.

Department of Ophthalmology, Ludwig-Maximilians-Universität, Munich, Mathildenstr. 8, D – 80336 Munich, Germany