Abstract
Purpose: :
A slow periodic oscillation of the eye position occurring during visual fixation has been identified. To our knowledge, this type of eye movement has not been described before. The aim was to describe its characteristics.
Methods: :
Eye movements were recorded binocularly in six healthy subjects. In test 1 the effect of three different recording techniques was analyzed: infrared corneal reflection technique with head mounted goggles (XY1000, IOTA Inc.); head mounted video oculography (VOG; Chronos Vision); and Scleral Search Coil (SSC: Skalar Inc.). In test 2 the effect of sampling frequency was evaluated by using the SSC with different sampling frequencies (120, 140, 160, 180 and 200 Hz). The eye position data was band-pass filtered (0.05-0.15) and the oscillatory components of the eye position were evaluated by a fast fourier transformation (FFT).
Results: :
A consistent finding in all test subjects and recordings was a slow periodic oscillation of eye position i.e. the eye position oscillated (amplitude ±0.5 deg) in a horizontal-vertical elliptical track. The duration of a complete oscillation was approximately 10 seconds. The FFT analysis thus revealed an prominent peak value (~0.1 Hz) with large intra-individual variation but small inter-individual variation, independent of recording technique, sampling frequency or related to blinking.
Keywords: eye movements • eye movements: recording techniques