Brief intermittent light stimulation disrupts saccadic oculomotor control Tara L. Alvarez 1,2 , Kevin D. Beck 2,3 , Kenneth J. Ciuffreda 1,4 , Florence B. Chua 1,3 , Anuj Daftari 1 , Robert M. DeMarco 1,3 , Michael T. Bergen 1,3 and Richard J. Servatius 2,3 1 Department of Biomedical Engineering, New Jersey Institute of Technology, University Heights, Newark, NJ 07102, 2 Stress & Motivated Behavior Institute, University of Medicine and Dentistry of New Jersey, Newark, NJ, 3 NeuroBehavioral Research Laboratory, Veterans Affairs New Jersey Health Care System, East Orange, NJ, and 4 Department of Vision Sciences, State College of Optometry, SUNY State College of Optometry, New York, USA Abstract Purpose: This study sought to determine the effect of very brief, single and multiple pulses of light on spatial and temporal aspects of saccadic eye movements. Methods: Twelve visually normal, young adult subjects participated in the experiments. Horizontal eye position was monitored as subjects attempted to track target step displacements in the presence of either single or multiple brief flashes of light in the visual field. Results: Three primary findings were observed: (1) increased saccadic latency, (2) increased time for target acquisition and (3) increased initial saccadic error. Conclusion: The present findings suggest the influence of attentional processes and/or visual masking effects on saccadic eye movement control. Keywords: afterimages, distracters, oculomotor control, saccades, spatial attention, visual masking Introduction Brief and intense flashes of light may distract individuals from performing both ordinary and highly specific visual tasks (Yantis and Jonides, 1990; Theeuwes et al., 1999). For example, exposure to transient glare condi- tions while driving produces a significant reduction in the ability to detect pedestrians (Theeuwes et al., 2002). Furthermore, during night driving, glare from on- coming vehicle headlights decreases the visibility of low-contrast moving objects (Anderson and Holliday, 1995). Periodic laser glare has also been cited by the military to have adverse affects on the speed and accuracy of naval aviators locating visual information both inside and outside the cockpit (Reddix et al., 1992). Military personnel are also exposed to flashes of light in the battlefield. Additionally, flashes of light that elicit an afterimage can produce spatial disorientation in pilots, thus resulting in accidents and fatalities (Schmidt, 1999). It is unknown if such visual stimuli in the field may adversely affect oculomotor characteristics. Visual attention, visual afterimages, visual masking and/or neural inhibition may be potential sources of temporal and/or spatial changes in saccadic movements, in which the location of the flash or onset distracter may influence saccadic behaviour. Visual attention has been linked to the generation of saccades by many investiga- tors (Rizzolati, 1983; Krose and Julesz, 1989; Hender- son, 1992; Rizzolati et al., 1994; Kowler et al., 1995; Adler et al., 2002; Gersch et al., 2004; Peterson et al., 2004). This point has been refuted by Klein et al. (1992). A flash of light constitutes a distracting stimulus and may produce an inability to disengage attention, which may temporarily inhibit the generation of a saccade to the intended target. There are also numerous studies demonstrating that abrupt visual onsets can capture attention and create involuntary eye movement (Breitmeyer and Ganz, 1976; Jonides and Irwin, 1981; Received: 26 February 2007 Revised form: 13 November 2007, 29 January 2008, 18 March 2008 Accepted: 20 March 2008 Correspondence and reprint requests to: Tara L. Alvarez. Tel.: (973) 596-5272; Fax: (973) 596-5222. E-mail address: tara.l.alvarez@njit.edu Ophthal. Physiol. Opt. 2008 28: 354–364 ª 2008 The Authors. Journal compilation ª 2008 The College of Optometrists doi: 10.1111/j.1475-1313.2008.00569.x