Eye movements in surgery: A literature review

With recent advances in eye tracking technology, it is now possible to track surgeons’ eye movements while engaged in a surgical task or when surgical residents practice their surgical skills. Several studies have compared eye movements of surgical experts and novices, developed techniques to assess surgical skill on the basis of eye movements, and examined the role of eye movements in surgical training. We here provide an overview of these studies with a focus on the methodological aspects. We conclude that the different studies of eye movements in surgery suggest that the recording of eye movements may be beneficial both for skill assessment and training purposes, although more research will be needed in this field

Mechanisms of Action and Targets of Nitric Oxide in the Oculomotor System

Nitric oxide (NO) production by neurons in the prepositus hypoglossi (PH) nucleus is necessary for the normal performance of eye movements in alert animals. In this study, the mechanism(s) of action of NO in the oculomotor system has been investigated. Spontaneous and vestibularly induced eye movements were recorded in alert cats before and after microinjections in the PH nucleus of drugs affecting the NO–cGMP pathway. The cellular sources and targets of NO were also studied by immunohistochemical detection of neuronal NO synthase (NOS) and NO-sensitive guanylyl cyclase, respectively. Injections of NOS inhibitors produced alterations of eye velocity, but not of eye position, for both spontaneous and vestibularly induced eye movements, suggesting that NO produced by PH neurons is involved in the processing of velocity signals but not in the eye position generation. The effect of neuronal NO is probably exerted on a rich cGMP-producing neuropil dorsal to the nitrergic somas in the PH nucleus. On the other hand, local injections of NO donors or 8-Br-cGMP produced alterations of eye velocity during both spontaneous eye movements and vestibulo-ocular reflex (VOR), as well as changes in eye position generation exclusively during spontaneous eye movements. The target of this additional effect of exogenous NO is probably a well defined group of NO-sensitive cGMP-producing neurons located between the PH and the medial vestibular nuclei. These cells could be involved in the generation of eye position signals during spontaneous eye movements but not during the VOR.Fondo de Investigación Sanitaria Grants 94/0388 and 97/2054Comunidad Autónoma de Madrid Grant 08.5/0019/1997Dirección General de Investigación Científica y Technológica Grant PB 93–117

The effect of eye movements on traumatic memories and the susceptibility to misinformation : a partial replication : a thesis presented in partial fulfilment of the requirements for the degree of Master of Arts in Psychology at Massey University, Manawatū, New Zealand

The issue of whether certain techniques used in psychotherapy might increase false memories is a major source of contention between cognitive and practising psychologists. Recently, a study by Houben, Otgaar, Merckelbach, and Roelofs (2018) found that bilateral eye movements used in Eye Movement Desensitisation and Reprocessing (EMDR) therapy increase susceptibility to misleading information. EMDR is a popular treatment for posttraumatic stress disorder and is primarily thought to reduce the vividness and emotional intensity of traumatic memories. Individuals who undergo EMDR therapy may be more susceptible to misinformation that is inadvertently introduced by the therapist due to reductions in memory vividness. Despite strong theoretical links between eye movements and false memories, few studies have investigated this effect. The current study addressed this issue by attempting to replicate the study by Houben et al. (2018). This study also investigated the working memory account underlying EMDR by comparing eye movements to an alternative dual-task. An initial pilot study comprising a reaction time task established that attentional breathing taxed working memory most comparably to bilateral eye movements. The main study predicted that eye movements would increase susceptibility to misinformation and that eye movements and attentional breathing would lead to comparable reductions in memory vividness and emotionality. 94 students (Mage= 25.74, SDage= 9.68) were recruited to participate in the study at Massey University, Manawatū, New Zealand. Participants viewed a five-minute video depicting a serious car accident. Afterwards, they were randomly assigned to perform either eye movements, attentional breathing, or a control task while simultaneously recalling the car accident. Participants rated the vividness and emotionality of their memory before and after performing the tasks. All participants then received misinformation about the video before completing a recognition test. Results indicated that the misinformation effect was not replicated, with no effect of eye movements on susceptibility to false memories. Findings also suggested that eye movements and attentional breathing were ineffective in reducing the vividness and emotional intensity of the trauma memory. The present study raises questions about the validity of materials and procedures used to instil the misinformation effect. Limitations of the study and key areas for improvement are considered for further investigation

Miniature Eye Movements Enhance Fine Spatial Details

Our eyes are constantly in motion. Even during visual fixation, small eye movements continually jitter the location of gaze. It is known that visual percepts tend to fade when retinal image motion is eliminated in the laboratory. However, it has long been debated whether, during natural viewing, fixational eye movements have functions in addition to preventing the visual scene from fading. In this study, we analysed the influence in humans of fixational eye movements on the discrimination of gratings masked by noise that has a power spectrum similar to that of natural images. Using a new method of retinal image stabilization18, we selectively eliminated the motion of the retinal image that normally occurs during the intersaccadic intervals of visual fixation. Here we show that fixational eye movements improve discrimination of high spatial frequency stimuli, but not of low spatial frequency stimuli. This improvement originates from the temporal modulations introduced by fixational eye movements in the visual input to the retina, which emphasize the high spatial frequency harmonics of the stimulus. In a natural visual world dominated by low spatial frequencies, fixational eye movements appear to constitute an effective sampling strategy by which the visual system enhances the processing of spatial detail.National Institutes of Health; National Science Foundatio

A Relative Position Code for Saccades in Dorsal Premotor Cortex

Spatial computations underlying the coordination of the hand and eye present formidable geometric challenges. One way for the nervous system to simplify these computations is to directly encode the relative position of the hand and the center of gaze. Neurons in the dorsal premotor cortex (PMd), which is critical for the guidance of arm-reaching movements, encode the relative position of the hand, gaze, and goal of reaching movements. This suggests that PMd can coordinate reaching movements with eye movements. Here, we examine saccade-related signals in PMd to determine whether they also point to a role for PMd in coordinating visual–motor behavior. We first compared the activity of a population of PMd neurons with a population of parietal reach region (PRR) neurons. During center-out reaching and saccade tasks, PMd neurons responded more strongly before saccades than PRR neurons, and PMd contained a larger proportion of exclusively saccade-tuned cells than PRR. During a saccade relative position-coding task, PMd neurons encoded saccade targets in a relative position code that depended on the relative position of gaze, the hand, and the goal of a saccadic eye movement. This relative position code for saccades is similar to the way that PMd neurons encode reach targets. We propose that eye movement and eye position signals in PMd do not drive eye movements, but rather provide spatial information that links the control of eye and arm movements to support coordinated visual–motor behavior

Recent Saccadic Eye Movement Research Uncovers Patterns of Cognitive Dysfunction in Schizophrenia.

The frontal cortex and the subcortical areas of the brain play a major role in the control of thought and action. Eye movements are increasingly used in neuropsychological research to explore the executive and sensorimotor functions of such neural networks. This interface links the control of action, at the fundamental levels of neurophysiological and neurochemical processes, with the high-level cognitive operations that underlie visual orienting. Patients with schizophrenia have neurocognitive impairments that can be readily investigated with novel saccadic eye movement paradigms. Animal, human lesion, and neuroimaging studies have identified the cerebral centers that underlie saccadic eye movements. The areas of the prefrontal cortex include the dorsolateral prefrontal cortex, the frontal eye fields, the supplementary eye fields, and the anterior cingulate gyrus. Pathology of saccadic eye movements therefore provides information on the functional status of the underlying neural circuitry in brain disorders such as schizophrenia

Measuring miniature eye movements by means of a SQUID magnetometer

A new technique to measure small eye movements is reported. The precise recording of human eye movements is necessary for research on visual fatigue induced by visual display units.1 So far all methods used have disadvantages: especially those which are sensitive or are rather painful.2,3 Our method is based on a transformation of mechanical vibrations into magnetic flux variations. In order to do this a small magnet is embedded in a close-fitting soft contact lens. The magnetic flux variations caused by eyeball movements during fixation are measured by means of a SQUID magnetometer. The recordings show the typical fixation pattern of a human eye. This pattern is composed of three kinds of movements: saccades, drift and microtremor. The last-mentioned type of movements are displacements in the order of 2 μm. It is possible to distinguish between movements which are perpendicular to each other

Exploration of the functional consequences of fixational eye movements in the absence of a fovea.

A recent theory posits that ocular drifts of fixational eye movements serve to reformat the visual input of natural images, so that the power of the input image is equalized across a range of spatial frequencies. This "spectral whitening" effect is postulated to improve the processing of high-spatial-frequency information and requires normal fixational eye movements. Given that people with macular disease exhibit abnormal fixational eye movements, do they also exhibit spectral whitening? To answer this question, we computed the power spectral density of movies of natural images translated in space and time according to the fixational eye movements (thus simulating the retinal input) of a group of observers with long-standing bilateral macular disease. Just as for people with normal vision, the power of the retinal input at low spatial frequencies was lower than that based on the 1/f2 relationship, demonstrating spectral whitening. However, the amount of whitening was much less for observers with macular disease when compared with age-matched controls with normal vision. A mediation analysis showed that the eccentricity of the preferred retinal locus adopted by these observers and the characteristics of ocular drifts are important factors limiting the amount of whitening. Finally, we did not find a normal aging effect on spectral whitening. Although these findings alone cannot form a causal link between macular disease and spectral properties of eye movements, they suggest novel potential means of modifying the characteristics of fixational eye movements, which may in turn improve functional vision for people with macular disease