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  • Published on:
    The educational value of Saccades
    • Damian T Roland, Consultant and Honorary Associate Professor Leicester Hospitals and University
    • Other Contributors:
      • Ben McNaughten, Paediatrician

    Many thanks for your response to the editorial ‘What are you looking at?’, which highlights some important principles for this extensively studied research area (despite being a relatively new field in healthcare) [1]
    Despite the emergence of new methods to analyse gaze behaviour terminology has not been revised to reflect scientific advances. A recent article by Hessels et al. outlined significant inconsistencies in the definitions of fixations and saccades held by eye movement researchers and highlighted the conceptual confusion surrounding these terms.[2]

    The term saccade is derived from the French for ‘jerk’. The phrase appears to have been coined by Emile Javal, a French ophthalmologist, in the 1800’s.[3] By 1916 it had been accepted into the English literature.[4]

    Saccades are frequently defined in the literature as rapid, ballistic movements of the eyes that abruptly change the point of fixation.5 Definitions have included;

    ‘Rapid eye movements used to voluntarily move gaze from one target of interest to another.’[6]

    ‘Ballistic movements, 20-150ms long, reaching a velocity up to 800°/s. They direct the eye so that external visual objects are projected onto the fovea.’[7]

    ‘Rapid eye movements used in repositioning the fovea to a new location in the visual environment.’[8]

    The term ballistic refers to the fact that the saccade-generating system cannot respond to subsequent changes in the position of a target during th...

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    Conflict of Interest:
    None declared.
  • Published on:
    The educational value of Saccades

    Dear Sir,

    As a final year medical student, I read with great interest this article highlighting the pedagogical value of gaze study. Whilst the article raises many poignant features of this new medium of data collection, I believe the definition of saccade in your article may be slightly incomplete.

    The article states that “Saccades...are movements of the eyes between fixations in which information is not meaningfully acquired or absorbed.” However, I would suggest that whilst the primary purpose of saccades may be to move between fixation points, there is subconscious information acquisition completed by these movements-- the subconscious identification of a lack of pathology.

    If one does not take certain regions of an image as fixation points, it suggests that they are not looking for pathology in those regions. This is reinforced by one study analysing gaze study in mammogram analysis which reported that “long saccades often missed the target but were followed by corrective saccades”. (1-Kundel H, Nodine C, Conant E et al. Holistic component of image perception in mammogram interpretation: gaze-tracking study. Radiology 2007;242(2):396-402.) This highlights that within a saccade is also inert analysis of a lack of pathology rather than just transformational eye movement.
    Another study analysing a gaze study of virtual histopathology slides between trained pathologists, residents and medical students reported that “fully trained pathologists h...

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    Conflict of Interest:
    None declared.