Nonconjugate adaptation of human saccades to anisometropic spectacles: Meridian-specificity

Abstract Recently it has been demonstrated that saccades become different in size in the two eyes if a subject is adapted to anisometropic spectacles, which provide visual images of different magnitude to the two eyes. These nonconjugate adaptations adequately meet the requirements of those spectacles and, once acquired, they persist (with some reduction) even during monocular viewing. We now demonstrate that such nonconjugate adaptations of saccades can be meridian-specific, if there is a pressure for such meridian-specificity. This pressure was provided by means of a cylindrical spectacle-lens. Adaptations along a vertical, horizontal or oblique meridian did not transfer to the orthogonal meridian. These results demonstrate a capability of saccadic adaptation to deal with calibration problems restricted not only to one eye, but even to one specific plane of muscular action. Our results also suggest that the meridian-specific adaptations of oblique saccades take place at a stage before the decomposition of motor commands into separate horizontal and vertical components. The meridian-specific nonconjugacies were also expressed in smooth-pursuit eye movements. Post-saccadic drift adapted only along the horizontal meridian

The relationship between standard automated perimetry and GDx VCC measurements

PURPOSE: To investigate the relationship between retinal light sensitivity measured with standard automated perimetr

Asymmetrical adaptation of human saccades to anisometropic spectacles

Saccades are the rapid eye movements which enable us to voluntarily shift our gaze from one visual target to another. They serve to bring newly selected visual targets to the fovea of each of the two eyes, which is a small part of the retina with high visual acuity. This accurate, binocular control of saccades requires a high quality of oculomotor coordination. During the course of a lifetime, the various structures involved in the generation and the control of saccades may be subject to change, due to, for example, growth, ageing, disease or injury. These changes will undoubtedly affect saccadic control, and, consequently, jeopardize its quality. To safeguard its proper functioning, the oculomotor system will therefore have to adapt adequately to such changes. As these changes probably take place haphazardly, at different places, with different time-courses and with different degrees of severity, the saccadic subsystem should be capable of adapting specifically to such non-uniform changes. Adaptation of saccades has been described in the literature subsequent to local, physical damage to external eye muscles, as well as to purely visual stimuli (for a review, see Chapter 2). The aim of this thesis was to assess both qualitatively and quantitatively how the sa~cadic subsystem responds to a consistent visual pressure for an asymmetrical adaptation, i.e., adaptation that is different for each of the two eye

Upper eyelid motility in blepharoptosis and in the aging eyelid

PURPOSE. To study the metrics of lid saccades in blepharoptosis and to distinguish any differences in the dynamics of eyelid movements that are related to the cause of blepharoptosis and to aging. METHODS. The lid and vertical eye saccades of 7 patients with congenital blepharoptosis and those of 18 patients with aponeurogenic blepharoptosis, either involutional or rigid-contact-lens-induced, were recorded with electromagnetic search coils. For each saccade, two parameters were assessed: amplitude and peak velocity. Two age-matched control groups were assessed in the same manner. Repeated measures analysis of variance was used to investigate any observed differences between the included groups. RESULTS. Congenital and rigid-contact-lens-induced blepharoptosis were readily distinguishable from one another, as well as from the age-matched control group, in both lid saccadic amplitude and peak velocity. For example, 40 degrees downward lid saccades in the congenital blepharoptosis group averaged 22.9 degrees +/- 4.0 degrees (SD), whereas 30.0 degrees +/- 4.7 degrees lid saccades were made by the age-matched control group. The subjects in the two groups with aponeurogenic blepharoptosis also made lid saccades that were distinctive for their group (P: < 0.02), in both amplitude and peak velocity. For 40 degrees downward saccades in involutional and rigid-contact-lens-induced blepharoptosis, lid saccadic amplitude averaged 32.7 degrees +/- 4.3 degrees and 40.3 degrees +/- 3.5 degrees, respectively. Lid saccadic peak velocity declined significantly with age. Lid saccadic peak velocity for 40 degrees upward saccades in the younger control group averaged 401.7 +/- 11.4 deg/sec, whereas the older control group achieved an average peak velocity of 360.7 +/- 60.4 deg/sec. The lid saccadic dynamics in the involutional blepharoptosis group proved to be similar (P: > 0.05) in saccadic amplitude and peak velocity to those of age-matched controls. CONCLUSIONS. In diffe

Automated detection of wedge-shaped defects in polarimetric images of the retinal nerve fibre layer

Purpose: Automated glaucoma detection in images obtained by scanning laser polarimetry is currently insensitive to local abnormalities, impairing its performance. The purpose of this investigation was to tes