Congenital nystagmus (CN) is an ocular-motor disorder that appears at birth or during the first few months of life; it is characterised by involuntary, conjugated, bilateral to and fro ocular oscillations mainly horizontal. Pathogenesis of congenital nystagmus is still unknown. In general, CN patients show a considerable decrease of the visual acuity: image fixation on the retina is disturbed by nystagmus continuous oscillations; however, image stabilisation is still achieved during the short periods in which eye velocity slows down while the target image is placed onto the fovea (foveation intervals) [1]. To quantify extent of nystagmus, eye movement recording are routinely employed, allowing physicians to extract and analyse nystagmus main features such as shape, amplitude and frequency. Eye movement recording study leads to the computation of estimated visual acuity predictors; their use could integrate usual visual acuity measurement, such as Landolt C test, and could be a support for therapy planning or monitoring [2,3,4]. This study concentrates on identification of the foveation in CN eye-movement recordings, and proposes a method to recognize signal tracts in which a subject foveates, that is the time in which eye position is confined within ±0.5 degree from the local foveation point, while velocity is lower than 4 degree/s (the so called foveation window).
Estimation of foveation windows in congenital nystagmus eye movements recordings
M. Romano;
2008-01-01
Abstract
Congenital nystagmus (CN) is an ocular-motor disorder that appears at birth or during the first few months of life; it is characterised by involuntary, conjugated, bilateral to and fro ocular oscillations mainly horizontal. Pathogenesis of congenital nystagmus is still unknown. In general, CN patients show a considerable decrease of the visual acuity: image fixation on the retina is disturbed by nystagmus continuous oscillations; however, image stabilisation is still achieved during the short periods in which eye velocity slows down while the target image is placed onto the fovea (foveation intervals) [1]. To quantify extent of nystagmus, eye movement recording are routinely employed, allowing physicians to extract and analyse nystagmus main features such as shape, amplitude and frequency. Eye movement recording study leads to the computation of estimated visual acuity predictors; their use could integrate usual visual acuity measurement, such as Landolt C test, and could be a support for therapy planning or monitoring [2,3,4]. This study concentrates on identification of the foveation in CN eye-movement recordings, and proposes a method to recognize signal tracts in which a subject foveates, that is the time in which eye position is confined within ±0.5 degree from the local foveation point, while velocity is lower than 4 degree/s (the so called foveation window).I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
