Analysis of foveation sequences in congenital nystagmus

Giulio Pasquariello*, P. Bifulco, M. Cesarelli, M. Romano, A. Fratini

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference publication

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. Pathogenesis of congenital nystagmus is still unknown. Eye movement recording allow to extract and analyse nystagmus main features such as shape, amplitude and frequency; depending on the morphology of the oscillations nystagmus can be classified in different categories (pendular, jerk, horizontal unidirectional, bidirectional). In general, CN patient 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 foveation periods in which eye velocity slows down while the target image is placed onto the fovea. Visual acuity was found to be mainly dependent on foveation periods duration, but cycle-to-cycle foveation repeatability and reduction of retinal image velocities also contribute in increasing visual acuity. This study concentrate on cycle-to-cycle image position variation onto fovea, trying to characterise the sequences of foveation positions. Eye-movement (infrared oculographic or electro oculographic) recordings, relative to different gaze positions and belonging to more than 30 CN patients, were analysed. Preliminary results suggest that sequences of foveations show a cyclic pattern with a dominant frequency (around 0.3 Hz on average) much lower than that of the nystagmus (about 3.3 Hz on average). Sequences of foveations reveals an horizontal ocular swing of more than 2 degree on average, which can explain the low visual acuity of the CN patient. Current CN therapies, pharmacological treatment or surgery of the ocular muscles, mainly aim to increase the patient's visual acuity. Hence, it is fundamental to have an objective parameter (expected visual acuity) for therapy planning. The information about sequences of foveations can improve estimation of patient visual acuity.

Original languageEnglish
Title of host publication14th Nordic-Baltic Conference on Biomedical Engineering and Medical Physics
Subtitle of host publicationNBC 2008 16–20 June 2008 Riga, Latvia
EditorsAlexei Katashev, Yuri Dekhtyar, Janis Spigulis
Place of PublicationBerlin (DE)
PublisherSpringer
Pages303-306
Number of pages4
ISBN (Electronic)978-3-540-69367-3
ISBN (Print)978-3-540-69366-6
DOIs
Publication statusPublished - 2008
Event14th Nordic-Baltic Conference on Biomedical Engineering and Medical Physics - Riga, Latvia
Duration: 16 Jun 200820 Jun 2008

Publication series

NameIFMBE proceedings
PublisherSpringer
Volume20
ISSN (Print)1680-0737

Conference

Conference14th Nordic-Baltic Conference on Biomedical Engineering and Medical Physics
Abbreviated titleNBC 2008
CountryLatvia
CityRiga
Period16/06/0820/06/08

Keywords

  • congenital nystagmus
  • eye movement signal processing
  • foveation
  • visual acuity

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  • Muscle movement and electrodes motion artifact during vibration treatment

    Fratini, A., Bifulco, P., Cesarelli, M., Romano, M., Pasquariello, G., la Gatta, A. & Gargiulo, G., 2008, 14th Nordic-Baltic Conference on Biomedical Engineering and Medical Physics: NBC 2008 16–20 June 2008 Riga, Latvia. Katashev, A., Dekhtyar, Y. & Spigulis, J. (eds.). Berlin (DE): Springer, p. 103-106 4 p. (IFMBE proceedings; vol. 20).

    Research output: Chapter in Book/Report/Conference proceedingConference publication

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