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Changes in cyclotorsion and vertical eye alignment during prolonged monocular occlusion.
Erich W Graf1, James S Maxwell, Clifton M Schor
1Vision Science Group, Department of Optometry, University of California-Berkeley, 360 Minor Hall, Berkeley, CA 94720-2020, USA.
Vision Research
|May 9, 2002
Summary
Prolonged monocular occlusion causes excyclophoria (outward eye turn) and independent vertical eye position changes. These findings suggest excyclophoria may be the natural resting state for binocular alignment.
Area of Science:
- Ophthalmology
- Neuroscience
- Biomechanics
Background:
- Binocular vision relies on complex oculomotor control.
- Monocular occlusion can reveal underlying resting eye positions (phorias).
- Previous studies noted outward (exophoria) and upward (hyperphoria) deviations after occlusion.
Purpose of the Study:
- To investigate changes in torsional (rotational) eye alignment.
- To examine the relationship between torsional and vertical eye alignment after prolonged monocular occlusion.
- To explore the potential biomechanical basis of observed phoria changes.
Main Methods:
- Monocular occlusion applied for eight hours.
- Measurement of torsional and vertical eye alignment during occlusion.
- Utilized Orbit(TM) simulations for biomechanical analysis.
Main Results:
- Four out of five subjects developed excyclophoria during occlusion.
- Vertical eye alignment changes (elevation/depression) were independent of cyclophoria direction.
- Non-concomitant vertical phoria changes with horizontal gaze were observed.
Conclusions:
- Prolonged monocular occlusion induces excyclophoria and independent vertical phoria shifts.
- Orbital mechanics may explain the observed non-concomitant vertical phoria and excyclophoria.
- Excyclophoria appears to be the baseline state of binocular alignment.