The relationship between two types of upper eyelid movements: saccades and pursuit
Marcele Falcao 1,
Jorge M Malbouisson 2,
Antonio A.V. Cruz 3*,
and
Andre Messias 1
1 Ophthalmology, School of Medicine of Ribeirao Preto- University of Sao Paulo, Ribeirao Preto, Sao Paulo, Brazil
2 Physics, Federal University of Bahia, Salvador, Bahia, Brazil
3 Ophthalmology, School of Medicine of Ribeirao Preto- University of Sao Paulo, Ribeirao Preto, Brazil
* To whom correspondence should be addressed. E-mail: aavecruz{at}fmrp.usp.br.
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Abstract |
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Purpose. To establish the relationship between upper eyelid saccades and upper eyelid pursuit movements
Methods. Upper eyelid saccades and periodic sinusoidal upper eyelid pursuit movements were recorded in a sample of controls and patients with Graves upper eyelid retraction. A video computerized system was used to register both types of movements that accompanied 60° of eye rotation across the upper and lower hemifields. The forced harmonic oscillator model was used to fit both saccadic and pursuit movements.
Results. The mean mid-pupil eyelid distance for the Graves patients (6.6 ± 1.1 mm) was significantly higher for the controls (4.6 ± 0.8 mm) t = 7.18; p < 0.00001. Despite the difference in the upper eyelid resting position, saccades and pursuit eyelid movements of both groups were extremely well fitted by underdamped solutions and steady forced solutions of the harmonic oscillator model, respectively. For the controls the amplitude of the pursuit movements were well correlated with the upward and downward saccades. The amplitude of the eyelid movements of the Graves patients (saccades and pursuit) was significantly reduced compared to the controls.
Conclusions. Saccadic and pursuit movements of the upper eyelid can be described by the harmonic oscillator model. In normal subjects and Graves patients the amplitude of pursuit lid movements are correlated to the saccade amplitude. Pursuit eyelid movements are more difficult to register than saccades and their measurement do not allow a clear separation of the relaxation and contraction properties of the upper eyelid retractors.
Key Words:
Graves- disease, eyelid movements, saccades, pursuit
