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E. A. Arkenbout, N. J. van de Berg, R. J. Visser, S. Schutte, F. C. T. van der Helm, W. A. van den Bosch, H. J. Simonsz; Eyelid Pressure Measurements for Early Diagnosis. Invest. Ophthalmol. Vis. Sci. 2008;49(13):5265.
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In surgical correction of eyelid disorders the technique chosen may depend on lid laxity. By determining the eyelid stiffness and its lid pressure on the sclera an early and efficient analysis can be made to diagnose the state of the patients’ eyelid.
For determining the eyelid pressure Peye and the prestress force Flid two tests have been designed. Peye is measured by placing a small sensor under the lid. The sensor is based on strain gauges placed on a small beam. Flid is measured as the force required too stretch the lid anteriorly. Measurements have been collected from volunteers from our department, all Caucasian. A theoretical model has been made in MATLAB in order to interpret the measured values of Peye with Flid and to increase the understanding of the lids mechanical properties. By determining these variables the model can be validated.
Pressure exerted by the lid perpendicular to the sclera showed considerable varying data around 0.04N. To measure Flid a small clamp was placed on the eyelashes and an anterior translation up to 5mm was exerted by a stepper motor. Among the volunteers there were 16 subjects in the age range 18-25 and 6 subjects in the age range of 40-60. The relation between force and translation showed a transition from a linear to an exponential relation for all subjects. The data from one representative individual from each age range has been plotted in the graph. The theoretical model is based on the geometry of the eyelid and its attachment points relative to the geometry of the eyeball. Assumptions made are an undeformable eyeball and an equally distributed eyelid pressure on the tarsus-covered sclera.
The initial results show no significant difference in lid prestress force between the older and younger subjects. Because eyelid laxity problems are rather expected in patients over age 65 additional measurements will be performed in this age category.
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