Evaluation and clinical significance of the mechanical properties of various palpebral springs.
Fourteen different wire materials were evaluated for use as palpebral springs. Three of these, stainless steel 0.010- and 0.012-in diameter, respectively, and Australian stainless steel 0.012-in diameter, fulfilled the designated criteria for suitability. The physiologic deflection range of palpebral springs was determined by examining 20 normal individuals. Angles that a spring would subtend were measured with eyes closed (42 +/- 3 degrees), in primary position (20 +/- 3 degrees), and in upgaze (6 +/- 3 degrees). The effects of spring design on load-deflection (the force required for angular deflection) were evaluated for 0.010- and 0.012-in stainless steel wire within the physiologic deflection range. Variations in spring design in addition to wire diameter (gauge) included alteration of external loop size, number of external loop coils, and resting spring angle. There was a direct linear relationship between force and angular deflection (load-deflection). Larger wire diameter increased the load-deflection. Australian stainless steel had a higher load deflection (stiffer) for a given gauge than regular stainless steel. Smaller diameter external loops and fewer external loop coils increased load-deflection. Although definite conclusions could not be drawn regarding the effect of resting angle on load-deflection, it appeared that no relationship (zero correlation) existed over the angles tested (55 degrees, 60 degrees, 65 degrees, 70 degrees, 75 degrees). These findings were consistent with predictions based on standard spring equations. The clinical significance of the findings is discussed with reference to surgical planning and evaluation of lid dynamics.
Cartwright
M J
MJ
Florida Eye Clinic, Altamonte Springs 32701, USA.
Frueh
B R
BR
D000293:Adolescent; D000328:Adult; D001696:Biomechanical Phenomena; D001767:Blinking / Q000502:physiology*; D001864:Bone Wires; D005069:Evaluation Studies as Topic; D005141:Eyelid Diseases / Q000503:physiopathology / Q000601:surgery; D005143:Eyelids / Q000502:physiology* / Q000601:surgery; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013193:Stainless Steel; D013314:Stress, Mechanical
D013193:Stainless Steel