Abstract
Purpose :
The rheological behavior of soft tissues subjected to shear loading may be characterized by strain sweep, cyclic, stress failure, stress relaxation, and creep testing, but to date none of these have been described for human orbital fat.
Methods :
Fresh human orbital fat was obtained as byproduct of globe harvest from the Minnesota Lions Gift of Sight Eye Bank from of 5 males and 6 females of average age 77±12 years and transported on saline-soaked gauze. Some connective tissue was intrinsic within orbital fat and was not separable. Specimens were cut into 2mm thick disks 20mm in diameter. Specimens were placed between plates of an AR 2000 torsional rheometer (TA Instrument Inc., New Castle, DE) maintained at 37 with an oil seal applied to disc margins to prevent dehydration. Eight specimens each were subjected to 1 Hz cyclic strain sweep from 0.0015m to 150%, stress loading to failure at 0.1/s strain rate, stress relaxation after application of 0.5% strain within 0.01s, and creep under 10 Pa stress maintained after 0.01s that is within the linear viscoelastic limit. All Specimens were preconditioned for 3s under 1 Hz, 0.005% cyclic strain.
Results :
Human orbital fat displayed linear viscoelasticity up to 0.5% strain, above which shear thinning occurred. Rupture stress averaged 617±366 Pa (SD). Average relaxation modulus, GE reached 690 Pa after 90s. During creep testing, a steady state condition representing liquid-like behavior was evident after about 250s). Creep compliance, J was 0.006 Pa-1.
Conclusions :
Human orbital fat is linearly viscoelastic up to 0.5% shear strain. Rheological characteristics of human orbital fat resemble bovine orbital fat as described by Yoo et al. (Biomech Model Mechanobiol 2011;10:901-914) These results should be useful in modeling eye movements where orbital fat plays an important role in supporting the eye.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.