Elastic hysteresis in human eyes is age dependent value

Area of Science:

• Ophthalmology
• Biomechanics
• Ocular Viscoelasticity

Background:

• Elastic hysteresis is a phenomenon observed in viscoelastic systems under cyclic loading.
• Understanding ocular viscoelasticity is crucial for interpreting tonometry measurements.
• Previous studies have not quantitatively assessed elastic hysteresis in living human eyes.

Purpose of the Study:

• To quantitatively evaluate elastic hysteresis in living human eyes.
• To determine the relationship between elastic hysteresis and ocular parameters.
• To investigate the influence of age on ocular elastic hysteresis.

Main Methods:

• A prospective case series involving 24 normal human subjects.
• High-speed videography of non-contact tonometry.
• Measurements included central corneal thickness (CCT), corneal curvature, anterior chamber depth (ACD), and intraocular pressure (IOP) via Goldmann applanation tonometry (GAT) and dynamic contour tonometer (DCT).

Main Results:

• Mean CCT: 552.5 ± 36.1 µm; Mean corneal curvature: 7.84 ± 0.26 mm; Mean ACD: 2.83 ± 0.29 mm.
• Mean GAT-IOP: 14.2 ± 2.7 mmHg; Mean DCT-IOP: 16.3 ± 3.5 mmHg.
• Mean energy loss due to elastic hysteresis: 3.90 × 10⁻⁶ ± 2.49 × 10⁻⁶ Nm. This energy loss significantly correlated with age (r=0.596, p=0.0016).

Conclusions:

• Energy loss due to elastic hysteresis in human eyes positively correlates with age.
• This age-related increase in hysteresis is independent of anterior eye structure and intraocular pressure.
• The findings suggest an increase in ocular viscosity with advancing age.