Eye viscosity increases with age

According to a paper published in Clinical and Experimental Ophthalmology, loss of energy due to elastic hysteresis positively correlates with age, leading to the belief that eye viscosity increases with age.

Dr K. Ishii et al., Department of Ophthalmology, Institute of Clinical Medicine, University of Tsukuba, Ibaraki, Tokyo, Japan, included 24 eyes of 24 normal human patients in a prospective case series.

The non-contact tonometry procedure was conducted with a high-speed camera. The outcome measures were central corneal thickness (CCT), corneal thickness at 4 mm from the centre, corneal curvature and anterior chamber depth (ACD). IOP was also recorded using Goldmann applanation tonometry (GAT) and dynamic contour tonometer (DCT). The primary outcome measure was energy loss due to elastic hysteresis.

Mean CCT was 552.5 ± 36.1 µm, mean corneal curvature was 7.84 ± 0.26 mm and ACD was 2.83 ± 0.29 mm. Mean GAT-IOP was calculated as 14.2 ± 2.7 mmHg and DCT-IOP was 16.3 ± 3.5 mmHg.

The mean loss of energy due to elastic hysteresis was 3.90 × 10(-6) ± 2.49 × 10(-6) Nm and this was significantly linked to age, regardless of anterior eye structure or IOP.

The abstract for this study can be found here.