Mechanical Properties of Vitreous Humor in Eye Pairs

Abstract

 

Purpose

 

To investigate the possibility of bilateral symmetry in the viscoelastic properties of the porcine vitreous humor.

 

Methods

 

Bilateral porcine eyes were obtained from Sierra for Medical Science (Whittier, CA) within 10 hours post mortem (four animals, n=8). For each sample a 2 mm cross slerotomy was made in the sclera 3 mm posterior to the limbus. A 1.7 mm diameter cylindrical probe attached to an AR2000 rheometer was subsequently inserted 7 mm into the vitreous cavity via the sclerotomy. The creep compliance of the vitreous samples was obtained by setting the rheometer to apply a constant 1 μNm torque for 300 seconds and record the rotational displacement of the rod.

 

Results

 

Creep compliance is the quotient of the strain of a material and the constant stress applied. Figure 1 shows the creep compliance of four porcine eye pairs as a function of time under stress. The plateau compliance (i.e. the value at which the plot begins to flatten) is characteristic of the inverse of the elasticity or stiffness of the vitreous humor. By inspection, the plateau compliance as well as the general trends of the compliance plots are very similar for the paired eyes of individual animals. There exists, however, distinct differences between those values of the different animals. In fact, there was only a 0.01 ± 0.004 1/Pa average difference in plateau compliance within the pairs but a 0.178 ± 0.043 1/Pa average difference between the pairs.

 

Conclusions

 

We found a clear similarity between the viscoelastic responses of the vitreous humor in the right and left eye of a pair. This similarity may have some clinical correlation with bilateral vitreoretinal pathologies.

 

 

Keywords: 763 vitreous • 762 vitreoretinal surgery