This structure is a major player in glaucoma, and the importance of determining why it is vulnerable to pressure, among other forces, cannot be overemphasized. Computational modeling of the ONH predicts high mechanical strains in the ONH tissues, indicating that the ONH is a weak spot in the otherwise tough corneoscleral shell, Dr. Ethier demonstrated.
Experimentally, micro-computed tomography 3-D imaging of the ONH region of an enucleated porcine eye showed the strains that occurred when the eye was subjected to different IOP levels. For example, the anterior and posterior lamina cribrosa within the ONH undergo significant stretching and compression as IOP increases, corresponding to deformations thought to exceed safe ranges that the cells can tolerate.
Cerebrospinal fluid pressure also can affect strains in the ONH. “We know that when looking at the average or peak strains in the lamina cribrosa or in the retrolaminar neural tissue just posterior to the lamina, the strains are well outside of the safe ranges, especially in the retrolaminar neural tissue,” Dr. Ethier said.