Abstract
Purpose :
Although a dense elastin ring encircling the lamina cribrosa and fine elastin fibers circumferential to the peripapillary sclera have been described, few details are known about development and distribution of elastin deposits (ED) in the posterior sclera more remote from the optic nerve (ON) head that may be important to the biomechanics of optic neuropathy. This study characterized such ED in the human posterior sclera.
Methods :
8 whole orbits ages 33 wks fetal life to 93 ys, and posterior scleras of 3 whole globes with optic nerves were formalin fixed, paraffin embedded, stained with van Giesson elastin stain and serially sectioned in the coronal plane at 10μm thickness. We analyzed sections 1 mm anterior to 1mm posterior to the globe-ON junction at 0.2 mm intervals. Morphometry of ED was performed using Adobe Photoshop and ImageJ.
Results :
In adults, dense ED with areas ranging from 0.003-0.044 mm2 were widely dispersed 0.3 to 5.6 mm from the globe-ON junction. The ED had a non-uniform laminar distribution embedded in the circumpapillary sclera and differ from previously described elastin fibers encircling the ON or those associated with blood vessels or nerves. The ED occur in the circumlaminar sclera around the lamina cribrosa and extend up to 0.8 mm anteriorly into the circumpapillary sclera. 10±4% of total ED were radially dispersed within 1 mm, 70±3% 2-4 mm, and 20±4% >4 mm from the globe-ON junction. There were no dense ED in the 3 non-adult orbits, or in the optic nerve dural sheath of any specimen.
Conclusions :
Dense, focal masses of elastin develop after childhood and are predominantly embedded in the adult sclera 2 – 4 mm from the ON head just peripheral to the circumpapillary elastic ring. These ED may alter the biomechanical properties of the circumpapillary and posterior sclera, and might be induced by repetitive strain in this normally mechanically pliable region when subjected ON traction during eye movements.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.