Abstract
Purpose: :
To investigate the load and unload behaviour of the peripapillary sclera canal ring (scr) and a superiorly localized sclera ring (sps) in the porcine eye.
Methods: :
Two sclera rings were trephined from each of 40 porcine eyes, one containing the sclera canal ring and the other a more superiorly localized sclera ring. The load and the unload curve were measured in the extension range of 0 to 2.0 mm by a biomaterial tester. Hysteresis was determined from the area enclosed by the loading and unloading curve.
Results: :
At 1 mm extension the mean load of the scr was 0.89 ± 0.22 N and 1.13 ± 0.19 N in the sps which was not significantly different between both rings (P= 0.05). Mean hysteresis in the scr was 1.55 ± 0.30 N x mm and 1.90 ± 0.18 N x mm in the sps which was significantly different between both rings (P=0.01). Mean sclera thickness was 986 µm in the scr (range: 900 µm-1060 µm) and 971 µm in the sps (range: 800 µm -1200 µm) without a statistical significant difference between both sclera rings (P=0.78).
Conclusions: :
Hysteresis in the scr was significantly lower than in the sps indicating a higher elasticity of the scr in the porcine eye. This effect could be explained by a higher content of elastin in the surrounding ring of the peripapillary optic nerve head providing reversible contraction in cases of IOP variations.