Figure 3.

Effects of intraocular pressure (IOP) increase on non-human primates. (A and B) The acute effects of (A) 10 mm Hg (top) and (B) 45 mm Hg (bottom) IOP on spectral domain optical coherence tomography (SD-OCT) B-scans of a normal monkey eye. Bruch's membrane (red dots) and the anterior lamina cribrosa (LC) surface (green dots) have been delineated. The area enclosed by the anterior surface of the LC and a plane defined at Bruch's membrane opening (area shaded green) is larger in the scan at 45 mm Hg. There was no detectable lateral expansion of the scleral canal at Bruch's membrane opening (vertical green lines). Using a second reference plane parallel to BM opening (dashed red lines), it is also visible that the BM is outwardly bowed at high IOP, which suggests that there is IOP-induced posterior deformation of the peripapillary sclera. While choroidal compression may contribute to this finding, we believe that the behaviour of BM is principally related to the behaviour of the sclera. (C) The chronic effects of IOP elevation on the morphology and position of the internal limiting membrane and anterior surface of the LC are compared in an early glaucoma monkey eye. (D) Anterior LC surface and neural canal opening at baseline (green), follow-up 1 (yellow) and follow-up 2 (red). Delineations were made on images acquired with SD-OCT. Adapted with permission from Sigal et al⁴⁶ and Strouthidis et al.²⁷