The thickness of the sclera has been morphologically examined in 165 cadaver eyes and the thickness of the reticular plate (RP) in 68 eyes in open-angle glaucoma, atherosclerosis, and involution. The measurements have shown that the sclera and RP are thinner in atherosclerosis than in the control, this process being more manifest in the RP. The RP supporting characteristics deteriorate even in vascular abnormalities. Open-angle glaucoma is associated with a most significant thinning of the sclera (t up to 5.33), but when this process develops far, the thinning ceases (t = 0.06). RP thinning is more marked (t = 2.2 = 7.58) and does not cease in case of a far-developed process. The values of the pressure on the posterior segment of the eye in health and in glaucoma are presented; this pressure is drastically elevated in glaucoma, which fact may explain the stretching of the entire posterior segment (of the sclera by 1.5 times and of the RP by 8.5 times). Since the mechanical properties of the RP are poor and the plate virtually disappears, the optic nerve is devoid of its support.