Morphological Changes of the Retrobulbar Optic Nerve and Its Meningeal Sheaths in Glaucoma

Abstract

This work focuses on the possible remodeling of the intraorbital portion of the optic nerve and its meningeal sheaths in glaucoma. The bulbar segments of the orbital optic nerve portion from 25 donors with glaucoma (M:F = 8:17; mean age ± SD 85 ± 11 years) and 25 controls (M:F = 14:11; mean age ± SD 81 ± 8 years) were formalin fixed, paraffin embedded and sectioned in series. Sections were stained with PAS, Masson trichrome and CD68, and examined for the following parameters: (1) diameter of the optic nerve; (2) thickness of the pia mater; (3) distance between dura mater and pia mater; (4) occurrence and amount of meningothelial cell nests in the subarachnoid space, and (5) presence and number of corpora arenacea. The mean diameter of the optic nerve was decreased in the glaucoma group when compared to the controls (2.9 ± 0.5 vs. 3.3 ± 0.5 mm; p < 0.01). The thickness of the pia mater was increased in the glaucoma group (0.1 ± 0.04 vs. 0.09 ± 0.03 mm, p < 0.05). Presence and number of corpora arenacea did not differ between the groups. Occurrence and amount of meningo- thelial cell nests in the subarachnoid space were however significantly increased in glaucoma (p < 0.02). Whether this observation is glaucoma specific deserves further investigation.

The Role of Cerebrospinal Fluid Pressure in Glaucoma Pathophysiology: The Dark Side of the Optic Disc

“…59 It is interesting to speculate whether changes in the damping characteristics of the RLTP by alterations in pia mater compliance or orbital tissue pressure may alter likelihood for the development of glaucoma. A slight pia mater thickening from 10 to 11 mm has been found in glaucoma, 8 but its significance and the presence of any other pial changes is unknown. Optic nerve diameter is reduced in glaucoma, 8 lowering the volume within the pia mater raising the possibility that the pia mater is under reduced tension and hence transferring a smaller pressure increment into the retrolaminar tissue.…”

“…A slight pia mater thickening from 10 to 11 mm has been found in glaucoma, 8 but its significance and the presence of any other pial changes is unknown. Optic nerve diameter is reduced in glaucoma, 8 lowering the volume within the pia mater raising the possibility that the pia mater is under reduced tension and hence transferring a smaller pressure increment into the retrolaminar tissue. No studies have been published regarding orbital tissue pressure in glaucoma patients.…”

“…7 In human eyes, the posterior pia mater averages 10 mm in thickness. 8 Numerous trabeculae span the ONSAS from pia mater to the dura mater peripherally (Fig. 2).…”

Primary cell culture of meningothelial cells—a new model to study the arachnoid in glaucomatous optic neuropathy

“…A variety of trabecules and septae covered with meningothelial cells transverse the subarachnoid space between the arachnoid and the pia. Located between the dura and the arachnoid mater is the subdural space [1,2].The subdural and the subarachnoid space of the optic nerve are continuous with those of the brain.…”

“…A significant increase in occurrence and size of those meningothelial cell nests in the subarachnoid space has been observed in glaucoma compared to healthy optic nerves. The function is yet not known; however, a secondary reaction of the meningothelial cells to axon loss during glaucoma can be assumed [1]. In addition, impairment of meningothelial cell layer function might result in the failed clearance of biologically active molecules or waste products from the subdural and subarachnoidal space, and this might contribute to optic nerve diseases such as progressive anterior and posterior ischemic optic neuropathy, or optic nerve sheath compartment syndrome and even glaucoma [4,[6][7][8].…”