Jonas et al. examined whether an estimated trans-lamina cribrosa pressure difference (TLCPD), which was based on the body mass index, diastolic blood pressure and age, correlated with markers for glaucoma better than intraocular pressure (IOP). They found that open-angle glaucoma (OAG) was associated with higher TLCPD but not with IOP. In addition, retinal nerve fiber layer thickness was associated with lower TLCPD but not with IOP. Taken together, TLCPD as compared with IOP was better associated with the presence of open angle glaucoma and with the amount of glaucomatous optic nerve damage. The results of this study are in line with the previous studies and support that low orbital cerebrospinal fluid pressure may play a role in the pathogenesis of glaucomatous optic neuropathy. Stronger association of TLCPD than IOP was not observed with angle closure glaucoma, which is generally considered to be derived from pure IOP elevation.
Primary open-angle glaucoma is a multifactorial disease, in which various parameters are considered to be involved. Although elevated IOP is a well-known risk factor for primary OAG, it is frequent to see patients with IOP within the statistically normal range. It is not uncommon to see large backward bowing of the lamina cribrosa in those patients as is in patients with high tension glaucoma.1 One may hypothesize that lower orbital cerebrospinal fluid pressure may be related with this phenomenon by facilitating the posterior displacement of the lamina cribrosa by the IOP-induced mechanical stress. Although the individual variation of true orbital CSF pressure is currently unknown as it is not currently measurable, one may consider the possibility that the IOP-induced mechanical stress may still play a significant role in the optic nerve damage even in eyes with low IOP. Low CSF pressure may be one factor that makes this scenario possible.