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Editors Selection IGR 15-4

Clinical Forms of Glaucoma: Normal Pressure Glaucoma

Comment by Jost Jonas on:

66233 Estimated Trans-Lamina Cribrosa Pressure Differences in Low-Teen and High-Teen Intraocular Pressure Normal Tension Glaucoma: The Korean National Health and Nutrition Examination Survey, Lee SH; Kwak SW; Kang EM et al., PLoS ONE, 2016; 11: e0148412

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The lamina cribrosa in the optic nerve head is the site where the glaucomatous damage to the optic nerve fibers presumably occurs. In the lamina cribrosa, the pressure changes from the level of the intraocular compartment, i.e., the intraocular pressure, to the level of the retrobulbar compartment, i.e., the tissue pressure of the optic nerve and the orbital cerebrospinal fluid pressure (CSFP). Since the orbital CSFP is one of the determinants of the trans-lamina cribrosa pressure difference (TLCPD), the hypothesis was proposed that a low orbital CSFP may play a role in the pathogenesis of glaucomatous optic neuropathy, in particular in patients with normal-(intraocular-)pressure glaucoma.

Since the CSFP cannot be measured directly and non-invasively, attempts have been made to estimate it based on formulas which take into account the dependence of the CSFP on blood pressure, body mass index and age. Using such a formula, Lee and colleagues have calculated the CSFP in a large group of individuals without and with glaucoma. They found that the calculated TLCPD was significantly higher in patients with normal-pressure glaucoma and IOPs in the high teens compared to normal subjects. In contrast, there was no difference in calculated TLCPD for patients with normal-pressure glaucoma and IOPs in the low teens compared with normal subjects.

The study partially supports, but also partially may contradict, the concept of low CSFP in the pathogenesis of glaucoma. A major limitation of the study, however, is that the formulas for the estimation of CSFP have not yet been validated. This highlights the importance of developing new techniques for the non-invasive measurement of the CSFP, for ophthalmology as well as for neurology.

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