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Editors Selection IGR 12-1
Clinical Examination Methods: Translaminar pressure gradient
Comment by Sung-Chul Park on:
57451 Estimated trans-lamina cribrosa pressure difference versus intraocular pressure as biomarker for open-angle glaucoma. The Beijing Eye Study 2011, Jonas JB; Wang NL; Wang YX et al., Acta Ophthalmologica, 2015; 93: e7-e13
See also comment(s) by Tae-Woo Kim •Cerebrospinal fluid (CSF) has been implicated in the pathogenesis of primary open-angle glaucoma (POAG). Low CSF pressure[1-3] and stagnated CSF around the optic nerve head[4,5] have been demonstrated in eyes with POAG. Theoretically, lower CSF pressure may result in greater trans-lamina cribrosa pressure difference (TLCPD) and consequently greater stress and strain in the lamina cribrosa, contributing to development and progression of glaucomatous optic neuropathy.
Jonas et al. investigated the association between TLCPD and presence/severity of OAG and angle-closure glaucoma (ACG), by calculating the CSF pressure using an equation derived from a previous study. They found that the presence/severity of OAG was more strongly associated with TLCPD than with intraocular pressure (IOP), whereas the presence/ severity of ACG was associated only with IOP. As acknowledged by the authors, this study is limited by the use of calculated CSF pressure, not directly measured one.
The thickness, density and rigidity of the lamina cribrosa and surrounding sclera will influence the physical/biological changes in the lamina cribrosa associated with TLCPD
Additionally, because both eyes of subjects were included in the analysis, it is possible that the data from one eye were included in the glaucoma group and the data from the fellow eye were included in the non-glaucoma group, while the body-mass-index and blood pressure data of the subject were used in both glaucoma and non-glaucoma groups.
Despite these limitations, the authors' findings are informative and warrants more elaborate investigations on the role of CSF pressure in the glaucoma pathophysiology. Various noninvasive methods to measure the CSF pressure have been suggested including untrasound time of the flight techniques, transcranial Doppler ultrasonography, and tympanic membrane displacement, but more reliable and reproducible method to measure the CSF pressure is needed considering that CSF pressure measured by lumbar puncture may be different from the CSF pressure around the optic nerve head. Investigators should also consider that similar TLCPD does not necessarily mean similar stress and strain in the lamina cribrosa. For example, an eye with TLCPD of 10 mmHg may have IOP of 15 mmHg and CSF pressure of 5 mmHg, or IOP of 30 mmHg and CSF pressure of 20 mmHg. Additionally, the thickness, density and rigidity of the lamina cribrosa and surrounding sclera will influence the physical/biological changes in the lamina cribrosa associated with TLCPD.
References
- Yablonski M, Ritch R, Pokorny KS. Effect of decreased intracranial pressure on optic disc. Invest Ophthalmol Vis Sci 1979;18 (Suppl):165.
- Berdahl JP, Allingham RR, Johnson DH. Cerebrospinal fluid pressure is decreased in primary open-angle glaucoma. Ophthalmology 2008;115:763-768.
- Ren R, Jonas JB, Tian G et al. Cerebrospinal fluid pressure in glaucoma. A prospective study. Ophthalmology 010;117:259-266.
- Killer HE, Miller NR, Flammer J, et al. Cerebrospinal fluid exchange in the optic nerve in normal-tension glaucoma. Br J Ophthalmol 2012;96:544-548.
- Killer HE. Compartment syndromes of the optic nerve and open-angle glaucoma. J Glaucoma 201;22(Suppl 5):S19-S20.
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