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Editors Selection IGR 15-4

Risk Factors for Glaucoma: Translaminar pressure gradient

Comment by John Berdahl on:

55630 Body height, estimated cerebrospinal fluid pressure and open-angle glaucoma. The Beijing Eye Study 2011, Jonas JB; Wang N; Wang YX et al., PLoS ONE, 2014; 9: e86678

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Over the last five years, much time, effort, thought and research has been put into the role that cerebrospinal fluid pressure (CSFP) plays in the pathogenesis of glaucoma. Numerous prospective and retrospective studies have shown that a low CSF pressure is more common in patients with glaucoma and normal-tension glaucoma, while an elevated CSF pressure is associated with patients that have ocular hypertension, but no glaucomatous disease. One of the major challenges of investigating this theory is the difficult nature of obtaining safe and accurate CSF pressure measurements. Traditionally, lumbar puncture in the lateral decubitus position has been the preferred method for determining cerebrospinal fluid pressure, however, there are many questions regarding if a lumbar puncture can adequately represent the CSF pressure at eye level. Jonas et al. have done work showing that estimation of CSF pressure can be used with a formula of 0.44 x BMI + 0.16 x diastolic blood pressure ‐ 0.18 x age ‐ 1.91. Of course, this is only an estimation of CSF pressure, but using this estimation may help us stratify patients' glaucoma risk better.

In this study, the authors attempted to determine if an association between body height, estimated CSFP, and open-angle glaucoma existed; and they found that a taller body height was associated with a higher CSF pressure and a lower pressure difference across the lamina cribrosa. Additionally, they found a higher prevalence of glaucoma with a lower estimated CSF pressure or higher translaminar pressure difference. This study was performed in nearly 3500 individuals in the Beijing Eye Study.

The great challenge to this type of study is if estimated CSF pressure can truly be relied upon as a surrogate for actual CSF pressure. Of course this is yet to be definitely shown; however, Jonas and colleagues have analyzed a lot of data to create this formula. Another challenge in a study like this is that BMI already has a factor in it for a person's body height. With those two caveats, I applaud the efforts of Jonas and his team to find a creative way to investigate the role of CSF pressure and glaucoma knowing that it is otherwise a great difficult measurement to obtain, especially as it relates to eye and the CSFP at eye level. The clinical implications of this study that low CSFP is associated to higher prevalence of glaucoma and clinicians should continue to be aware that a low CSF pressure may be important in the pathogenesis of glaucoma, especially normal-tension glaucoma.

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