Authors’ Reply

Natasha F S Cruz1, MD; Katia S Santos1, MD; Mateus L Matuoka1, MD; Niro Kasahara1,2, MD

1Department of Ophthalmology, Irmandade da Santa Casa de Misericordia de Sao Paulo, Sao Paulo, Brazil
2Santa Casa de Sao Paulo School of Medical Sciences, Sao Paulo, Brazil.

ORCID:
Natasha Cruz: https://orcid.org/0000-0002-5209-9204
Niro Kasahara: https://orcid.org/0000-0003-4101-0304

J Ophthalmic Vis Res 2022; 17 (4): 603–604

Dear Editor,

We appreciate D. Fleischman’s comments on the
recent article by Cruz et al.[1] We deeply respect the
colleague’s opinion on the subject.

The first mention of an algorithm for the
estimation of the cerebrospinal fluid pressure
(CSFP) appeared in the prospective observational
comparative study by Xie et al.[2] The authors
included 72 neurology patients who underwent
CSFP measurement by lumbar puncture and
3.0-Tesla orbital magnetic resonance imaging for
different clinical reasons. After adjusting for body
mass index (BMI) and mean arterial blood pressure
(MABP), the authors developed three algorithms
for the associations between CSFP and orbital
subarachnoid space width as follows: (a) CSF-P
= 9.31 × OSASW (at 3 mm) + 0.48 × BMI + 0.14 ×
MABP – 19.94; (b) CSF-P = 16.95 × OSASW (at 9
mm) + 0.39 × BMI + 0.14 × MABP – 20.90; and
(c) CSF-P = 17.54 × OSASW (at 15 mm) + 0.47 ×
BMI + 0.13 × MABP – 21.52. Later, using the data
obtained in Xie et al´s study, Jonas and colleagues
from the same study group calculated a formula
to estimate the CSFP of a normal population.

Correspondence to:

Niro Kasahara, MD. Department of Ophthalmology,
Irmandade da Santa Casa de Misericordia de Sao Paulo,
Sao Paulo, Brazil.
E-mail: niro.kasahara@fcmsantacasasp.edu.br
Received: 23-08-2022 Accepted: 07-09-2022

Access this article online

Website: https://knepublishing.com/index.php/JOVR

DOI: 10.18502/jovr.v17i4.12344

Performing a multivariate analysis in the training
group with the lumbar CSFP measurements as
dependent variable and age, BMI and blood
pressure as independent variables revealed that
estimated CSFP was best described by the formula
of Estimated CSFP [mmHg] = 0.44 × BMI × [kg/m ]
+ 0.16 × Diastolic Blood Pressure [mmHg] – 0.18 ×
Age [Years] - 1.91.[3, 4] In fact, Xie was the coauthor
of this second paper and since the data for the
first study was used to estimate the CSFP, we
thought that paper should be cited and receive
credit.

This formula has been validated in the Brazilian
population. Kasahara et al compared the real
CSFP and the estimated one by the algorithm in a
small cohort of 39 patients scheduled for lumbar
puncture for different medical reasons.[5]Using the
Bland-Altman plot of the differences between the
two techniques against their averages, most data
points were positioned between the two limits
of agreement indicating concordance between
the two methods. The authors highlighted that
the use of the equation was not for clinical
grounds; however, it might be a suitable
surrogate method to predict CSFP in clinical
studies.[5]

This is an open access article distributed under the Creative Commons
Attribution License, which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly cited.

How to cite this article: Cruz NFS, Santos KS, Matuoka ML,
Kasahara N. Authors’ Reply. J Ophthalmic Vis Res 2022;17:603–
604.

© 2022 Cruz et al. THIS IS AN OPEN ACCESS ARTICLE DISTRIBUTED UNDER THE CREATIVE COMMONS ATTRIBUTION LICENSE | PUBLISHED BY KNOWLEDGE E 603

http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i4.12344&domain=pdf&date_stamp=2019-07-17
https://knepublishing.com/index.php/JOVR


Authors’ Reply; Cruz et al

The following quote is attributed to Sir Issac
Newton: “If I have seen further it is by standing
on the shoulders of Giants.”[6] Far from considering
ourselves as giants, we believe that Dr Cruz’s
paper is a small contribution to the emerging
large body of evidence of the role of CSFP in the
pathogeny of primary open-angle glaucoma. This
paper might inspire other researches to further
elucidate the complexity of CSFP and glaucoma.
In science, researchers have to use whatever is
available to develop their research and, in many
instances, the methods are not ideal. In this study
specifically, the measurement of CSFP by lumbar
puncture for study purposes only – with no clear
medical reason – would definitely be unethical.
Other methods for noninvasive measurement of
CSFP have been developed and although some
techniques may show great potential for specific
applications, none of these methods can fully
replace an invasive technique by lumbar puncture
and none has yet been considered the gold
standard for clinical science.[7] In the meantime,
we believe that surrogate methods, particularly the
proxy algorithm, are valid instruments to estimate
CSFP in clinical studies and no study using such
methods should be disregarded.

REFERENCES

1. Cruz NF, Santos KS, Matuoka ML, Kasahara N.
Translaminar pressure difference and ocular perfusion
pressure in glaucomatous eyes with different optic disc
sizes. J Ophthalmic Vis Res 2021;16:171–177.

2. Xie XB, Zhang XJ, Fu J, Wang H, Jonas JB, Peng X, et
al. Intracranial pressure estimation by orbital subarachnoid
space measurement. Crit Care 2013;17:R162.

3. Jonas JB, Wang N, Wang YX, You QS, Yang D, Xie X, et
al. Subfoveal choroidal thickness and cerebrospinal fluid
pressure: The Beijing Eye Study 2011. Invest Ophthalmol
Vis Sci 2014;55:1292–1298.

4. Jonas JB, Wang N, Yang D, Ritch R, Panda-Jonas S.
Facts and myths of cerebrospinal fluid pressure for the
physiology of the eye. Prog Retin Eye Res 2015;46:67–83.

5. Kasahara N, Matuoka ML, Santos KS, Cruz NF, Martins
AR, Nigro S. Validation of an equation model to predict
intracranial pressure in clinical studies. Innov Clin Neurosci
2018;15:27–29.

6. Hall AR, Tilling L, editors. The correspondence of Isaac
Newton. Volume 5. Cambridge: CUP. P. 1709–1713.

7. Price DA, Grzybowski A, Eikenberry J, Januleviciene I,
Verticchio Vercellin AC, Mathew S, et al. Review of non-
invasive intracranial pressure measurement techniques
for ophthalmology applications. Br J Ophthalmol
2020;104:887–892.

604 JOURNAL OF OPHTHALMIC AND VISION RESEARCH Volume 17, Issue 4, October-December 2022