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Vol. 11. Issue 3.
Pages 198-199 (July - September 2018)
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Vol. 11. Issue 3.
Pages 198-199 (July - September 2018)
Letter to the Editor
DOI: 10.1016/j.optom.2017.11.001
Open Access
Central corneal thickness measurement with Cirrus HD-OCT and Topcon SP-3000P
Medición del espesor corneal central con Cirrus HD-OCT y Topcon SP - 3000P
Maddalena De Bernardo
Corresponding author

Corresponding author at: Department of Medicine, Surgery and Dentistry, University of Salerno, Via Salvador Allende, 84081 Baronissi (SA), Italy.
, Francesco Antonio Salzano, Nicola Rosa
Department of Medicine and Surgery, University of Salerno, Baronissi, Salerno, Italy
Related content
J Optom. 2018;11:192-710.1016/j.optom.2016.12.004
Jorge A. Calvo-Sanz, Javier Ruiz-Alcocer, Miguel A. Sánchez-Tena
J Optom. 2018;11:19910.1016/j.optom.2017.11.002
Jorge A. Calvo-Sanz
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Dear Editor,

We read with great interest the article by Calvo-Sanz et al. comparing specular microscopy (SM) with OCT and ultrasound pachymetry (USP).1

We would like to congratulate with the authors for their excellent paper, because even if corneal thickness (CT) is not the only parameter involved in the reliability of intraocular pressure measurement,2 a precise CT measurement is very important both in establishing the corneal health3 and in evaluating the intraocular pressure.4

Their paper confirms our belief that SM measurements are in absolute thinner compared to other devices.5,6

In fact in a previous paper De Bernardo et al. found that CT obtained with this device was thinner than the measurements obtained with Pentacam, and they proposed a regression formula to make the measurements comparable.7

We agree with the authors that USP measurements depend on the exact axial placement of the probe making the reproducibility of measurements dependent on examiner expertise.8

Concerning the difference between USP and SM, the authors performed the USP after the instillation of topical anesthesia utilizing a combination of 0.1% tetracaine and 0.4% oxybuprocaine.

Theoretically this could have given some differences, because it is true that in a previous published paper it has been demonstrated no influence on CT and volume measurements with the instillation of oxybuprocaine eye drops,9 but tetracaine eye drops have been described to cause corneal thickening.10

So in conclusion we would like to suggest that for future works concerning the comparison of different devices the use of oxybuprocaine, better if preservative free, instead of tetracaine should be advisable.



J.A. Calvo-Sanz, J. Ruiz-Alcocer, M.A. Sánchez-Tena.
Accuracy of Cirrus HD-OCT and Topcon SP-3000P for measuring central corneal thickness.
N. Rosa, M. Lanza, M. Borrelli, A. Palladino, M.G. Di Gregorio, L. Politano.
Intraocular pressure and corneal biomechanical properties in patients with myotonic dystrophy.
Ophthalmology, 116 (2009), pp. 231-234
N. Rosa, M. Lanza, M. Borrelli, et al.
Corneal thickness and endothelial cell characteristics in patients with myotonic dystrophy.
Ophthalmology, 117 (2010), pp. 223-225
M. Lanza, M. Borrelli, M. De Bernardo, M.L. Filosa, N. Rosa.
Corneal parameters and difference between Goldmann applanation tonometry and dynamic contour tonometry in normal eyes.
J Glaucoma, 17 (2008), pp. 460-464
M. De Bernardo, N. Rosa.
Comparison of specular microscopy and ultrasound pachymetry before and after cataract surgery.
Graefes Arch Clin Exp Ophthalmol, 255 (2017), pp. 837-838
M. De Bernardo, N. Rosa.
Central corneal thickness after cross-linking using high-definition optical coherence tomography ultrasound, and dual Scheimpflug tomography: a comparative study over one year.
Am J Ophthalmol, 176 (2017), pp. 254
M. De Bernardo, M. Borrelli, M. Mariniello, M. Lanza, N. Rosa.
Pentacam vs SP3000P specular microscopy in measuring corneal thickness.
Cont Lens Anterior Eye, 38 (2015), pp. 21-27
N. Rosa, M. De Bernardo.
Central corneal thickness determination in corneal edema.
Graefes Arch Clin Exp Ophthalmol, 255 (2017), pp. 1251-1252
N. Rosa, M. De Bernardo, M. Borrelli, M.L. Filosa, M. Lanza.
Effect of oxybuprocaine eye drops on corneal volume and thickness measurements.
Optom Vis Sci, 88 (2011), pp. 640-644
U.L. Osuagwu, K.C. Ogbuehi.
Evaluation of the comparative effect of tetracaine on central corneal thickness measured by a contact and noncontact pachymeter.
J Ocul Pharmacol Ther, 29 (2013), pp. 68-74
Copyright © 2018. Spanish General Council of Optometry
Journal of Optometry

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