Journal of Optometry Journal of Optometry
J Optom 2018;11:130-1 - Vol. 11 Num.2 DOI: 10.1016/j.optom.2017.10.001
Letter to the Editor
Evaluation of Goldmann applanation tonometry, rebound tonometry and dynamic contour tonometry in keratoconus
Evaluación de la tonometría por aplanación de Goldmann, la tonometría de rebote y la tonometría de contorno dinámico en el queratocono
Maddalena De Bernardo, , Nicola Rosa
Department of Medicine and Surgery, University of Salerno, Baronissi, Salerno, Italy
Dear Editor,

We read with great interest the article by Özcura et al.,1 concerning the evaluation of Goldmann applanation tonometry (GAT), rebound tonometry (RT) and dynamic contour tonometry (DCT) in patients affected by keratoconus, suggesting that DCT may be the most appropriate tonometer to use in keratoconus for the measurements of intraocular pressure (IOP), because DCT does not appear to be dependent upon corneal thickness (CCT) and radius (CR).

This paper confirms previous finding in normal patients, as Lanza et al. found that DCT showed higher values of IOP, mainly related to CCT and volume, concluding that, if in the future DCT should be considered the gold standard, higher values of IOP could still be considered normal.2

In our opinion, in cases of keratoconus the difference between DCT and GAT could also be related to the corneal biomechanical changes, such as corneal hysteresis (CH) and corneal resistance factor (CRF). The same happens in corneas that underwent refractive surgery, where the changes in corneal thickness and radius make GAT and IOL power calculation unreliable.3–7

Moreover in these patients a significant decrease of CH and CRF immediately after myopic PRK that remains stable over the follow-up has been described, compared to normal eyes, in which these parameters have been shown to be related to the corneal shape and thickness. So these parameters could in addition influence the unreliability of GAT, making the DCT potentially better.8,9

A similar behavior therefore could be present in patients affected by keratoconus, where CH and CRF changes10 too could influence the differences between GAT and DCT, increasing or decreasing such differences.

Sources of public and private financial support

None.

Financial disclosure

None.

References
1
F. Özcura,N. Yıldırım,E. Tambova,A. Sahin
Evaluation of Goldmann applanation tonometry, rebound tonometry and dynamic contour tonometry in keratoconus
2
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
3
M. De Bernardo,L. Capasso,L. Caliendo,Y. Vosa,N. Rosa
Intraocular pressure evaluation after myopic refractive surgery: a comparison of methods in 121 eyes
Semin Ophthalmol, 31 (2016), pp. 233-242 http://dx.doi.org/10.3109/08820538.2014.962156
4
M. De Bernardo,N. Rosa
Intraocular pressure after refractive surgery
5
M. De Bernardo,N. Rosa
Correlation between dynamic contour tonometry, uncorrected and corrected Goldmann applanation tonometry, and stage of glaucoma
JAMA Ophthalmol, 11 (2018), pp. 130-131
6
N. Rosa,L. Capasso,M. Lanza,M. Borrelli
Clinical results of a corneal radius correcting factor in calculating intraocular lens power after corneal refractive surgery
J Refract Surg, 25 (2009), pp. 599-603
7
N. Rosa,M. De Bernardo,M. Borrelli,M. Lanza
New factor to improve reliability of the clinical history method for intraocular lens power calculation after refractive surgery
J Cataract Refract Surg, 36 (2010), pp. 2123-2128 http://dx.doi.org/10.1016/j.jcrs.2010.07.017
8
N. Rosa,M. Lanza,M. De Bernardo,G. Signoriello,P. Chiodini
Relationship between corneal hysteresis and corneal resistance factor with other ocular parameters
Semin Ophthalmol, 30 (2015), pp. 335-339 http://dx.doi.org/10.3109/08820538.2013.874479
9
N. Rosa,M. De Bernardo,S. Iaccarino,M. Lanza
Corneal biomechanical changes after myopic photorefractive keratectomy
Semin Ophthalmol, 30 (2015), pp. 328-334 http://dx.doi.org/10.3109/08820538.2013.874478
10
M. De Bernardo,L. Capasso,M. Lanza
Long-term results of corneal collagen crosslinking for progressive keratoconus
Corresponding author at: Department of Medicine and Surgery, University of Salerno, Via Salvador Allende, 84081 Baronissi (SA), Italy. (Maddalena De Bernardo mdebernardo@unisa.it)
Copyright © 2017. Spanish General Council of Optometry
J Optom 2018;11:130-1 - Vol. 11 Num.2 DOI: 10.1016/j.optom.2017.10.001