Which tonometry in eyes with keratoconus?

Aims: To compare intraocular pressure (IOP) measurements obtained with Goldmann applanation tonometery (GAT), dynamic contour tonometry (DCT), tonopen (TP), and ocular response analyzer (ORA), and to determine the influence of Amsler grade and central corneal thickness (CCT) on the IOP readings in eyes with keratoconus that are classified into four groups according to the Amsler-Krumeich classification.
Methods: All eyes with keratoconus were separated into four groups using Amsler-Krumeich classification for keratoconus. IOP was measured in 202 eyes of 202 patients with keratoconus using GAT, DCT, TP, and ORA.
Results: The IOP differences revealed no significant difference among the Amsler degree in the DCT and corneal-compensated IOP (IOPcc) measurements (P>0.05 for all). There was no statistically significant difference in terms of IOP differences between GAT and IOPcc (P>0.05), TP and Goldmann-correlated measure of IOP (IOPg; P>0.05) in the Amsler I, while the IOP measurements revealed significant difference among the measurements of the four different tonometers in the Amsler II, Amsler III, and Amsler IV (P<0.05 for all).
Conclusions: There was no significant association between DCT IOP or IOPcc and CCT in eyes with keratoconus; no statistically significant difference was found between keratoconus stages and the control group in terms of the IOP analyzed with these two techniques. These two techniques may be the most stable in the measurement of IOP in different keratoconus stages. However, no IOP technique can be used interchangeably with other techniques in the follow-up of keratoconus patients.