Evaluation of Corvis ST tonometer with the updated software in glaucoma practice

Ioannis Halkiadakis; Vasilios Tzimis; Alexandros Gryparis; Ioannis Markopoulos; Vasiliki Konstadinidou; Elias Zintzaras; Michalis Tzakos

doi:10.18240/ijo.2022.03.11

Evaluation of Corvis ST tonometer with the updated software in glaucoma practice

Int J Ophthalmol. 2022 Mar 18;15(3):438-445. doi: 10.18240/ijo.2022.03.11. eCollection 2022.

Authors

Ioannis Halkiadakis¹, Vasilios Tzimis¹, Alexandros Gryparis², Ioannis Markopoulos¹, Vasiliki Konstadinidou¹, Elias Zintzaras³, Michalis Tzakos¹

Affiliations

¹ Ophthalmiatrion Athinon, Athens Eye Hospital, El Venizelou 26 & Sina 2, Athens 10672, Greece.
² Unit of Endocrinology, Diabetes Mellitus and Metabolism, Aretaieion Hospital, National and Kapodistrian University of Athens, School of Medicine, Athens 11528, Greece.
³ Department of Biomathematics, University of Thessaly School of Medicine Larissa, Greece and Institute for Clinical Research and Health Policy Studies Tufts University School of Medicine, Boston, MA 02111, USA.

Abstract

Aim: To evaluate the agreement of biomechanically corrected intraocular pressure (b-IOP) and central corneal thickness (CCT) measurements obtained with the updated Corvis ST tonometer versus Goldmann applanation tonometry (GAT) and optical-based corneal pachymetry (OB-CCT) in controls, patients with ocular hypertension (OHT) and primary open angle glaucoma (POAG). Additionally, we examined the differences in corneal deformation parameters provided by the updated Corvis ST among the three groups.

Methods: For each participant, GAT IOP, OB-CCT and measurements with a Corvis ST with updated software were obtained. Bland-Altman analysis was used to assess the agreement between the two measurement methods.

Results: A consecutive series of 80 eyes from 80 participants (30 with POAG, 25 with OHT and 25 normal controls) were included in this prospective study. The mean GAT IOP of all eyes was 17.2±3.6 mm Hg, and the mean b-IOP was 15.9±3.7 mm Hg (Spearman's rho=0.767, P<0.001). The 95% limits of agreement (LoAs) ranged from -3.1 mm Hg to 5.5 mm Hg for GAT IOP and b-IOP. b-IOP was not correlated with OB-CCT (Spearman's rho=-0.13 P=0.917). Meanwhile there was a weak positive corelation between OB-CCT and GAT IOP-b-IOP difference (Spearman's rho=0.378, P=0.001). The mean OB-CCT was 549.5±36.4 µm, and the Corvis-CCT was 556.1±41.5 µm (Spearman's rho=0.900, P<0.001). No statistically significant difference in the new indices provided by the updated Corvis ST was detected among the three groups. Compared with control eyes, POAG eyes had a significantly reduced applanation time 2 after adjusting for OB-CCT and GAT IOP (P=0.048).

Conclusion: Corvis b-IOP and CCT correlate well with GAT IOP and OB-CCT. b-IOP is not affected by CCT, which might be an advantage, especially in thick or thin corneas. Corvis ST yields shorter applanation time 2 measurements in patients with POAG, which might reflect altered corneal viscoelasticity.

Keywords: corneal biomechanics; glaucoma; intraocular pressure; ocular hypertension; tonometry.

International Journal of Ophthalmology Press.