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Bulgarian Review of Ophthalmology

Comparative analysis of intraocular pressure measured with non-contact air tonometry (Tonopachy NT-530P) and non-contact tonometer with detection of corneal biomechanical response (OCULUS Corvis ST)

Evgeni Neshkinski



The measurement of intraocular pressure (IOP) is one of the standard tests in performing an ophthalmology examination. These values are among the parameters used to diagnose and monitor one of the commonly seen socially significant diseases—glaucoma. Therefore, accurate measurement with high recurrence and low error rate is crucial for the correct diagnosis, monitoring, and treatment of these diseases.


The aim of this article is to make a comparative analysis between the results obtained by measuring intraocular pressure, using a popular method with Tonopachy NT 530P non-contact air tonometry and innovative Corvis ST non-contact tonometer with detection of corneal biomechanical response.

Materials and Methods:

The current study presents results from 20 patients (40 eyes), including glaucoma patients (n = 7) and а control group (n = 13). The intraocular pressure and optical pachymetry of all participants were measured with Tonopachy NT-530P non-contact air tonometer and OCULUS Corvis ST non-contact air tonometer. 


The mean values of IOP with Tonopachy NT-530P are equal to  17.97 +/- 4.04 mmHg mmHg, and with Corvis ST—17.43 +/- 4.86 mmHg. The obtained results show that the uncorrected IOP of the right eye (TOD) difference between the two devices is equal to 0.515 mmHg, with standard deviation SD = 1.5118, p < 0.01. The average difference in the measurement of uncorrected IOP of the left eye (TOS) is equal to 1.9 mmHg, SD = 2.7237, p < 0.01.  For the corrected TOD, the difference in results is 0.545 mmHg, SD = 1.98162 mmHg, p < 0.01, and for the corrected TOS, it is 1.78 mmHg, SD = 2.722668 mmHg, p < 0.01. The results show that in the study group there is a tendency for higher values obtained with the Tonopachy NT530P tonometer compared to Corvis ST. The difference in results is exacerbated by an increase in IOP in patients with abnormally high IOP.


The non-contact tonometer with detection of biomechanical response of the cornea is another method that helps the modern ophthalmologist. Thanks to the detailed analysis of the cornea, which is done during tonometry, the method could be used for early detection and more effective monitoring and treatment of glaucoma.


non-contact tonometer, Corvis ST, corneal biomechanics, innovation, glaucoma

Full Text


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About The Author

Evgeni Neshkinski
Medical University of Varna

Department of Ophthalmology and Visual Sciences, Faculty of Medicine;

Specialized Eye Hospital, Varna