Glaucoma Screening With a New Non-Contact Air Impulse Tonometer

1. Glaucoma Screening With a New Non-Contact Air Impulse Tonometer Pandelis A. Papadopoulos,1,2, Dimitrios P. Bessinis3, Alexandros A. Papadopoulos1, KonstantinosKakoulidis2and Andrej Cernak2 • Ophthalmo-Check Eye Center, Athens, Greece • Department of Ophthalmology, Slovak Medical University, Bratislava, Slovakia • Department of Ophthalmology, Evaggelismos General Hospital, Athens, Greece • the authors declare that they have no financial interest in the products mentioned in the study

2. RATIONALE Corvis ST is a Non-Contact Tonometer which allows the measurement of IOP and CCT with a high speed Scheimpflug camera (4300 fps) and records the movement reaction to the cornea to an air impulse. Apart from corneal biomechanical properties, Corvis ST allows the assesemnt of corrected IOP with various formulas. The purpose of this study was to evaluate the accuracy of data provided by Corvis ST (CST), a newly developed tonometer with features of visualization and measurement of the corneal deformation response to an air impulse, for intraocular pressure (IOP) compared to Goldmanntonometer (GAT) and a non-contact tonometer (NCT) as well as central corneal thickness (CCT) compared to U/S pachymetry and Pentacam. MATERIALS AND METHODS Sixty Seven eyes of 34 patients were examined using the three different methods for IOP and Central Corneal Thickness (CCT). Statistical analysis was performed with SPSS software for Windows using Bland-Altman plot.

3. GAT NCT CST U/S pachymetry Pentacam HR

4. NCT measured higher IOP compared to CST (0,39 mmHg) and GAT (0,44mmHg) Nevertheless, the deviation of the measurements was lower for CST compared to GAT (95% limits of agreement ±4,86)

5. CCT was found higher when using CST compared to standard U/S pachymetry (9.21667 um) and Pentacam (2.675 um) CST readings for CCT were closer to Pentacam compared to U/S pachymetry.

6. CONCLUSIONS • CST offers an alternative method for obtaining IOP and CCT readings. Its measurements are closer to those of GAT when compared to another air tonometer. The readings of CST appear to be higher than those of U/S pachymetry for CCT but closer to Pentacam. It is safe to conclude that Corvis ST is an alternative method for providing data adequate for glaucoma screening. Nevertheless, its significance for glaucoma monitoring and keratoconus screening is still under evaluation. REFERENCES Agrawal A, Pratap VP, Pal VK, Suman S (A comparison between rebound and Goldmann'stonometers in screening of patients for glaucoma. Nepal J Ophthalmol 4:201-202.2012). Baneros-Rojas P, Martinez de la Casa JM, Arribas-Pardo P, Berrozpe-Villabona C, Toro-Utrera P, Garcia-Feijoo J (Comparison between Goldmann, Icare Pro and Corvis ST tonometry. Arch Soc EspOftalmol 89:260-264.2014). de Vries MM, Stoutenbeek R, Muskens RP, Jansonius NM (Glaucoma screening during regular optician visits: the feasibility and specificity of screening in real life. ActaOphthalmol 90:115-121.2012). Gower EW, Whiteside-de Vos J, Cassard SD, Shekhawat NS, Friedman DS (The medicare glaucoma screening benefit: a critical program that misses its target. Am J Ophthalmol 156:211-212 e212.2013). Hong J, Xu J, Wei A, Deng SX, Cui X, Yu X, Sun X (A new tonometer--the Corvis ST tonometer: clinical comparison with noncontact and Goldmannapplanationtonometers. Investigative ophthalmology & visual science 54:659-665.2013). McManus JR, Netland PA (Screening for glaucoma: rationale and strategies. CurrOpinOphthalmol 24:144-149.2013). Patel HY, Richards AJ, De Karolyi B, Best SJ, Danesh-Meyer HV, Vincent AL (Screening glaucoma genes in adult glaucoma suggests a multiallelic contribution of CYP1B1 to open-angle glaucoma phenotypes. Clin Experiment Ophthalmol 40:e208-217.2012). Valbon BF, Ambrosio R, Jr., Fontes BM, Luz A, Roberts CJ, Alves MR (Ocular Biomechanical Metrics by CorVis ST in Healthy Brazilian Patients. J Refract Surg 30:468-473.2014).