International Journal of Science and Research (IJSR) ISSN (Online): 2319-7064 Index Copernicus Value (2015): 78.96 | Impact Factor (2015): 6.391 Volume 6 Issue 5, May 2017 www.ijsr.net Licensed Under Creative Commons Attribution CC BY A Comparative Study of Intraocular Pressure Measurement Using Tonopen and Goldmann Applanation Tonometer Dr. Rajesh R Nayak 1 , Dr. Pooja Kandula 2 , Dr. Bhavini Johri 3 , Dr. Shobha G Pai 4 , Dr. Sumana J Kamath 5 1 Associate Professor, Kasturba Medical College, Mangalore, Manipal University 2 Postgraduate, Kasturba Medical College, Mangalore, Manipal University 3 Undergraduate, Kasturba Medical College, Mangalore, Manipal University 4 Head of the Department, Kasturba Medical College, Mangalore, Manipal University 5 Professor, Kasturba Medical College, Mangalore, Manipal University Abstract: Background : Glaucoma is the world's leading cause of preventable irreversible blindness. The most important risk factor of glaucoma is increase in the intraocular pressure.Hence, timely screening by accurate IOP measurements is of utmost importance. In recent years, Tonopen has emerged as an alternative to Goldmann applanation tonometer which is the ‘gold standard’ for IOP measurement because of its various advantages. Since its reliability has not yet been confirmed, this study aims to assess the accuracy of the Tonopen in measuring the IOP as compared to the Goldmann applanation tonometer. Objective : To determine whether Tonopen is accurate and reliable in measuring the intraocular pressure as compared to Goldmann applanation tonometer. Methodology : In this prospective cross-sectional study, 113 patients above 40 years coming for routine eye check-up and who were diagnosed earlier as glaucoma patients their IOP was measured. The Tonopen was used first followed by the Goldmann applanation tonometer. Collected data was analyzed using SPSS version 17.0. The results were expressed in terms of sensitivity, specificity, positive and negative predictive value and accuracy rate. Institutional Ethics Committee clearance was obtained prior to commencement of study. Results : For the right eye, the sensitivity of the Tonopen in detecting glaucoma was 60% and the specificity was 94.44%. The positive predictive value and the negative predictive value were 33.33%and 98.08% respectively. Percentage of false-negatives obtained were 40% and percentage of false-positives obtained were 5.55%. Accuracy rate of the Tonopen was 92.92%. For the left eye, sensitivity was 75% and specificity was 96.33%. The Positive predictive value and negative predictive value were42.86% and 99.06% respectively. Percentage of false-negatives obtained were 25% and percentage of false-positives were 3.67%. Accuracy rate of the Tonopen was 95.57%. Area under the Receiver Operating Characteristic curve was 0.887 with a standard error of 0.085 in case of the right eye. For the left eye, the area under the curve was 0.972 with a standard error of 0.027. Conclusion : According to this study, the Tonopen is an accurate and reliable indicator of Intraocular pressure. Keywords: Goldmann applanation, Tonopen, glaucoma 1. Introduction Intraocular pressure is determined by the balance between the rate of aqueous production and its outflow which is in turn related to factors that include the resistance encountered in the trabeculum and the level of episcleral venous pressure. [1] An IOP between 10 and 21 mm Hg is considered to be statistically normal. [2] .According to the statistics in 2010, Glaucoma is estimated to be affecting 60.5 million persons and responsible for vision loss among 8.4 million. The silver lining in the cloud is that the rate of visual deterioration can be reduced by lowering of intraocular pressure. Hence, timely screening for this disease can save many patients from turning blind. [3] As a result, accurate IOP measurements are of utmost importance and any discrepancies could lead to delay in the detection and treatment of this disease. [4] For uncooperative patients or those who have irregular corneas, Tonopen may be considered as an alternative over Goldmann applanation tonometer. The Tonopen is an automatic microprocessor controlled tonometer which is compact and portable. Also, it operates independent of patient position and is easy to calibrate and operate. Other advantages are that its tip has a disposable cover which helps to eliminate contamination risks and user bias is effectively minimized by the digital readout. [4, 5] There is no substantial proof yet for the Tonopen being a reliable indicator of intraocular pressure, however certain studies suggest that Tonopen measures IOP accurately which could help overcome the limitations of the Goldmanntonometer [4] . Hence, the need of the hour is to conduct further investigations and carry out more research to arrive at a conclusion. Depending on the outcome, use of the Tonopen can be encouraged or discouraged in clinical practice. 2. Objective To determine whether Tonopen is accurate and reliable in measuring the intraocular pressure as compared to Goldmann applanation tonometer. Paper ID: ART20173327 665