Goldmann Applanation Tonometer versus Noncontact Autotonometer In Measurement Of Intraocular Pressure Ineyes With Myopia – A Descriptive Observational Study

Abstract

Purpose of the study: ABSTRACT To find out the specificity and sensitivity of non-contact autotonometer in detecting intraocular pressure in eyes with myopia and also to compare the positive and negative predictive value of non-contact autotonometer and Goldmann applanation tonometer. Methods: A total of 236 eyes of 118 patients having myopia of more than 2 D and age between 18 to 40 years were studied. Each eye had undergone subjective refraction testing, IOP measurement with non-contact autotonometer and Goldmann applanation tonometer and then the measurement of corneal curvature, axial length and anterior chamber depth. Funduscopic examination was carried out thoroughly by indirect ophthalmoscopy with +20 D lens. Results: The sensitivity of non-contact autotonometer in detecting IOP > 21 mm Hg was found to be 84.21%. The specificity, positive and negative predictive values were 95.96%, 80% and 96.94% respectively. The correlation coefficient between the two instruments was found to be 0.880 (p< 0.0001) which was highly significant. Positive correlation was found between degree of myopia and axial length with IOP whereas a negative correlation was found between the corneal curvature and anterior chamber depth with IOP as measured with both non-contact autotonometer and Goldmann applanation tonometer. X Conclusion: Eventhough the Goldmann applanation tonometer is considered to be the gold standard for measurement of IOP, non-contact autotonometer with its reliable, practical, associated low cross infection risk, with high sensitivity and specificity, comparable performance with Goldmann applanation tonometer and a good patient compliance, can be used to screen the myopes who are likely to be associated with raised IOP and primary open angle glaucoma. Degree of myopia and axial length were seen to have an influence on IOP with a positive correlation, while a negative correlation of corneal curvature and anterior chamber depth with IOP as measured with non-contact autotonometer and Goldmann applanation tonometer was observed. Hence it was concluded from the present study that irrespective of degree of myopia, axial length, corneal curvature and anterior chamber depth, non-contact autotonometer can provide a reliable and an accurate measurement of IOP when compared to the standard Goldmann applanation tonometer.