<prompt> For tonometry is :4 xylocaine3 xylocaine2 xylocaine1 xylocaine  <response>: Tonometry is the method of measuring intraocular pressure using calibrated instruments. The normal range is 10 to 21 mm Hg.Schiotz tonometry, a drop of surface anaesthetic solution like 4xylocaine is used. Ref :Greenberg R.D., Daniel K.J. 2011. Chapter 31. Eye Emergencies. In R.L. Humphries, C. Stone Eds, CURRENT Diagnosis Treatment Emergency Medicine, 7e. 