Measuring intraocular pressure-adjustments for corneal thickness and new technologies

Abstract

Central corneal thickness has become an important biometric factor and is an essential part of the evaluation of glaucoma. Goldmann applanation tonometry is the most widely used method of measuring intraocular pressure, but it is well known that corneal parameters affect the accuracy of this instrument. Intraocular pressure reduction is currently the only treatment available for decreasing the risk of glaucoma progression, so it is important to have an accurate reading of the true intraocular pressure. New tonometers such as the dynamic contour tonometer and the Proview tonometer do not appear to be influenced by central corneal thickness. The ocular response analyzer provides a new measure of corneal biomechanics called corneal hysteresis. Rebound tonometry has been used in animal models of glaucoma, but has recently been compared to Goldmann applanation tonometry in humans. All of these technologies are presented in this review and the influence of corneal thickness on their accuracy is examined. Confronted with the expanding evidence that central corneal thickness is an important ocular parameter that should be measured in clinical practice, eye-care professionals understandably wonder how to best obtain the measurements and what to do with the information. There is wide disagreement among investigators as to if there is an adequately validated 'correction algorithm'; without a validated algorithm, the argument goes, clinicians cannot use the data. These newer technologies may allow clinicians to be able to accurately determine the true intraocular pressure without having to rely on a correction algorithm.