Dynamic contour tonometry: principle and use

Abstract

Interindividual variability of central corneal thickness has been found to be a source of error for conventional Goldmann applanation tonometry. The dynamic contour tonometer represents a potentially new technology for non-invasive and direct intraocular pressure (IOP) measurement, and has been proposed to accurately measure the true IOP irrespective of the corneal thickness. It is based on the principle that when the tip of the device exactly matches the contour of the cornea, the pressure measured by a transducer placed on its tip is an accurate indicator of the true IOP. This device is also capable of measuring the ocular pulse amplitude, a variable that has controversial significance in the diagnosis and management of glaucoma. Even though this technique seems to be very promising, further studies are required to conclusively determine the effectiveness of the dynamic contour tonometer in patients having an abnormal or irregular corneal contour.

Ocular pulse amplitude as a diagnostic adjunct in giant cell arteritis

“…integration into the diagnostic work-up is unproblematic in most cases. 20,21 Interestingly, in a population-based study on a series of biopsy-proven GCA, only 1 (0.4%) out of 240 patients had an ESR lower than 40 mm/1st hour, and the median ESR value was 93 mm/1st hour. 22 Also, in that series, 17 (48.8%) of the 240 biopsy-proven GCA patients had platelet counts higher than greater than 400 000/mm 3 .…”

Correlation between diurnal variation of intraocular pressure, ocular pulse amplitude and corneal structural properties

“…However, GAT can be influenced by factors related to the corneal properties, such as corneal curvature and central corneal thickness (CCT) (3) . These findings have prompted the development of new instruments to adjust IOP measurements according to these properties, such as the dynamic contour tonometry (DCT) and the cornealcompensated ocular response analyzer intraocular pressure (ORAcc) (4)(5)(6) . The DCT is a nonapplanation contact tonometer supposed to measure IOP independently of CCT and corneal curvature (4) .…”

“…These findings have prompted the development of new instruments to adjust IOP measurements according to these properties, such as the dynamic contour tonometry (DCT) and the cornealcompensated ocular response analyzer intraocular pressure (ORAcc) (4)(5)(6) . The DCT is a nonapplanation contact tonometer supposed to measure IOP independently of CCT and corneal curvature (4) . The DCT also provides the ocular pulse amplitude (OPA), which has been pointed as an indirect indicator of choroidal perfusion and reflection of ocular blood flow corresponding to heart pulse as a function of time (5) .…”

Clinical evaluation of multiparameter correction equations for Goldmann applanation tonometry

“…While it has been claimed that new contact tonometers, in particular the DCT can provide IOP estimates that are less affected than GAT by the effects of corneal stiffness, 34,35 GAT still maintains its worldwide position as the reference standard in tonometry 5 and the most commonly used device in clinical practice. The results of this study, which identify the suitability of two multiparameter correction equations in reducing the stiffnessrelated errors in IOP measurement, should therefore be considered a step in the right direction to potentially lead to better clinical management of glaucoma.…”