Pascal dynamic contour tonometry a ‘promising’ alternative to applanation

NEW ORLEANS — A new device may overcome some of the limitations of Goldmann applanation tonometry in measuring IOP, according to one clinician.

Leon W. Herndon Jr., MD, said that the new technology, Pascal dynamic contour tonometry, is a “promising” alternative to Goldmann tonometry, which he said is “flawed.” Dr. Herndon told attendees here at glaucoma subspecialty day at the American Academy of Ophthalmology that although Goldmann tonometry is the most widely used method of measuring IOP, several factors can affect its accuracy, including variations in corneal thickness and changes in the cornea after refractive surgery.

The Pascal dynamic contour tonometer (Ziemer Ophthalmic Systems) is a contact tonometer with a tip that fits into a standard Goldmann tonometer stand, Dr. Herndon said. It reads IOP using an electronic pressure sensor placed in the center of the cornea.

Dr. Herndon described a study in 62 patients who underwent unilateral LASIK. IOP was measured with both Goldmann and dynamic contour tonometry pre- and postoperatively. The researchers found that the mean Goldmann tonometry reading decreased by 3 mm Hg postoperatively. There was no significant change in IOP from preop to postop as measured by dynamic contour tonometry, he said.

In another study, IOP was measured using both methods in 118 healthy eyes before and 1 and 4 weeks after LASIK. Dr. Herndon said that from preop to 1 week postop there was a mean drop of 4.9 mm Hg in the Goldmann tonometry reading, and preop to 4 weeks postop the drop was 5.4 mm Hg. There was no significant change in IOP at either follow-up as measured by dynamic contour tonometry, he said.