Clinical Usefulness of Pachymetry in Known Glaucoma Patients

Abstract

Abstract: : Purpose: It has been shown that central corneal thickness (CCT) is of value in patients with ocular hypertension. We investigated whether CCT was also of value in patients with a known history of glaucoma. Normal tension glaucoma patients were excluded. Methods:A retrospective study was performed on 135 patients (237 eyes) with a diagnosis of glaucoma. Intraocular pressure (IOP) was obtained by Goldmann applanation tonometry and CCT was obtained using ultrasonic pachymetry. Based on mean CCT, IOP was adjusted using correction values modified from the work of Doughty and Zamen¹. The adjusted IOP was then compared to the patient’s target pressure. A change in clinical treatment, including the addition or removal of anti–glaucoma medications, laser treatment, or surgical treatment, was noted in certain patients for IOP corrections of 1 mmHg or greater. Results:Overall, 21.5% of glaucoma patients (29 out of 135) or 13.5% of the treated eyes (32 out of 237) had an alteration in their treatment secondary to their CCT adjusted IOP. 15 patients (18 eyes) avoided additional therapy that they otherwise would have had if pachymetry had not been done; group mean CCT 598 ± 29.5 µm; group mean IOP correction –2.3 ± 1. 14 patients (14 eyes) required additional treatment secondary to their adjusted IOP. 7 had medication added, 5 underwent laser trabeculoplasty, and 2 underwent glaucoma filtration surgery; group mean CCT 499 ± 19.6µm; group mean IOP correction +2.6 ± 1. Conclusions: Performing pachymetry in known glaucoma patients may alter their management, either by allowing patients to avoid unnecessary treatment or by requiring additional treatment. In particular, this has clinical significance in the management of patients whose target pressures were set based on the degree of disc and field damage.² Therefore, pachymetry should be performed on all glaucoma patients with a history of elevated IOP to determine the relationship between the CCT–adjusted IOP and their target pressure.

Keywords: intraocular pressure