Diagnostic Availability of Ocular Response Analyzer in Korean Patients with Normal Tension Glaucoma

ABSTRACT

PURPOSE: To compare the parameters measured with the ocular response analyzer (ORA; Reichert Inc., Depew, NY, USA) between normal control subjects and patients with normal tension glaucoma (NTG) and to investigate clinical usefulness of ORA. METHODS: Intraocular pressure (IOP) and central corneal thickness (CCT) were measured using the Goldmann applanation tonometer (GAT) in 100 eyes of 100 normal subjects and 100 eyes of 100 NTG patients. Four types of ORA parameters, corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann-correlated IOP (IOPg), and corneal-compensated IOP (IOPcc) were also measured. RESULTS: The mean CH values were 11.2 mm Hg and 10.3 mm Hg and the mean CRF values were 10.8 mm Hg and 9.9 mm Hg in the normal subjects group and the NTG group, respectively. Mean CH and CRF were significantly lower in NTG patients (p < 0.001) and the IOPcc were higher than normal subjects (p = 0.004). IOPg was in agreement with the GAT IOP (ICC = 0.811) and IOPcc was not correlated with CCT. The cut-off value of 'IOPcc - IOPg' as the diagnostic standard parameter was -0.05 mm Hg (sensitivity; 76%, specificity; 55%). CONCLUSIONS: IOPg measurements were similar to GAT IOP, and other ORA parameters (CH, CRF, IOPcc) were significantly different between normal subjects and NTG patients. Consequently, the difference of IOPcc and IOPg could be a useful parameter in NTG diagnosis.