Influence of Central Corneal Thickness on Diagnosis of Glaucoma

ABSTRACT

PURPOSE: To determine the effect of central corneal thickness (CCT) on the measurement of intraocular pressure (IOP) and diagnosis of glaucoma on the resultant reclassification of patients as having primary open-angle glaucoma (POAG), normal tension glaucoma (NTG), or ocular hypertension (OHT). METHODS: Intraocular pressure (Goldmann applanation tonometry) and visual field test (Humphrey 24-2) were measured in 22 eyes of 23 patients with OHT, 20 eyes of 20 patients with POAG, 31 eyes of 31 patients with NTG, 27 eyes of 27 control subjects. CCT was measured and used to obtain a corrected value for the IOP and to reclassify the type of glaucoma. RESULTS: There was no significant difference in CCT between controls and patients with POAG, but the CCT in the group with NTG was significantly lower than that in the control group (p=0.012), and the CCT in the group with OHT was significantly higher than in controls (p=0.002). Correcting IOP for corneal thickness, 22.58% of patients with NTG could be reclassified as having POAG, and 56.52% of the patients with OHT as normal. CONCLUSIONS: Underestimation of the IOP in patients with POAG who have thin cornea may lead to a misdiagnosis of NTG, while overestimation of the IOP in normal subjects who have thick cornea may lead to a misdiagnosis of OHT. We suggest that CCT must be considered in diagnosis of glaucoma.