A Low Ratio between Central Corneal Thickness and Mid-peripheral or Peripheral Corneal Thickness in Normal Tension Glaucoma

Sang Woo Park

Purpose: To investigate the structural differences in the cornea between normal tension glaucoma (NTG) and primary open angle glaucoma (POAG).

Methods: Central corneal thickness (CCT), mid-peripheral central corneal thickness (MPCT) and peripheral corneal thickness (PCT) were calculated by anterior segment optical coherence tomography (AS-OCT) in the NTG, POAG and controls. The ratio between the central corneal thickness and midperipheral or peripheral corneal thickness was compared among the three groups. The correlation between CCT and MPCT, as well as CCT and PCT was analyzed in each group.

Results: The CCT was thinner in patients with NTG than in patients with POAG (p=0.004) and the controls (p=0.004). The ratio of the CCT/MPCT for the NTG group was significantly lower than in the POAG (p=0.004) and controls (p=0.001). The ratio of the CCT/PCT in the NTG group was significantly lower than the POAG (p=0.031) and controls (p=0.029). A significant correlation was found between the CCT and MPCT in patients with NTG (r=0.695, p=0.006), POAG (r=0.886, p<0.001) and the controls (r=0.829, p<0.001). Comparison between the CCT and PCT, showed a significant correlation in patients with NTG (r=0.821, p<0.001); however, there was no significant correlation in the POAG (r=0.441, p=0.151) and the controls (r=0.353, p=0.051).

Conclusions: The findings of this study demonstrate the different structure of the cornea associated with NTG, and might aid in the explanation of the pathogenesis of glaucomatous optic nerve changes in patients with NTG.