Differences in corneal parameters between normal tension glaucoma and primary open-angle glaucoma

The purpose of this study was to identify the differences in corneal parameters between medically treated normal tension glaucoma (NTG) and primary open-angle glaucoma (POAG) subjects. This cross-sectional study from September 2011 to September 2012 included consecutive subjects with POAG and NTG who were receiving topical anti-glaucoma medications at the time of the study. Subjects were excluded if they had pre-existing corneal pathology or scars and previous glaucoma lasers. The following parameters were compared between the NTG and POAG groups: endothelial cell count, central corneal thickness (CCT), spherical equivalent, presenting and current intraocular pressure (IOP), number and type of anti-glaucoma medication, retinal nerve fibre layer thickness, visual field index, visual acuity, and phakic status. Only the right eye was used for statistical analysis. The right eye of the 30 NTG and 28 POAG subjects had comparable baseline characteristics, post-treatment IOP, and glaucoma severity. The endothelial cell count was significantly lower in the NTG versus the POAG group (2,380.0 ± 315.4 vs. 2,530.0 ± 320.4 cells/mm2, p = 0.04). There were no significant differences in the spherical equivalent or CCT between the NTG and POAG groups. A significantly lower corneal endothelial cell count was found in NTG compared to POAG.