Different Disc Characteristics Associated With High Myopia and the Location of Glaucomatous Damage in Primary Open-Angle Glaucoma and Normal-Tension Glaucoma

: PReCIS:: Disc tilt is a characteristic of high myopia and related to lower wedge-shaped retinal nerve fiber layer (RNFL) defects in normal-tension glaucoma (NTG). In primary open-angle glaucoma (POAG), the direction of disc torsion corresponds to the location of wedge-shaped RNFL defects. PURPOSE: To evaluate the disc characteristics in high myopia and the relationships between disc tilt and torsion and the location of wedge-shaped RNFL defects in primary POAG and NTG. MATERIALS AND METHODS: The differences in disc properties and clinical characteristics between POAG (n=53) and NTG (n=82), and between high myopic (<-6 D, n=77) and non-high myopic (≥-6 D, n=58) glaucoma, were investigated. The association between disc tilt and torsion and the location of wedge-shaped RNFL defects in POAG and NTG were assessed by univariate and multivariate logistic regression analyses. RESULTS: In NTG, but not in POAG, high myopia eyes had significantly smaller discs, a lower tilt ratio (0.73±0.09), and more disc tilt (56.5%) than did non-high myopia eyes (0.80±0.09, 33.3%). In POAG, eyes with lower wedge-shaped RNFL defects had a significantly smaller torsion angle (-5.44±19.62 degrees, inferior disc torsion) than did eyes with upper defects (9.70±23.62 degrees, superior disc torsion; P=0.014). In NTG, a significantly decreased tilt ratio (0.74±0.93; P=0.001) and more disc tilt (55.9%, P=0.005) were found in eyes with lower wedge-shaped RNFL defects than in eyes with upper defects (0.81±0.09; 21.7%). The torsion degree and tilt ratio were the only factors associated with the location of wedge-shaped RNFL defects in POAG and NTG, respectively. CONCLUSIONS: In NTG, smaller and tilted discs were the characteristics of high myopia. Disc tilt was associated with lower wedge-shaped RNFL defects. In POAG, the direction of disc torsion corresponded to the location of the wedge-shaped RNFL defects.