Given the increasing prevalence of myopia worldwide, particularly in Asian populations, researchers are more concerned than ever about the link between myopia and glaucoma. A new study sheds more light on the effects of optic nerve head (ONH) tilt on visual field (VF) defects in myopic normal tension glaucoma (NTG), possibly paving the way for new screening tools.
A team of Korean researchers found that both horizontal tilt and the angle of maximal tilt correlate with the severity and the location of VF defects in myopic NTG eyes. The team evaluated 112 patients with bilateral myopic NTG, using slit lamp biomicroscopy, Goldmann tonometry, manifest refraction, dilated stereoscopic fundus and disc photography, red-free photography, 30-2 VF testing, axial length measurement, ultrasound pachymetry and enhanced depth imaging (EDI) SD-OCT. Using an inter-eye model, they compared ONH variables between less and more advanced VF defect groups.
The researchers found greater horizontal ONH tilt and greater angular location of maximal ONH tilt were associated with more severe VF defects compared with those with less VF defects. They also noted that a larger number of medications was also associated with more advanced VF defects in myopic NTG. They add that the location of VF defects was associated with the horizontal ONH tilt direction and the angular location of maximal ONH tilt.
“Based on the results, we speculated that the asymmetric myopic changes in myopic NTG may cause axonal damages at different ONH regions under other physiologic conditions including IOP, and ocular and systemic vascular factors,” the study concludes. “These findings are important to advance our understanding of the relations between asymmetric ONH deformation and glaucomatous VF defect in bilateral myopic NTG.”
|Choi JH, Han JC, Kee C. The effects of optic nerve head tilt on visual field defects in myopic normal tension glaucoma. J Glaucoma. January 7, 2019. [Epub ahead of print].