Clinicians caring for patients with normal-tension glaucoma (NTG) and high myopia might want to look a little closer at their optic discs. New research suggests these patients, but not those with primary open-angle glaucoma (POAG), have significantly smaller discs, a lower tilt ratio and more disc tilt overall than NTG patients with non-high myopia.1 While tilted discs are benign congenital anomalies, they may increase a patient’s risk for choroidal neovascularization due to cytokine release from morphological tissue abnormalities.2,3 Smaller discs may be a risk factor for other ocular conditions such as non-arteritic ischemic optic neuropathy.4
The study included 53 patients with POAG and 82 with NTG, all of which had myopia; 77 were deemed high myopes (mean spherical equivalent -8.00±3.00) and 58 non-high myopes (mean spherical equivalent -4.25±3.4). In addition to increased disc tilt and smaller discs, the study found patients with NTG and lower wedge-shaped retinal nerve fiber layer (RNFL) defects had more disc tilt and significantly decreased tilt ratio compared with NTG patients with upper defects. POAG eyes, however, had smaller torsion angles associated with lower-wedge RNFL defects compared with upper defects.1
“In NTG, smaller and tilted discs were the characteristics of high myopia,” the researchers concluded in their paper. “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.”1
1. Lan YW, Chang SY, Sun FJ, Hsieh JW. Different disc characteristics associated with high myopia and the location of glaucomatous damage in primary open-angle glaucoma and normal-tension glaucoma. J Glaucoma. February 15, 2019. [Epub ahead of print].
2. Golnik KC, Payesse EA, Torchia MM. Congenital Anomalies and Acquired Abnormalities of the Optic Nerve. Philadelphia: Wolters Kluwer; 2014.
3. Sowka J, Aoun P. Tilted disc syndrome. Optom Vis Sci.1999;76(9):618-23.
4. Hayreh S. Management of ischemic optic neuropathies. Indian J Ophthalmol. 2011;59(2):123-36.