Inter-eye differences in myopic patients with unilateral normal-tension glaucoma

Abstract

Purpose: To compare the extent of myopia and axial length (AL) along with other ocular risk factors for the development of open-angle glaucoma between two eyes in bilaterally myopic patients with unilateral normal-tension glaucoma (NTG). Methods: Bilaterally myopic patients with unilateral NTG were consecutively enrolled for this study. Comparison between 2 eyes was performed with regard to intraocular pressure (IOP), mean deviation (MD) and pattern standard deviation (PSD) of the visual field (VF), spectral-domain optical coherence tomography parameters (circumpapillary retinal nerve fiber layer [cpRNFL] thickness, disc area, β-zone parapapillary atrophy [PPA] area), refractive error, and AL. Results: Thirty-six bilaterally myopic patients with unilateral NTG (21 men and 15 women, 41.6 ± 9.3 years) were included. Untreated mean and highest IOP in NTG eyes were not significantly different from those in contralateral non-glaucomatous eyes. VF parameters were worse in NTG eyes than in contralateral non-glaucomatous eyes. The average, superior and inferior quadrants of cpRNFL thickness in NTG eyes were thinner than those in contralateral non-glaucomatous eyes. Compared with contralateral non-glaucomatous eyes, the disc area in NTG eyes was smaller (1.91 ± 0.54 mm2 vs. 2.02 ± 0.50 mm2, p = 0.040), but the β-zone PPA area in NTG eyes was larger (1.40 ± 0.75 mm2 vs. 0.98 ± 0.56 mm2, p < 0.001). NTG eyes had more myopic refractive error and longer AL than contralateral non-glaucomatous eyes (-5.73 ± 1.87 D vs. -4.92 ± 2.01 D, p < 0.001

26.42 ± 1.04 mm vs. 26.08 ± 1.11 mm, p < 0.001). Conclusions: In bilaterally myopic individuals, NTG eyes had more myopic refractive error, longer AL, and larger β-zone PPA areas than contralateral non-glaucomatous eyes. These inter-eye differences in the levels of risk factors for open-angle glaucoma may have contributed to the development of unilateral NTG in myopes.