Normal-tension glaucoma in high myopia is associated with the presence of posterior staphyloma and subfoveal scleral thinning

Abstract

Purpose: To evaluate the ocular biometry in patients with normal-tension glaucoma (NTG) and highly myopic eyes and to identify the ocular parameters significantly associated with the biomechanical changes of high myopia and glaucomatous optic neuropathy.Materials and Methods: The study included 45 patients with NTG and 38 controls with highly myopic eyes (≤ -6 diopters (D) or axial length ≥ 26.0 mm). The subfoveal retinal, choroidal, scleral thickness and the posterior staphyloma heights were examined from enhanced depth imaging spectral-domain optical coherence tomography (EDI-OCT). Scleral thickness and posterior staphyloma height in patients with highly myopic NTG was compared with those in highly myopic, non-glaucomatous eyes. A Pearson correlation was calculated to assess the relationships of scleral thickness and posterior staphyloma height with ocular parameters. Multiple regression analysis was performed to identify the ocular parameters significantly associated with the changes of scleral thickness and posterior staphyloma height. Results: Subfoveal scleral thickness could be measured in 32(71.1%) and 24(63.2%) of highly myopic NTG and highly myopic eyes, respectively. Highly myopic NTG eyes had thinner subfoveal scleral thickness (473.03 ± 43.75 versus(vs). 579.46 ± 75.87 ㎛, P < .001) and higher posterior staphyloma (97.80 ± 70.19 vs. 62.83 ± 32.01 ㎛, P = .027) than highly myopic, non-glaucomatous eyes. Subfoveal scleral thickness was significantly correlated with age (r = -0.453, P =.014), axial length (r = -0.343, P=.040), corneal hysteresis (CH) (r = 0.460, P = .010), and the posterior staphyloma height of superior quadrant (r = -0.538, P = .003), nasal quadrant (r = -0.519, P = .004) and the sum of four quadrants (r = -0.424, P = .022) in highly myopic NTG eyes. Corneal hysteresis (B = 2.694, P = .015), corneal resistance factor (B=-2.916, P = .010) and the posterior staphyloma height of nasal quadrant (B = -0.463, P = .017) were most significantly associated with the subfoveal scleral thickness in highly myopic NTG eyes.Conclusion: Subfoveal scleral thinning and ununiform posterior staphyloma formation were closely related in highly myopic NTG eyes. CH may be a clinically useful parameter to demonstrate the biomechanical material properties such as scleral stiffness.