Predicting the risk of parafoveal scotoma in myopic normal tension glaucoma: role of optic disc tilt and rotation

PurposeThe purpose of the study was to evaluate the factors associated with development of parafoveal scotoma in early myopic normal tension glaucoma (NTG).Patients and methodsNinety-nine myopic NTG patients with mean deviation (MD) >-6.0 decibels (dB) were enrolled. Parafoveal scotoma was defined as a visual field (VF) defect within 10° of fixation with at least one point at P<1% lying at the four innermost central points. Systemic factors, optic disc characteristics including tilt ratio, rotation degree, β-zone parapapillary atrophy, disc hemorrhage, and peripapillary retinal nerve fiber layer and macular ganglion cell-inner plexiform layer (mGCIPL) thickness parameters using optical coherence tomography were evaluated. Logistic regression analysis was performed to identify factors associated with the development of parafoveal scotoma.ResultsThe mean spherical equivalent refractive error and MD were -6.07±2.83 diopters and -3.29±1.70 dB, respectively. Among 99 eyes, 42 (42.42%) showed parafoveal scotoma. Eyes with parafoveal scotoma had greater disc tilt, lesser disc rotation, lower MD, thinner minimum mGCIPL, and a higher proportion of VF defect in the superior hemifield than eyes without parafoveal scotoma. Multivariate logistic regression showed that all these parameters were significantly associated with development of parafoveal scotoma (P=0.047, P=0.011, P=0.032, P=0.010, and P=0.001, respectively).ConclusionIn addition to the previously reported risk factors, optic disc characteristics, such as tilt ratio and optic disc rotation, were also significantly associated with development of parafoveal scotoma in patients with myopic NTG.