Effects of Axial Lengths in High Myopia on the Significance Maps of Optical Coherence Tomography

Abstract

Purpose: We corrected the axial lengths of the macular and peripapillary significance maps using software embedded in a commercial spectral domain optical coherence tomography (SD-OCT) package. We evaluated the accuracy of glaucoma diagnosis in patients with high myopia, and the clinical implications.Methods: Seventy eyes of 70 highly myopic patients with or without normal-tension glaucoma were retrospectively reviewed. The sensitivities and specificities of the color-coded significance maps were calculated using 1% (red) or 5% (yellow) as the abnormality criteria, and the values compared before and after axial length corrections performed using embedded SD-OCT software.Results: At the 1% level of the normative database, we found no significant difference in specificity or sensitivity. At the 5% level, the increase in specificity was significant only for the inferotemporal sectors of the macular significance map. The specificity of the inferotemporal sector of the inner scan circle increased from 61.9 to 78.6% (p = 0.016) and that of the outer scan circle from 69 to 83.8% (p = 0.031). The specificities of the entire chart, the superior sector of the superior/inferior chart, and the 12-clockwise map increased significantly from 54.8 to 78.6% (p = 0.002), 59.5 to 76.2% (p = 0.039), and 59.5 to 76.2% (p = 0.002) respectively.Conclusions: Clinicians should note that axial length correction of significance maps reduces the false-positive glaucoma diagnostic rates in highly myopic eyes. Correction of significance maps using embedded software may thus aid clinicians in the diagnosis of glaucoma in high myopic eyes.