Usefulness of Optical Coherence Tomography Angiography in the Differential Diagnosis Between Superior Segmental Optic Hypoplasia and Normal-tension Glaucoma

Purpose: The differential diagnosis of superior segmental optic hypoplasia (SSOH) and normal-tension glaucoma (NTG) is an issue in the ophthalmologic field. To date, several modalities have been developed to solve this issue; however, no standard methods have been established. Recently, optical coherence tomography angiography (OCTA) has been introduced to better evaluate the volumetric angiography images. Therefore, in this study, we investigated the usefulness of OCTA in differentiating between SSOH and NTG. Materials and Methods: In this retrospective study, we included 26 patients with SSOH who had definite visual field defects and 40 patients with NTG who had only inferior visual field defects. Age, sex, intraocular pressure, refractive error, retinal nerve fiber layer thickness, and visual field defects were compared between the groups. In addition, we analyzed and compared the peripapillary vessel density (VD) measured on OCTA between the groups. The area under the receiver operating characteristic curves were obtained for each parameter. Results: On Cirrus HD-OCT, the retinal nerve fiber layer in patients with SSOH was thinner in the superonasal segment and thicker in the superotemporal segment compared with patients with NTG. In the analysis of OCTA, the peripapillary VD of the superonasal segment was significantly lower in the SSOH group than in the NTG group, while it was significantly higher in the superotemporal segment in the SSOH group than in the NTG group. The optimal superonasal-to-superotemporal ratio cutoff was 0.8828, with a sensitivity of 95% and specificity of 92.3%, for the diagnosis of SSOH (area under the receiver operating characteristic curve=0.962). Conclusions: Our findings suggest that the superonasal-to-superotemporal VD ratio measured on OCTA may be used to distinguish between SSOH and NTG. However, further large-scale studies are required to verify our findings.