Visual field asymmetry indices and optical coherence tomography in the differential diagnosis of glaucomatous and pituitary adenoma-related optic neuropathies.

PURPOSE: Differentiating glaucomatous optic neuropathy from compressive optic neuropathy related to pituitary adenomas remains challenging, particularly in patients with mild visual field loss, as structural OCT findings and functional deficits may substantially overlap.

METHODS: This cross-sectional study included 178 eyes of 178 participants with primary open-angle glaucoma, pituitary macroadenomas, pituitary microadenomas, and healthy controls. All subjects underwent standard automated perimetry using the 24 - 2 SITA Standard strategy and spectral-domain optical coherence tomography (OCT). Structural parameters included peripapillary retinal nerve fiber layer (RNFL) thickness, macular ganglion cell-inner plexiform layer (GCIPL) measurements, and the macular naso-temporal ratio (mNTR). Functional asymmetry was assessed using the temporal-to-nasal ratio (TNR), superior-to-inferior ratio (SIR), and an extended Simple Temporal Depression Index (eSTDI), adapted from the original STDI to reduce point-specific variability by sampling a broader region along the vertical meridian. Diagnostic performance was evaluated using receiver operating characteristic (ROC) analysis.

RESULTS: Peripapillary RNFL and macular GCIPL analyses demonstrated characteristic but overlapping structural patterns between glaucoma and macroadenoma groups, whereas no significant structural abnormalities were observed in the microadenoma group compared with controls. The mNTR showed limited discriminatory ability across group comparisons. By contrast, visual field-based asymmetry indices, particularly eSTDI, demonstrated strong diagnostic performance, while structural OCT parameters and functional indices provided complementary diagnostic information across different group comparisons. The eSTDI effectively differentiated glaucoma, macroadenoma, and microadenoma groups from healthy controls but showed limited ability to distinguish glaucoma from macroadenoma. Importantly, patients with pituitary microadenomas exhibited significant functional visual field abnormalities compared with controls despite the absence of corresponding structural abnormalities on OCT.

CONCLUSIONS: Visual field-based functional asymmetry indices, particularly eSTDI, may help identify abnormal visual pathway involvement in early or subtle disease, especially when structural OCT findings are inconclusive. Nevertheless, structural OCT remains essential for the topographic assessment of RNFL and GCIPL damage. While eSTDI reliably identifies abnormal functional patterns, its discriminatory capacity is reduced when disease entities exhibit similar levels of functional impairment. These findings support an integrated multimodal approach in which structural OCT and visual field-based asymmetry indices provide complementary information in the differential diagnosis of glaucomatous and compressive optic neuropathies.