Differentiating superior segment optic nerve hypoplasia from normal-tension glaucoma in Chinese patients

Careful interpretation of optical coherence tomography findings facilitates recognition of superior segment optic nerve hypoplasia (SSONH). This helps distinguish SSONH from normal-tension glaucoma, prevents unnecessary treatment, and enables for appropriate patient monitoring during clinical practice.

Literature regarding Chinese SSONH patients remains undocumented. Previous studies focused mainly on cases with visual-field defects. This study aims to explore methods for differentiating SSONH and early-stage normal-tension glaucoma.

This retrospective study included SSONH (n = 22), normal-tension glaucoma (n = 22) and control (n = 20) eyes. Retinal nerve fibre layer and ganglion cell complex thickness were combined for differential diagnosis. Optimal cut-off values were chosen based on clinical requirement weighing sensitivity and specificity.

Retinal nerve fibre layer thinning was observed in SSONH eyes except temporal-inferior quadrant, and in normal-tension glaucoma eyes except temporal-upper sector. Ganglion cell complex thinning was pronounced in normal-tension glaucoma eyes and superior hemi of SSONH eyes. Compared to the normal-tension glaucoma group, retinal nerve fibre layer of SSONH eyes was thinner in nasal-superior hemi and thicker in temporal-inferior quadrant. When the ratio of inferior-temporal octant thickness to superior-nasal octant thickness ≥1.788 or the ratio of temporal-inferior to nasal-superior quadrant retinal nerve fibre layer thickness ≥1.387, the sensitivity and specificity for identifying SSONH are 77.27% and 100.00%. When inferior-hemi ganglion cell complex thickness ≥85 μm the same retinal nerve fibre layer ratio ≥1.101, the sensitivity and specificity reached 91.11% and 88.43%. To differentiate SSONH from controls, the best-performing parameter was sum of nasal superior 3/4 retinal nerve fibre layer at 529 μm.

The specific retinal nerve fibre layer and ganglion cell complex thinning patterns of SSONH and normal-tension glaucoma patients may help with differentiation. Combining retinal nerve fibre layer and ganglion cell complex thickness may provide additional value in recognising SSONH.