Superior Segmental Optic Nerve Hypoplasia: A Rare Mimicker of Normal-Tension Glaucoma-A Case Series from Türkiye.

This retrospective case series presents the characteristic features of superior segmental optic nerve hypoplasia (SSONH) in four patients who were initially misdiagnosed with normal-tension glaucoma (NTG), aiming to raise awareness of this rare condition in Türkiye. Four patients (two females and two males) with a mean age of 38 years were included. All were initially diagnosed with NTG and treated with brimonidine drops for three years. Comprehensive ophthalmological examinations were performed, including optic disc photography, optical coherence tomography retinal nerve fiber layer (RNFL) analysis, and visual field testing, with follow-up evaluations conducted over at least one year. Bilateral involvement was observed in two cases, and unilateral involvement in the other two. History of maternal diabetes was noted in 50% of the patients. During medication-free follow-up, all patients demonstrated stable structural and functional parameters, supporting the diagnosis of SSONH. These findings suggest that SSONH should be considered in young patients presenting with superior RNFL thinning and corresponding inferior visual field defects. The non-progressive nature of the condition helps differentiate it from glaucomatous optic neuropathy. Recognizing unilateral cases is essential for avoiding misdiagnosis.