Background <p>Dysthyroid optic neuropathy (DON) is a vision-threatening complication of Graves’ ophthalmopathy, and insufficient orbital decompression may result in persistent or irreversible visual impairment. While endoscopic transnasal orbital decompression (ETOD) has become a mainstream surgical approach for orbital decompression, the optimal extent of ETOD remains incompletely defined, particularly regarding reproducible anatomical landmarks and safe surgical boundaries.</p> Methods <p>This retrospective study evaluated patients with DON who underwent an extended ETOD procedure at a tertiary medical center. The surgical technique involved decompression of the medial, inferior, and superior orbital walls, with standardized anterior, posterior, superior, and inferior anatomical landmarks. Clinical characteristics, imaging findings, treatment outcomes were reviewed before surgery and during postoperative follow-up. Factors associated with improvement in visual acuity and exophthalmos were further explored.</p> Results <p>Most affected eyes showed postoperative improvement in visual acuity, accompanied by reductions in exophthalmos, intraocular pressure, and lagophthalmos. The extended procedure did not result in major surgical complications or new-onset diplopia. Younger age, poorer preoperative visual acuity, and shorter duration of visual impairment were associated with greater visual recovery, while more severe baseline exophthalmos was associated with greater reduction in exophthalmos. By contrast, diabetes appeared to be associated with less exophthalmos improvement.</p> Conclusion <p>Extended ETOD appears to be a safe and effective surgical strategy for DON. By defining clear anatomical boundaries, this standardized decompression approach may provide clinicians with effective and reproducible surgical guidance and thereby improving patients’ prognosis and psychosocial well-being.</p>