Optic Nerve Canal Variations and Their Surgical Implications: A Ct-based Study Using the Sagar Classification

BACKGROUND: Anatomical variations in the optic nerve canal (ONC) significantly influence surgical risk during endoscopic procedures involving the posterior paranasal sinuses. This study evaluates ONC morphology using the Sagar classification via high-resolution computed tomography (CT), with clinical emphasis on predicting surgical vulnerabilities. MATERIALS AND METHODS: A prospective observational study was conducted over 12 months at a tertiary hospital in North India involving 75 adult patients diagnosed with chronic rhinosinusitis (CRS) according to EPOS 2020 criteria. Bilateral ONCs (N=150) were categorized into four types using CT scans and assessed for bony dehiscence, anterior clinoid process (ACP) pneumatization, and presence of Onodi cells. RESULTS: Type I ONCs were predominant (60%), followed by Type II (14.7%), Type III (13.3%), and Type IV (12%). Type III ONCs had the highest prevalence of bony dehiscence (50%) and ACP pneumatization (68.8%), indicating increased anatomical vulnerability. Onodi cells were seen in 32.7% of cases, further complicating surgical access. CONCLUSION: Detailed CT evaluation of ONC morphology is essential for individualized surgical planning. Type III ONCs, with their high-risk anatomical profile, require particular attention in preoperative imaging due to elevated risk of optic nerve injury.