Posterior Ischemic Optic Neuropathy Secondary on Direct Carotid Cavernous Fistula: A Rare Case Report

Background: Direct carotid-cavernous fistula (CCF) is a pathological arteriovenous connection between the internal carotid artery and the cavernous sinus, commonly resulting from craniofacial trauma. Posterior ischemic optic neuropathy (PION) is an uncommon but vision-threatening complication of traumatic CCF. Case Report: A 45-year-old woman presented with a one-week history of left eye swelling, double vision, ocular pain, redness, tearing, and progressive visual loss following a traffic accident. Left eye examination showed 2 meters counting finger visual acuity, 25 mmHg intraocular pressure, ocular movement limitation, superior visual defect, decreased colour vision and contrast sensitivity. Anterior segment findings included proptosis, eyelid swelling, 180degree inferior chemosis, conjunctival injection, dilated corkscrew episcleral vessel, positive rapid anterior pupillary defect. Significant improvement followed after endovascular treatment. Discussion: The coexistence of direct CCF and PION is exceptionally rare. This case showed atypical visual loss without disc edema. The likely mechanism involves arterial steal and venous congestion. Early intervention led to partial visual recovery. Prompt recognition and ophthalmologic monitoring are essential to improve visual outcomes in CCF-associated PION. Conclusion: Early collaborative management is vital in cases of traumatic CCF with PION to prevent disease progression, preserve visual function, and achieve optimal outcomes.