Case Presentation: A 71-year-old man with a history of coronary artery disease (CAD) and percutaneous coronary intervention (PCI) presented to our hospital with unstable angina. He was urgently taken for coronary angiography (CAG) using a trans-radial approach, which revealed three-vessel CAD and severe in-stent restenosis of the left anterior descending artery. Balloon angioplasty was performed successfully with intravascular ultrasound guidance.    During the procedure, the patient received sedation with midazolam and fentanyl. A right radial approach was used, and a 6-French sheath and diagnostic catheters were inserted following administration of local anesthesia with 1% lidocaine. The patient was taking aspirin and clopidogrel, and heparin was used for anticoagulation during PCI with therapeutic-activated clotting time. A total of 250mL of low-osmolar Isovue contrast was used.    One hour after the procedure, the patient developed sudden onset bilateral painless partial vision loss.The patient was immediately evaluated by the stroke team. Pupils were equal and reactive to light, and visual acuity was limited to light perception only. The remainder of the neurological examination was unremarkable. An urgent computed tomography (CT) of the brain followed by a CT angiography of the head and neck was unremarkable. Skin examination did not reveal any manifestations of an allergic reaction. A magnetic resonance (MR) of the brain and an MR angiography of the head and neck were done and were unremarkable. The patient’s visual impairment spontaneously resolved within two hours.

Discussion: Transient cortical blindness (CB) following contrast administration is a rare complication most observed after cerebral angiography, though it has also been reported in patients undergoing coronary angiography. The onset of symptoms varies typically occurring within the first few hours after contrast administration. The pathophysiology leading to CB is unknown. The leading hypothesis is the penetration of contrast through a degenerated blood-brain barrier resulting in a neurotoxic effect on the nerves in the occipital lobe, possibly due to its reduced sympathetic vasoconstriction. Patients typically regain complete vision spontaneously within hours to up to five days, with no long-term visual impairment noted. Despite limited evidence, reducing the volume of contrast administered and using hyperosmolar contrast agents may mitigate this complication.There are reported cases of rechallenging patients with a decreased contrast load prior to CAG with no recurrence of CB. However, a larger sample size must be used to draw definitive conclusions. Additionally, control of underlying risk factors such as hypertension, sepsis, and autoimmune disorders may be useful in preventing CB.

Conclusions: Transient CB after CAG is known but remains a very rare complication. Due to its rarity, preventative measures are not well-established, though patients should still be educated on this complication prior to undergoing catheterization. Treatment is mainly supportive, and the prognosis is excellent.