Reversible cortical blindness secondary to acute carbon monoxide poisoning

Abstract

Introduction
Carbon monoxide (CO) poisoning can result in multi-system organ dysfunction. While neural and neuropsychiatric manifestations are widely reported, cortical vision loss due to CO poisoning is rarely seen in routine clinical practice. This report highlights a case of acute cortical blindness due to carbon monoxide poisoning that completely resolved with hyperbaric oxygen therapy.
Report
A 29-year-old male plumber with a past medical history of sickle cell trait and no ocular history presented to the emergency department after being found unconscious beside a leaking boiler tank. Upon awakening, he endorsed bilateral vision loss. His initial examination was notable for disorientation except to self and bilateral blindness, with the remainder of his neurologic examination as non-focal. His oxygen saturation was 70% and carboxyhemoglobin level at the scene was over 125 parts per million. Ophthalmic evaluation was notable for absent blink-to-threat bilaterally and hand-motion visual acuity in both eyes. Otherwise, the patient had briskly reactive pupils and no afferent pupillary defect. Dilated fundoscopy demonstrated healthy-appearing optic discs without edema or pallor and no retinal lesions. Hyperbaric oxygen therapy was initiated. On the second day of admission, the patient reported subjective resolution of the blindness, which was confirmed by objective bedside testing that showed normal visual acuity, full visual fields, and full color perception in both eyes. An in-office examination one week later was similarly reassuring, with supplementary optical coherence tomography revealing normal retinal nerve fiber layer and ganglion cell layer thickness in both eyes.
Conclusion
CO poisoning can lead to acute vision loss due to cortical blindness, even in the absence of other focal neurologic deficits. Knowledge of this entity can reduce the time to diagnosis in patients who present similarly and allow timely treatment with hyperbaric oxygen to reverse vision loss, even when other neurological symptoms have spontaneously improved.