After the man stopped using the mouthwash, his vision improved, the authors wrote. With only one other similar case reported in the literature, the report raises awareness that chronic ingestion of over-the-counter mouthwash may lead to toxic optic neuropathy.
"Chronic mouthwash ingestion should be avoided since it is able to cause severe visual loss even in the absence of other risk factors," wrote coauthors, Drs. Rod Foroozan and Francesco Pellegrini of Baylor College of Medicine in Houston (Surv Ophthalmol, May 18, 2022).
A 77-year-old man with painless vision loss
For one year, the man experienced painless vision loss in both eyes. Due to his high blood pressure, he was taking aspirin and atenolol, but otherwise was healthy.
Despite undergoing cataract extraction a few months earlier, the man's visual acuity continued to decrease. A neurological exam and a contrast-enhanced brain magnetic resonance imaging (MRI) scan revealed nothing unusual. Also, the man underwent genetic testing for Leber hereditary optic neuropathy and autosomal dominant optic atrophy, as well as testing for complete blood count, comprehensive metabolic panel, C-reactive protein, erythrocyte sedimentation rate, vitamin B12, and serum thiamine. All results were within normal limits, the authors wrote.
The patient underwent a macular optical coherence tomography (OCT) scan, which was unremarkable. Also, his peripapillary retinal nerve fiber layer thickness was within normal limits, they wrote.
Clinicians determined that the man's visual field defect was central and extending into his blind spot, which implied that he was experiencing optic neuropathy or maculopathy. Since his OCT scan was normal and decreased ganglion cell complex measures were identified in each eye, it was suspected that optic neuropathy likely caused his decreased vision.
Common causes of this type of vision field loss include toxic or nutritional optic neuropathy and hereditary optic neuropathy. Since dominant optic atrophy causes chronic progressive visual loss over years, this was unlikely to cause his vision impairment. Alcohol consumption, toxicity to heavy metals, and vitamin deficiencies can cause toxic optic neuropathy. Therefore, a thorough medical history is critical, they wrote.
To confirm the diagnosis, the patient was questioned further. The man reported eating meat, drinking less than one glass of wine per day, and not smoking, and his family history was negative for eye diseases.
Eventually, the patient admitted that 18 months earlier, he had undergone a root canal. Since the endodontic procedure, he reported consuming a glass of mouthwash at least three times per day after toothbrushing. Based on the exam and the history, the man was diagnosed with bilateral toxic optic neuropathy, the authors wrote.
After discontinuing the mouthwash, the man's vision improved. At a three-month follow-up visit, his vision remained improved, they wrote.
Nevertheless, "chronic ingestion of mouthwash can lead to a bilateral toxic optic neuropathy even in the absence of other risk factors," Foroozan and Pellegrini wrote.
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