Potassium iodate toxic retinopathy: A report of five cases

Background: Potassium iodate (KIO₃) is an iodized salt used for iodine supplementation in areas endemic for goiter. KIO₃ overdose in humans is rare. The authors report unusual cases of retinal toxicity from KIO₃ overdose that caused acute vision loss. Methods: The clinical manifestations, toxic dosage of iodate, and ocular changes in five patients who had taken a KIO₃ overdose were analyzed. Electroretinography, visual evoked potential (VEP), and fundus fluorescein angiography (FA) were performed to study retinal function and changes. Results: Two men and three women (age 22-65 years) ingested KIO₃ solution at a concentration between 187 and 470 mg/kg body weight. Visual acuity ranged from light perception with projection to counting fingers and decreased from 2 to 12 hours after ingestion. Fundus FA showed bilateral extensive areas of retinal pigment epithelial (RPE) window defects, and electroretinography and VEP showed marked impairment of retinal function. Visual acuity improved from counting fingers to 20/80 in 3 months. Conclusion: Potassium iodate can produce retinal toxicity that damages RPE and photoreceptor cells. The recovery of retinal function depends on the amount of chemical absorption, the regeneration of RPE, and the recovery function of photoreceptor cells.