Multimodal imaging in iodate-induced toxic retinopathy

Iodine deficiency is a leading cause of preventable physical and mental retardation. Potassium iodate is used for iodine supplementation to prevent iodine deficiency. We herein report a case of toxic retinopathy following intentional ingestion of potassium iodine.

A 41-year-old male presented with a 5-day history of blurred vision in both eyes. His visual acuity (VA) was hand motion and his pupillary reactions were sluggish bilaterally. The fundus examination revealed bilaterally diffuse retinal pigment epithelium atrophy and secondary pigmentary changes at the posterior pole, but his peripheral fundus was relatively spared. Choroidal thinning, punctate hyperreflective dots along the retinal pigment epithelium layer, and outer retinal atrophy were the optical coherence tomography findings, which were consistent with widespread areas of retinal pigment epithelium window defects observed on fundus fluorescein angiography. The visual evoked potential test showed no response in the right eye and revealed a delay in the latency and a decrease in the amplitude of the P100 wave in the left eye. Wave b responses of the photoreceptors could not be observed in the patient's electroretinogram. After a vitamin supplementation protocol consistent with the literature, at the 4-month follow-up visit his visual acuity had improved to 0.3 in the right eye and counting fingers in the left eye.

Potassium iodate toxicity is a cause of serious retinal and choroidal damage and results in severe vision loss. Hydration, hemodialysis, and antioxidants can be helpful to minimize the complications.