Supranormal electroretinogram in a 10-year-old girl with lead toxicity

Purpose To report a case of lead exposure in a 10-year-old girl which resulted in a supranormal ERG and clinical findings of decreased visual acuity, color vision, and stereopsis. Method Case report. Results A 10-year-old girl was exposed to unknown levels of lead, with peak recorded blood levels of 19 mcg/dl 5 years prior to presentation. Lead levels had since normalized. Uncorrected visual acuity was 20/200-OU, improving to 20/80-OU with a refractive correction of +1.50 + 0.75 × 90° OD, +2.50 sphere OS. Color vision was tested with Ishihara plates, and appeared markedly impaired. Stereopsis was grossly impaired, as the patient could not perceive stereoscopic depth with the Titmus “fly” target. Her cognitive function appeared to be slowed and her reaction time also delayed. ERG waveforms were supranormal under photopic and scotopic conditions. Implicit times were normal. Conclusion Lead toxicity with significant visual and cognitive dysfunction, and supranormal ERG, can persist at lead levels below those recognized for lead poisoning.