Electroretinograms (ERGs) are diagnostic test that evaluates the response of the cells in the retina (inner layer of the eye) to light stimulI. Many of our studies, especially in neuro-ophthalmology, utilize ERGs. These tests are used to detect and follow a number of eye conditions such as chloroquine/hydroxychloroquine toxicity, Leber’s optic hereditary optic neuropathy, retinitis pigmentosa to name a few.