This KnowMed easy note is a scholarly article curated from a government-affiliated medical database focusing on the effects of illicit drugs on the eye. Authored by ophthalmology experts, the paper provides a detailed overview of the various ocular symptoms and vision loss that can result from the use of substances such as alcohol, nicotine, cannabis, opiates, and stimulants. It discusses the routes of drug administration and highlights the importance for clinicians to recognize these ophthalmic signs for accurate diagnosis and timely patient management. The text also includes tables summarizing the frequent visual manifestations and the effects of specific drug categories on pupil size and ocular motility..