Treatment of the Diseases of the Eye, by Means of Prussic Acid Vapour, and Other Medicinal Agents is a pioneering 19th-century medical treatise authored by John Stevenson, M.D., F.R.S. This comprehensive work explores innovative approaches to ophthalmology, focusing particularly on the therapeutic use of prussic acid (hydrocyanic acid) vapour in the treatment of various ocular diseases. Drawing from clinical experience and contemporary scientific understanding, Stevenson details the symptoms, causes, and progression of numerous eye conditions, including inflammation, cataracts, amaurosis, and other afflictions that threaten vision. The book meticulously outlines the preparation and administration of prussic acid vapour, emphasizing its potential to alleviate pain, reduce inflammation, and promote healing in cases where conventional remedies had failed. Stevenson supplements his discussion with case studies, observations, and comparative analyses of alternative medicinal agents, such as belladonna, mercury, and other topical or systemic treatments. He also addresses the risks, contraindications, and necessary precautions associated with the use of potent substances like prussic acid, advocating for careful dosing and professional oversight. Beyond its focus on chemical therapies, the treatise delves into the broader context of eye health, offering guidance on hygiene, diet, and lifestyle modifications to support ocular recovery and prevent recurrence of disease. Stevenson’s work reflects the spirit of medical innovation in the early Victorian era, blending empirical evidence with theoretical insight. It stands as a valuable historical document, illustrating the evolution of ophthalmic practice and the quest for effective treatments in a period marked by rapid scientific advancement.