In 1884, Sigmund Freud asked Viennese ophthalmologist Dr Karl Koller to work with coca leaves. Dr Koller was looking for a procedure or agent to use during eye operations. Eye operations often needed a conscious, awake subject. Before the advent of local anaesthetia, such operations were fiendishly difficult for the surgeon and profoundly distressing for the patient.
The numbing effect of chewing coca leaves had long been known; but this action had long been disregarded as an unwanted side-effect. Dr Koller realised that cocaine was an ideal local anaesthetic for eye surgery, its only real drawback being that it is also an eminentlty abusable euphoriant.
Refs and Further Reading
Anaesthesia and Anaesthetics