Currently, pilots with defective (but correctable) vision are allowed to pilot airliners if they have at least two pairs of their corrective lenses (typically glasses) with them on board.
Was there a specific moment in time when this was first allowed by law and regulations (prior to which persons with defective vision would have been prohibited from piloting an aircraft, even with corrective lenses)? Or has flying with corrective lenses been allowed since the earliest moments of airliners' history?