We investigated the success rates of eyedrop instillation and the distance between the cornea and the dropper tip in 100 volunteers using high-speed digital video recording. Past eyedrop adherence studies assumed that instillation occurred without failure. The ideal distance between the cornea and dropper tip remained unclear, although the general estimate was approximately 2.54 cm (1 inch). This study was approved by the Institutional Review Boards of all participating medical institutions, and all volunteers provided written, informed consent. Successful instillation was defined as when 1 drop fell accurately into the eye on the first attempt. The instillation of ≥2 drops or drops delivered outside the eye was considered a failure. The distance between the eye and dropper tip was measured using still images from a paused digital video camera and a digital ruler. Forty percent of the volunteers instilled eyedrops without instructions from ophthalmologists, pharmacists, or other healthcare workers. When the images were analyzed, the success rate of the first instillation was 70.1%. When the eye was arbitrarily divided into 9 sections, most of the drop sites were the iris or the center of the eye. The distance between the dropper tip and cornea was 2.62±1.75 (median 2.20) cm. These results indicate that the generally recommended distance is usually followed. The successful instillation rate based on the distance from the dropper tip to the cornea was 77% at 1.6±0.88 cm and 54.9% at 4.8±1.25 cm.