Disclosed herein are a user device, server, and computer program for determining vision information. The computer program is stored in a computer-readable storage medium including encoded instructions. When executed by one or more processors of a computer system, the computer program causes the one or more processors to perform operations, the operations comprising the operations of: allowing the operation of a lighting unit to be controlled in response to a photographing request； allowing a photographing unit to acquire an image of a pupil of a user in response to the photographing request； allowing intensity profile information regarding the diameter of the pupil to be acquired from the image of the pupil； allowing crescent length information to be determined from the intensity profile information； and allowing the vision information of the user to be determined at least partially based on the crescent length information.
