Visual acuity is the visual acuity, which mainly reflects the visual function of macular area, and can be divided into distance vision and near vision, while in the clinical diagnosis, it is often necessary to check the corrected visual acuity (i.e. the visual acuity after optometry and lens correction). The most commonly used distance visual acuity examination is the international standard visual acuity table, and the normal visual acuity standard is 1.0. If, during the examination, the examined person’s visual acuity is found to be lower than 1.0, a small hole lens is often added for further examination. If the subject’s visual acuity is below 1.0 or if there are factors that may affect visual acuity, a full distance, near, and corrected visual acuity examination of the subject’s eye is required to determine the degree of visual impairment. The near vision examination is a reading vision examination, the purpose of which is mostly to compare with the distance vision and to clarify part of the diagnosis (e.g. refractive error, presbyopia, etc.), and also to more correctly assess the subject’s activity as well as reading ability. For example, newborns can be examined by “chasing the light” or observing the pupil’s reflex to light, 1-month-old children can actively browse around, and 3-month-old children can be examined by gaze. The more commonly used test is the optokinetic nystagmus test, which assesses visual acuity by observing the child’s trailing gaze for a wide or narrow bar. Visual acuity testing is important for the diagnosis of clinical conditions in ophthalmology, and the choice of testing modality and test is based on the patient’s age and ocular health status.