There are currently two ways of expressing visual acuity tests, logarithmic and decimal, where 1.0 in decimal is equivalent to 5.0 in logarithmic. Visual acuity examination is one of the important basic examinations in ophthalmology, mainly reflecting the index of visual acuity, that is, the ability of the eyes to distinguish the details of things. It is usually performed by using a standardized vision chart, which has two methods of expression, logarithmic and decimal. The two can be converted to each other. The decimal representation has the advantage of being more intuitive, but the disadvantage that the difference between the numerical gradients is not proportional to the difference between the gradients of visual acuity, e.g., the difference between 0.1 and 0.2 is much greater than that between 0.9 and 1.0, a shortcoming that is overcome by the logarithmic representation.