Purpose: When we look at the object, we used the dominant eye mainly. For this reason, a prescription of the dominant eye is an important factor for glasses and contact lenses. This study evaluated visual acuity differences between dominant and nondominant eyes through analyzing refractive power changes in both eyes by the ages. Methods: This study was performed to investigate the relationship between refractive error and dominant eye which had the superiority in the function of binocular. 186 subjects without ocular disease were examined on the dominant eye. The dominant eye was examined by the Hole-in-the-card test. For the consistency of the measurements, we tested refractive power in three times by the same person. Results: Using SPSS, the relationship between vision and the dominant eye was analyzed. 135 people of the whole subjects have the dominant eye on right. The Number of the non-dominant eye is 51. We were divided into 3 types, the group under the age of 10 that begins to expose environment factor affect on vision (the average age $8.8{pm}1.18$) and the age group of 10 to 20 that begins to change refractive power in earnest (the average age $14.1{pm}2.58$) and the group after the age 20 that began to stabilize vision (the average age $51.8{pm}17.51$). The visual acuity of dominant eye was higher than non-dominant eye in all age groups. Nevertheless, these results were not statistically significant. Mean astigmatism of dominant eye was smaller than the non-dominant eye, and this is significant, statistically (p=0.017<0.05). Conclusions: It is expected that the balanced eye with a lower level of astigmatism has a more possibility become a dominant eye.