One such evaluation method is reliability. A reliable test is one that will give the same result when repeated on multiple occasions (i.e. test-retest reliability) or by different people (inter-rater reliability). An unreliable test gives widely varying results when repeated, which would make changes in a patient's test results difficult to interpret. Therefore, this study aims to determine the test-retest reliability of seven binocular vision tests across two independent measurements. The investigators will measure 20 healthy people ages 18 to 35 years for each of these tests on two separate occasions, one week apart. Since these tests have been in use for many years, we are expecting the two measurements to be within acceptable range of each other.