Certified Ophthalmic Technician Practice Test 2025 – Complete Exam Prep

The best method for measuring a deviation with good fixation is the prism alternate cover test. This technique is specifically designed to assess the magnitude of a strabismus (misalignment of the eyes) while the patient maintains fixation. During the test, a prism is placed in front of one eye to measure the amount of deviation by observing the eye movement when the cover is switched between the two eyes. The test can effectively quantify the degree of deviation under conditions that simulate natural visual tasks, making it a reliable choice for measuring eye alignment accurately.

In contrast, the cover-uncover test is generally used to determine the presence of a deviation rather than to measure its degree. While it can indicate misalignment, it does not provide a quantitative measurement of the angle of deviation like the prism alternate cover test does. Visual acuity tests focus on the clarity or sharpness of vision rather than on eye alignment. A diplopia grid is used primarily to assess and measure diplopia (double vision) but is not typically applied for measuring deviations in eye alignment. Therefore, the prism alternate cover test stands out as the most effective method for measuring a deviation while maintaining good fixation.