Which method is a subjective way to determine the magnitude of a deviation that uses a Maddox rod?

• A. Alternating cover test
• B. Unilateral cover test
• C. Von Graefe phoria
• D. Maddox rod testing

Answer: (D)

A key way to quantify a deviation that relies on what the patient sees is the Maddox rod test. Here, a Maddox rod is placed in front of one eye, turning a point light into a visible line for that eye, while the other eye still sees the fixation light. The test hinges on the patient reporting how that line relates to the fixation point or reference sight. By adjusting prisms until the line and the point appear aligned, you obtain the amount of prism needed to achieve alignment, which is the magnitude of the deviation in prism diopters. Because the measurement depends on the patient’s perception of line orientation rather than purely on observing the eyes, it’s considered a subjective test.

In contrast, other methods in this context rely more on the clinician’s observation of eye alignment or on dissociating the eyes without relying on the patient’s perceptual judgment of a line, which is why the Maddox rod technique uniquely provides a subjective measure with a Maddox rod.