The deviation of the paretic eye when the normal eye is fixating is known as the ___________ deviation.

• A. Primary deviation
• B. Secondary deviation
• C. Tertiary deviation
• D. Quaternary deviation

Answer: (A)

In strabismus, the amount of misalignment changes depending on which eye is fixing due to shared neural innervation. The deviation of the paretic eye when the normal eye is fixating is called the primary deviation. It’s the standard reference measurement because it shows how the paretic eye itself deviates in primary gaze without the influence of the paretic eye trying to fix. When the paretic eye fixes, the normal eye tends to deviate more—this is the secondary deviation, and it reflects the increased innervation needed under that condition. The other terms describe less commonly used or different fixation scenarios and aren’t the standard name for this situation.