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

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

Answer: (B)

In strabismus terminology, how a deviation is described depends on which eye is fixing. When the paretic eye is the one attempting to fix, the other, normally functioning eye deviates in the opposite direction. This is called the secondary deviation. It reflects the brain’s coordinated innervation to both eyes (Hering’s law) while one eye’s muscle is weak, so the nonparetic eye shows the misalignment more clearly. The alternate situation—where the paretic eye fixes and the deviation is observed in that eye—would be the primary deviation. Terms like tertiary or compensatory deviation aren’t used for this specific scenario.