Question

In a RLR paresis, the secondary deviation isWhen you have the paretic eye fixating. In a pt with a noncomittant or paretic muscle, the 2ndary deviation is much larger than your primary deviation.

a) True
b) False

Answer 1

The statement that the secondary deviation is larger than the primary deviation in the case of a paretic muscle is true.

Step-by-step explanation:

The statement 'In a RLR paresis, the secondary deviation is when you have the paretic eye fixating. In a patient with a noncomittant or paretic muscle, the secondary deviation is much larger than the primary deviation' is true.

In cases like internuclear ophthalmoplegia, a deficit in conjugate lateral gaze occurs due to damage to the abducens nerve or medial longitudinal fasciculus (MLF), affecting the lateral rectus muscle's ability to contract. With a noncomitant strabismus, such as this, when the healthy eye is fixating, it requires less innervation, so the deviation is the primary deviation. However, when the affected or paretic eye is forced to fixate, it requires more innervation to align with the target, leading to a larger deviation from its resting position, known as the secondary deviation.

This essentially happens because of the Hering's law of equal innervation, which states that yoked muscles (i.e., muscles that perform the same movement in both eyes) receive equal neural input. When one muscle is weak (paresis), the other healthy eye's corresponding muscle must overcompensate, resulting in a larger secondary deviation.