Final answer:
In RLR paresis, the primary deviation occurs when the left eye fixates.
Step-by-step explanation:
The primary deviation in RLR paresis occurs when the left eye fixates. In RLR paresis, the right oculomotor nerve (or Edinger-Westphal nucleus) is damaged, causing the direct reflex to be lost and the consensual reflex to be intact. As a result, when light is shined in the left eye, the left pupil will constrict while the right pupil does not. This is the primary deviation in RLR paresis.