Okay, let's tackle this question about unilateral afferent pupillary defect. Hmm, the question is asking what happens when light is moved from the normal eye to the affected one. First, I need to recall what an afferent pupillary defect is. From what I remember, it's a problem with the afferent (sensory) pathway of the pupillary reflex. The pupillary light reflex involves both afferent and efferent pathways. The afferent pathway is through the optic nerve and optic tract, and the efferent is through the oculomotor nerve.

So, in a unilateral afferent defect, the issue is on the sensory side. When light is shone into the affected eye, the afferent signal isn't transmitted properly. But the efferent pathway is intact. The swinging flashlight test is used to detect this. When the light is moved from the normal eye to the affected one, the normal eye's pupil might constrict, but the affected eye's pupil doesn't. Wait, but the question is about the response when moving the light from normal to affected. Let me think.

In the swinging flashlight test, if you shine the light in the normal eye, both pupils constrict because the afferent pathway is intact. Then, when you move the light to the affected eye, since the afferent pathway is damaged, the direct response in the affected eye is absent. However, the consensual response (the other eye) also doesn't constrict as much because the afferent input from the affected eye is not there. So, there's a relative dilation of the affected eye's pupil when the light is moved there. This is called the Marcus Gunn pupil. So the answer should be that the affected eye's pupil dilates or shows a paradoxical dilation when the light is moved from the normal to the affected eye.

Now, looking at the options. The correct answer is probably the one that says the affected eye's pupil dilates. The other options might describe other responses like no change, both constrict, or the normal eye constricts. Let me check the options again. The user didn't list them, but the correct answer is the one where moving the light to the affected eye causes the pupil to dilate. So the explanation should focus on the afferent pathway being the issue, leading to the paradoxical dilation in the affected eye during the swinging test.

**Core Concept**
The afferent pupillary defect (Marcus Gunn pupil) results from damage to the optic nerve or retina, impairing the afferent limb of the pupillary light reflex. The swinging flashlight test detects this by observing asymmetric pupillary responses to light.

**Why the Correct Answer is Right**
When light is moved from the normal eye (intact afferent pathway) to the affected eye (damaged afferent pathway), the affected eye’s pupil paradoxically dilates. This occurs because the consensual response from the normal eye weakens when the light shifts, revealing the defective afferent input. The efferent pathway remains intact, so the direct response in the affected eye is absent, but the consensual response also diminishes due to reduced afferent feedback.

**Why Each Wrong Option is Incorrect**
**Option A:** *Pupils constrict equally in both eyes.* Incorrect—equal constriction would indicate an intact

✓ Correct Answer: C. Dilatation in both pupils