In case of anisocoria when 1% pilocarpine is instilled into the eye with abnormally dilated pupil, pupil remains dilated. Cause of anisocoria may be-
**Core Concept**
The pupillary light reflex is controlled by the autonomic nervous system, specifically the parasympathetic and sympathetic pathways. Pilocarpine is a muscarinic receptor agonist that stimulates the parasympathetic pathway, causing pupillary constriction. Anisocoria refers to an uneven pupil size, which can result from various causes, including oculomotor nerve palsy, third cranial nerve compression, or Horner's syndrome.
**Why the Correct Answer is Right**
In cases of anisocoria, the dilated pupil may not respond to pilocarpine due to a disruption in the parasympathetic pathway. If the oculomotor nerve (third cranial nerve) is damaged or compressed, the parasympathetic fibers responsible for pupillary constriction will be affected, resulting in a lack of response to pilocarpine. This is because pilocarpine acts on the muscarinic receptors in the iris sphincter muscle, which is controlled by the parasympathetic pathway.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not provide a plausible explanation for the lack of response to pilocarpine.
**Option B:** This option is incorrect because it is a distractor and does not relate to the clinical scenario described.
**Option C:** This option is incorrect because it does not accurately describe the cause of anisocoria in this scenario.
**Clinical Pearl / High-Yield Fact**
When assessing anisocoria, it is essential to perform a full neurological examination, including assessing the pupillary light reflex, corneal reflex, and extraocular movements. This will help identify the underlying cause of the anisocoria and guide further management.
**Correct Answer:** C.