Pupil in acute iritis is:
**Core Concept**
In acute iritis, the iris is inflamed due to an immune response or infection, leading to a disruption in the normal pupillary response. This condition can cause the pupil to constrict due to spasm of the iris sphincter muscle or due to the release of chemical mediators that cause miosis.
**Why the Correct Answer is Right**
The correct answer is that the pupil is constricted in acute iritis. This occurs due to the release of acetylcholine from the ciliary ganglion, which stimulates the iris sphincter muscle to contract and cause miosis. Additionally, the release of prostaglandins and other chemical mediators can also contribute to the constriction of the pupil.
**Why Each Wrong Option is Incorrect**
**Option A:** The pupil is dilated in acute iritis. This is incorrect because the pupil is typically constricted in acute iritis due to the mechanisms mentioned above.
**Option B:** The pupil is not affected in acute iritis. This is incorrect because the pupil is often affected in acute iritis, with constriction being a common finding.
**Option C:** The pupil is irregularly shaped in acute iritis. This is incorrect because while the pupil may be irregularly shaped due to inflammation of the iris, constriction is a more characteristic finding in acute iritis.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that in cases of acute iritis, the pupil may be constricted due to spasm of the iris sphincter muscle or the release of chemical mediators. This can help differentiate iritis from other causes of miosis, such as third nerve palsy.
**Correct Answer: C. The pupil is constricted in acute iritis due to spasm of the iris sphincter muscle or the release of chemical mediators.**