**Question:** Pathognomonic sign of Acute Iridocyclitis is –

A. Iris edema and dilated pupil
B. Intraocular pressure elevation
C. Variable corneal oedema and hypopyon
D. Hypopyon and peripheral ulcerative keratitis

**Correct Answer:** **D. Hypopyon and peripheral ulcerative keratitis.**

**Core Concept:** Acute iridocyclitis is a severe and acute inflammation of the iris and ciliary body, leading to symptoms such as eye pain, redness, and blurred vision. It can be classified as primary or secondary iridocyclitis based on the underlying cause. Pathognomonic signs are distinctive and diagnostic features that directly indicate the presence of a specific disease or condition.

**Why the Correct Answer is Right:**

The pathognomonic signs of acute iridocyclitis are represented by option D: Hypopyon and peripheral ulcerative keratitis.

1. **Hypopyon:** Hypopyon is defined as an accumulation of inflammatory exudates (predominantly white blood cells) within the anterior chamber of the eye. In acute iridocyclitis, hypopyon forms due to the leakage of inflammatory cells and proteins into the anterior chamber from the iris and ciliary body. This sign indicates the presence of an active iridocyclitis, particularly in the context of infectious or inflammatory conditions.

2. **Peripheral ulcerative keratitis:** Peripheral ulcerative keratitis (PUK) is inflammation of the peripheral cornea that occurs in association with iridocyclitis. PUK presents as a peripheral, irregular, and deep ulceration in the cornea. This sign is often seen in cases of infectious iridocyclitis, specifically bacterial or fungal infections. PUK helps differentiate iridocyclitis from other corneal ulcers.

**Why Each Wrong Option is Incorrect:**

A. **Iris edema and dilated pupil:** While iris edema and dilated pupil are clinical findings in iridocyclitis, they are not pathognomonic signs, meaning they can be present in other ocular conditions as well. Consequently, they are not specific to iridocyclitis and do not meet the criteria for a pathognomonic sign.

B. **Intraocular pressure elevation:** Elevated intraocular pressure (IOP) is a potential consequence of acute iridocyclitis, but it is not a direct sign of the disease itself. IOP elevation can be observed in several ocular conditions, limiting its specificity as a pathognomonic sign.

C. **Inflammatory cells in the anterior chamber:** Presence of inflammatory cells in the anterior chamber is common in iridocyclitis as well as other ocular infections and inflammations. Therefore, this sign is not specific to iridocyclitis and does not fulfill the criteria of a pathognomonic sign.

In summary, the correct answer (D) demonstrates the presence of two essential pathognomonic signs of acute iridocyclitis: hypopyon and peripheral ulcer