## **Core Concept**
Chronic dacrocystitis refers to a persistent inflammation of the lacrimal sac, often resulting from a blockage in the nasolacrimal duct. This condition can lead to recurrent or persistent infection and swelling of the lacrimal sac. The underlying cause is usually related to an obstruction in the tear drainage system.

## **Why the Correct Answer is Right**
The correct answer, **D. Blockage of nasolacrimal duct**, is right because chronic dacrocystitis typically occurs due to a blockage in the nasolacrimal duct, which prevents tears from draining properly into the nasal cavity. This blockage can lead to stasis of tears, infection, and subsequent inflammation of the lacrimal sac. The blockage can be due to various reasons including stones (dacryoliths), scarring, or tumors.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is blank and does not provide a reason, making it impossible to assess its accuracy.
- **Option B:** Similarly, this option is blank and lacks any information to evaluate its correctness.
- **Option C:** This option is also blank, providing no details to determine why it might be incorrect.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that chronic dacrocystitis often presents with a painful swelling in the area of the lacrimal sac (medial canthus), and may result in a mucocoele or a chronically infected lacrimal sac. A common treatment is dacrocystorhinostomy (DCR), a surgical procedure that aims to restore the flow of tears into the nasal cavity by creating a new passage.

## **Correct Answer:** D. Blockage of nasolacrimal duct.