**Question:** Which agent is used to prevent synechiae after DCR surgery?

**Core Concept:** DCR (Dacryocystorhinostomy) surgery is a procedure that involves creating a new drainage pathway for the tears from the lacrimal sac to the nasal cavity, commonly performed to treat acquired or congenital nasolacrimal duct obstructions. Synechiae refer to the formation of fibrous tissue bonds between two adjacent structures.

**Why the Correct Answer is Right:** Phenol is a potent alkylating agent used to prevent scarring and fibrosis after DCR surgery. It works by causing cross-linking of proteins, reducing collagen synthesis and damaging the DNA, ultimately inhibiting fibroblast proliferation and reducing tissue repair processes.

**Why Each Wrong Option is Incorrect:**

A. Mitomycin C (MMC) is an antimetabolite drug that is used to prevent fibrosis and scarring after various surgical procedures, including DCR. However, it is not specific for preventing synechiae formation compared to phenol.

B. Tobramycin is an antibiotic used to treat infections, not to prevent fibrosis and synechiae formation after DCR surgery.

C. Betamethasone is a corticosteroid used for its anti-inflammatory and immunosuppressive properties, but it is not specifically designed to prevent synechiae formation in DCR patients.

D. Cyanoacrylate glue (e.g., Histoacryl) is a tissue adhesive used for sealing and hemostasis during surgery, but it is not effective in preventing synechiae formation post-operatively in DCR patients.

**Clinical Pearl:** Phenol is a potent and effective agent for preventing synechiae formation after DCR surgery due to its strong anti-fibrotic and anti-proliferative properties. However, its use is limited by its high toxicity and potential complications, such as chemical conjunctivitis, corneal ulceration, and impaired wound healing.

**Correct Answer:** Phenol (Option A) is the correct answer as it is a potent anti-fibrotic agent, which helps in preventing synechiae formation after DCR surgery. The other options (MMC, Tobramycin, Betamethasone, and Cyanoacrylate glue) are not specifically designed for preventing synechiae formation, making them incorrect choices.