Posterior synechiae in anterior uveitis result from adhesion of which two structures?

Explanation

## Posterior Synechiae: Anatomy and Pathophysiology **Key Point:** Posterior synechiae are adhesions between the iris and the anterior lens capsule. They form when inflammatory exudate causes the iris to adhere to the lens during the acute phase of anterior uveitis. ### Definition and Formation **Synechiae** are adhesions between structures in the anterior segment: | Type | Structures Involved | Clinical Significance | | --- | --- | --- | | **Posterior synechiae** | Iris to anterior lens capsule | Most common; leads to iris bowing, pupillary distortion, and potential angle-closure if 360° | | **Anterior synechiae** | Iris to corneal endothelium | Occurs in severe inflammation; can cause angle closure and secondary glaucoma | | **Seclusio pupillae** | Complete 360° posterior synechiae | Iris is completely adherent to lens; pupil becomes non-reactive | | **Occlusio pupillae** | Fibrinous membrane covers pupil | Rare; severe inflammation | **High-Yield:** Posterior synechiae are a hallmark of anterior uveitis. Their presence indicates significant inflammation and risk of complications. Prevention with mydriatics (cycloplegics) is a key treatment goal. ### Mechanism of Formation 1. Inflammatory exudate accumulates in the anterior chamber. 2. Fibrin and inflammatory cells coat the iris surface. 3. The iris is pushed forward against the lens by aqueous pressure and exudate. 4. Fibrin bridges form between iris epithelium and lens capsule. 5. Over time, these bridges organize and become permanent adhesions. **Clinical Pearl:** Aggressive mydriatic therapy (tropicamide 1% or homatropine 5% QID) is used to prevent posterior synechiae by keeping the iris away from the lens and maintaining pupillary movement. ### Complications of Posterior Synechiae - **Iris bowing:** Forward displacement of iris due to 360° adhesions. - **Pupillary distortion:** Irregular pupil shape; loss of normal reflex. - **Angle-closure glaucoma:** If 360° synechiae form, iris is pushed forward, narrowing the angle. - **Posterior synechiae-related glaucoma:** Even partial synechiae can elevate intraocular pressure.