A 68-year-old man presents with lower eyelid ectropion causing epiphora and conjunctival injection. Which of the following is the MOST COMMON cause of ectropion in this age group?

Explanation

## Involutional Ectropion: Epidemiology and Pathophysiology **Key Point:** Involutional (senile) ectropion is the most common form of ectropion in the elderly, caused by age-related laxity of the eyelid support structures. ### Pathophysiology of Involutional Ectropion 1. **Horizontal lid laxity** — stretching of the medial and lateral canthal tendons 2. **Loss of eyelid tone** — atrophy and weakening of the orbicularis oculi and Müller's muscle 3. **Gravity and repeated blinking** — chronic mechanical stress causes progressive eversion 4. **Enophthalmos** — backward displacement of the globe reduces support for the lid margin ### Clinical Features - Occurs almost exclusively in the **lower lid** - Gradual onset in patients >60 years - Symptoms: epiphora (tearing), conjunctival injection, foreign body sensation - **Snap test** shows delayed return (lid laxity) - **Distraction test** shows >6 mm horizontal laxity ### Differential Diagnosis of Ectropion | Type | Cause | Lid Affected | Age | Key Feature | | --- | --- | --- | --- | --- | | **Involutional** | Lid + canthal laxity | Lower | >60 | Gradual, painless | | **Paralytic** | CN VII palsy | Lower | Any | Acute onset, inability to close eye | | **Cicatricial** | Scar contracture | Upper or lower | Any | History of trauma/burn/SJS | | **Mechanical** | Mass/edema | Lower | Any | Visible mass or swelling | | **Spastic** | Orbicularis spasm | Lower | Any | Associated with irritation | **High-Yield:** The **snap test** is the clinical gold standard for diagnosing involutional ectropion — the everted lid should snap back to normal position within 1 second when released; delayed return (>1 second) indicates laxity. **Clinical Pearl:** Involutional ectropion often coexists with dermatochalasis (excess eyelid skin), but dermatochalasis alone does NOT cause ectropion unless accompanied by lid laxity. The distinction is important because surgical management differs: ectropion requires canthal tightening, while dermatochalasis requires skin excision only. **Mnemonic: LACE** — Laxity, Age, Canthal stretching, Enophthalmos (the four pillars of involutional ectropion). [cite:Yanoff & Duker Ophthalmology 5e Ch 7]