A 68-year-old woman presents with progressive drooping and eversion of the lower eyelid bilaterally over the past 2 years. She reports chronic tearing, mild conjunctival injection, and occasional mucoid discharge. On examination, the lower eyelid is everted, exposing the palpebral conjunctiva. The eyelid margin is lax and separated from the globe. Horizontal lid laxity is confirmed with a positive snap test. There is no history of facial trauma, surgery, or systemic disease. What is the most likely diagnosis?

Explanation

## Diagnosis: Involutional Ectropion ### Clinical Presentation Analysis The patient presents with bilateral, progressive eversion of the lower eyelid over 2 years in an elderly woman. Key findings include: - **Lid eversion** (ectropion, not entropion) - **Horizontal laxity** (positive snap test) - **No preceding trauma, surgery, or systemic disease** - **Bilateral presentation** (suggests age-related change) - **Tearing and conjunctival irritation** (from loss of lacrimal pump function) ### Pathophysiology of Involutional Ectropion **Mnemonic: LAXITY** — **L**axity of lid tissues, **A**ttenuation of lower lid retractors, **X** (medial **C**anthal tendon laxity), **I**nvolutional changes, **T**endon dehiscence, **Y** (age-related) 1. **Horizontal laxity**: Weakening of the medial and lateral canthal tendons with age. 2. **Vertical laxity**: Attenuation of the lower lid retractors (inferior tarsal muscle, capsulopalpebral fascia). 3. **Orbicularis weakness**: Age-related loss of muscle tone. 4. **Result**: The eyelid margin separates from the globe and everts, exposing the palpebral conjunctiva. ### Snap Test (Positive Indicator of Laxity) - **Procedure**: Gently pull the lower lid away from the globe and release; observe how quickly it returns. - **Positive snap test**: Lid takes >1 second to return to normal position (indicates horizontal laxity). - **Clinical significance**: Confirms the mechanical basis of ectropion. ### Differentiation from Other Forms of Ectropion | Feature | Involutional Ectropion | Cicatricial Ectropion | Paralytic Ectropion | Mechanical Ectropion | |---------|------------------------|----------------------|--------------------|-----------------------| | **Age of onset** | Typically > 60 years | Any age; post-injury | Any age; post-stroke/Bell's | Variable; mass-dependent | | **Mechanism** | Horizontal + vertical laxity | Anterior lamella scarring | CN VII paralysis | Mass effect (tumor, edema) | | **Preceding history** | Gradual age-related | Chemical burn, trauma, SJS | Facial nerve palsy | Orbital pathology | | **Bilateral** | Often bilateral | Usually unilateral | Unilateral (CN VII territory) | Variable | | **Conjunctival appearance** | Normal | Scarred, foreshortened | Normal initially | Normal | | **Snap test** | Positive | Negative/reduced | Positive | Positive | | **Orbicularis function** | Intact | Intact | Weak/absent | Intact | **Key Point:** Involutional ectropion is a diagnosis of **exclusion** — there must be no history of trauma, surgery, systemic disease, or facial nerve palsy. ### Clinical Pearl **High-Yield:** The **positive snap test** in the absence of preceding injury or systemic disease is the hallmark of involutional ectropion. Bilateral presentation in an elderly patient further supports this diagnosis. ### Complications 1. **Lacrimal pump dysfunction**: Loss of the lacrimal canaliculi's ability to drain tears → epiphora (tearing). 2. **Conjunctival irritation**: Chronic exposure of the palpebral conjunctiva. 3. **Corneal exposure**: Risk of keratitis if severe. ### Management 1. **Conservative**: Lubricating drops, protective eyewear, tape support (temporary). 2. **Surgical**: Lower lid tightening procedures (lateral canthoplasty, medial canthoplasty, or full-thickness lid shortening) to restore horizontal and vertical support. ### Why Bilateral Presentation Supports Involutional Diagnosis Involutional changes are systemic and age-related, affecting both eyes symmetrically. Cicatricial, paralytic, and mechanical ectropion are typically unilateral or asymmetric.