Contact Lens — MCQs

Q: Ectopia lentis is a feature of which of the following conditions?

All of the above. **Explanation:** **Ectopia lentis** refers to the displacement or malposition of the crystalline lens from its normal anatomical location in the ciliary body. This occurs due to the dysfunction, weakness, or rupture of the **zonules of Zinn** (suspensory ligaments). **Why "All of the above" is correct:** Ectopia lentis is a hallmark feature of several systemic connective tissue disorders: * **Marfan’s Syndrome:** This is the most common cause of heritable ectopia lentis. It is an autosomal dominant disorder (FBN1 mutation) where the lens typically displaces **superotemporally** (Upward and Outward). The zonules usually remain intact but are stretched. * **Homocystinuria:** An autosomal recessive metabolic disorder. Unlike Marfan’s, the lens displacement is typically **inferonasal** (Downward and Inward). A key distinction is that zonules are brittle and completely broken due to a deficiency in cystathionine beta-synthase. * **Weill-Marchesani Syndrome:** A rare systemic disorder characterized by short stature and brachydactyly. It features **microspherophakia** (small, spherical lens), which is prone to **downward** subluxation and can lead to pupillary block glaucoma. **High-Yield Clinical Pearls for NEET-PG:** 1. **Direction Mnemonic:** Marfan’s = **M**ore (Up); Homocystinuria = **H**omeless (Down). 2. **Systemic Association:** Patients with Homocystinuria have an increased risk of thromboembolism (important for surgical clearance). 3. **Trauma:** The most common cause of *acquired* lens dislocation overall is trauma, not systemic disease. 4. **Iridodonesis:** A clinical sign of ectopia lentis where the iris trembles upon eye movement due to lack of posterior support from the lens.

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