**Ectopia Lentis and Associated Conditions**

**Core Concept**
Ectopia lentis refers to the displacement or malposition of the crystalline lens in the eye. This condition can result from various causes, including genetic disorders, trauma, and systemic diseases that affect the lens or the surrounding structures.

**Why the Correct Answer is Right**
Ectopia lentis can be associated with several conditions, including Marfan syndrome, Weil-Marchesani syndrome, and homocystinuria. These conditions often involve defects in the fibrillin-1 gene, which plays a crucial role in the formation of elastic fibers in the eye. The lens is displaced due to the weakness of the suspensory ligaments, such as Zinn's ligaments or the ciliary zonules. The correct answer will be one of the conditions that is not typically associated with ectopia lentis.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because homocystinuria is indeed associated with ectopia lentis. Elevated levels of homocysteine in the blood can lead to defects in the lens capsule and the suspension ligaments, causing lens displacement.

**Option B:** This option is incorrect because Weil-Marchesani syndrome is a recognized cause of ectopia lentis. The condition is characterized by short stature, brachydactyly, and characteristic eye features, including lens displacement.

**Option C:** This option is incorrect because Marfan syndrome is a well-documented cause of ectopia lentis. The condition is caused by mutations in the fibrillin-1 gene and affects the formation of elastic fibers, leading to lens displacement.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that ectopia lentis can be a sign of an underlying systemic disease, and a thorough evaluation is essential to identify the underlying cause.

**Correct Answer:** D