**Core Concept**
Ectopia lentis refers to the displacement or malposition of the lens in the eye, which can result from various underlying conditions affecting the lens capsule, zonular fibers, or the lens itself. This condition can lead to vision problems and is often associated with systemic diseases.

**Why the Correct Answer is Right**
Ectopia lentis is commonly seen in Marfan syndrome, a genetic disorder that affects the connective tissue in the body. The condition is caused by mutations in the FBN1 gene, which codes for fibrillin-1, a protein essential for the formation of elastic fibers in connective tissue. In Marfan syndrome, the weakened zonular fibers supporting the lens lead to its displacement. Other conditions, such as trauma, congenital anomalies, and certain systemic diseases like homocystinuria, can also cause ectopia lentis.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because while diabetes can cause cataracts, it is not a primary cause of ectopia lentis.
**Option B:** This option is incorrect because while trauma can cause lens dislocation, it is not a systemic condition that leads to ectopia lentis.
**Option C:** This option is incorrect because while certain medications can cause cataracts, they are not typically associated with ectopia lentis.

**Clinical Pearl / High-Yield Fact**
In patients with ectopia lentis, it is essential to investigate for underlying systemic conditions, such as Marfan syndrome, as these conditions can have significant implications for the patient's overall health and require timely management.

**Correct Answer: C. Marfan syndrome**