**Core Concept**
Dislocation of the lens, also known as ectopia lentis, is a condition where the lens of the eye is displaced from its normal position. This can be caused by various factors, including trauma, congenital conditions, and systemic diseases that affect the connective tissue or the lens itself.

**Why the Correct Answer is Right**
Homocystinuria is a genetic disorder characterized by the accumulation of homocysteine in the body due to enzyme deficiencies. One of the key features of homocystinuria is the dislocation of the lens, which occurs due to the weakening of the suspensory ligaments (zonules) that hold the lens in place. This is because homocysteine interferes with the cross-linking of collagen, a critical component of the zonules. As a result, the lens becomes loose and can dislocate anteriorly or posteriorly, leading to vision problems.

**Why Each Wrong Option is Incorrect**
**Option A:** Trachoma is a bacterial infection of the eye that causes inflammation and scarring of the conjunctiva, but it is not associated with lens dislocation.
**Option B:** Diabetes mellitus can cause cataracts, but it is not typically associated with lens dislocation.
**Option D:** Turner's syndrome is a genetic disorder that affects females, characterized by short stature, ovarian dysgenesis, and other systemic features, but it is not typically associated with lens dislocation.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that lens dislocation can be a feature of various systemic diseases, including Marfan syndrome, Ehlers-Danlos syndrome, and osteogenesis imperfecta, in addition to homocystinuria. A high index of suspicion and thorough systemic evaluation are necessary to diagnose the underlying cause of lens dislocation.

**✓ Correct Answer: C. Homocystinuria**