Question:medium
Bilateral inferior dislocation of the lens (ectopia lentis) is characteristically seen in which condition?
Bilateral inferior dislocation of the lens (ectopia lentis) is characteristically seen in which condition?
Show Hint
Direction matters: down and in is metabolic, up and out is connective tissue.
Updated On: Jun 24, 2026
- Marfan's syndrome
- Homocystinuria
- Weil-Marchesani syndrome
- Trauma
Show Solution
The Correct Option is B
Solution and Explanation
Step 1: The key to this question is the DIRECTION of lens displacement, since several inherited disorders produce ectopia lentis but each in a typical direction.
Step 2: Homocystinuria is an autosomal recessive defect of methionine metabolism (cystathionine beta-synthase deficiency). The weakened zonules give way inferiorly, so the lens drifts down and toward the nose on both sides, producing bilateral inferior (inferonasal) ectopia lentis.
Step 3: Contrast this with Marfan's syndrome, where the displacement is superotemporal (up and out), and with Weil-Marchesani syndrome, where a small spherical lens tends to fall forward into the anterior chamber. Traumatic dislocation is one-sided and follows the line of injury, not a tidy bilateral inferior pattern.
Step 4: Therefore a symmetric, bilateral, downward lens dislocation maps to homocystinuria.
\[\boxed{\text{Homocystinuria}}\]
Step 2: Homocystinuria is an autosomal recessive defect of methionine metabolism (cystathionine beta-synthase deficiency). The weakened zonules give way inferiorly, so the lens drifts down and toward the nose on both sides, producing bilateral inferior (inferonasal) ectopia lentis.
Step 3: Contrast this with Marfan's syndrome, where the displacement is superotemporal (up and out), and with Weil-Marchesani syndrome, where a small spherical lens tends to fall forward into the anterior chamber. Traumatic dislocation is one-sided and follows the line of injury, not a tidy bilateral inferior pattern.
Step 4: Therefore a symmetric, bilateral, downward lens dislocation maps to homocystinuria.
\[\boxed{\text{Homocystinuria}}\]
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