What is the most common location of an optic nerve coloboma?

What is the most common location of an optic nerve coloboma?

• A. Inferior/temporal
• B. Inferior/nasal
• C. Superior/nasal
• D. Superior/temporal

Answer: (B)

Optic nerve coloboma arises from failure of closure of the embryonic fissure, which leaves a notch in the developing optic nerve. This fissure runs along the inferior-nasal edge as the eye forms, so when closure fails the resulting defect most commonly sits in the inferior and nasal part of the optic disc. That inferior-nasal location is the classic pattern seen clinically. Other quadrants can be involved, but they’re much less typical because the closure pattern of the fissure makes defects there far rarer.

Optic nerve coloboma arises from failure of closure of the embryonic fissure, which leaves a notch in the developing optic nerve. This fissure runs along the inferior-nasal edge as the eye forms, so when closure fails the resulting defect most commonly sits in the inferior and nasal part of the optic disc. That inferior-nasal location is the classic pattern seen clinically. Other quadrants can be involved, but they’re much less typical because the closure pattern of the fissure makes defects there far rarer.