Which congenital optic nerve anomaly is associated with a 'double-ring' sign?

• A. Optic nerve pit
• B. Morning glory syndrome
• C. Optic nerve hypoplasia
• D. Optic nerve coloboma

Answer: (C)

The key idea is recognizing how optic nerve hypoplasia presents on fundus exam. When the optic nerve is underdeveloped, the disc is unusually small and pale, and the surrounding peripapillary tissue often forms a notable crescent or rim. This combination can create two concentric rings around the optic nerve head—the inner pale disc and an outer ring of contrasting tissue—often described as a “double-ring” sign. This sign helps distinguish optic nerve hypoplasia from other congenital disc anomalies that have different appearances: optic nerve pits are crater-like depressions, morning glory syndrome shows a funnel-shaped disc with a central glial tuft, and optic nerve coloboma typically presents as an inferior notched defect. So, the double-ring sign is most characteristically linked to optic nerve hypoplasia.