Isolated coloboma of the optic nerve head: an echographic evaluation.

The echographic profile of the optic nerve was studied in ten eyes with coloboma of the optic nerve head. Optic nerve dimensions measured with A-scan ultrasonography revealed an increase in the overall diameter of the nerve; B-scan echography was performed in six patients and showed excavation of the optic discs with a double-walled lining posteriorly. Additional B-scan features included widening of the anterior angle of the nerve and random perpendicular echoes in the anterior part of the nerve head. The similarities and differences in echographic pictures observed in coloboma of the optic disc and glaucomatous optic atrophy are described, and the genesis of these ultrasonographic features is discussed.