Optic Disk Coloboma (Morning Glory Disk)
An optic disk coloboma (Fig. 13.18) is the result of incomplete closure of the embryonic optic cup. The optic disk is enlarged with a funnel-shaped depres-sion with whitish tissue and a peripapillary pigment ring. The retinal vessels extend outward across the margin of the disk in a radial pattern without a central trunk vessel. Patients with optic disk coloboma often have decreasedvisual acuity and visual field defects.