Congenital pits of the optic nerve head result from an imperfect closure of the superior edge of the embryonic fissure. An unequal growth on both sides causes a delayed closure of the fissure at approximately 5 weeks of gestation. Optic pits appear as crater-like indentations of the surface of the optic nerve head usually with a steep temporal wall.¹

Anatomically the most anterior component of the optic nerve head contains the retinal nerve fibre layer (RNFL), composed of approximately 1.2 million unmyelinised retinal ganglion cell axons extending from all regions of the retina. The outgrowth of axons from certain ganglion cells may be incomplete so that the primitive epithelial papilla is built up with aberrant nerve fibres.² Histological sections of optic pits define defects in the lamina cribrosa associated with rudimentary retinal tissue, resembling pigmented tissue and aberrant nerve fibres. These anomalous papillomacular nerve fibre bundles may be less resistant,¹ predisposing this sector to spontaneous schisis-like retinal detachments during later life.³

We present a young patient with a unilateral optic pit and a clinically significant temporal nerve fibre loss. In vivo measurements by optical coherent tomography (OCT) determined the thickness of RNFL at the side …