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This report present further developments in a patient with an unusual vascular pattern on both optic nerve heads: the trunks of the central retinal vessels appear on the temporal side of the nerve head (situs inversus of the blood vessels of the nerve head). This vascular pattern was also present (to only slightly varying degrees) in all six of his children (two girls and four boys). Twenty-one years after the first presentation of this patient, he developed a non-secretory pituitary tumor. This case suggests that congenital nerve head anomalies may be markers for potential intracranial tumors later in life. INTRODUCTION Embryonic development of the pituitary gland and optic nerve head proceed within the same time-frame as development of the central nervous system (approximately 40 days after conception). The optic vesicle and stalk are outgrowths of the diencephalon, as is the neural portion of the pituitary gland (neurohypophysis). The anterior portion of the pituitary gland (adenohypophysis) and the anterior segment of the eye are derived from the surface ectoderm and neural crest. Thus, disturbances in growth occurring at around the 40-day stage may affect the development of both the optic nerve and the pituitary gland. In an ophthalmic context, the term situs inversus has been used to describe tilted nerve heads, a temporal appearance of the central retinal vessel trunks, or both. This condition can also be described in terms of the presence or absence of a crescent of visible sclera, usually on the side opposite the most elevated portion of the nerve head. This group of findings raises questions about the processes that are underway while these structures are being formed. Apple and co-workers1 described situs inversus of the retinal vessels as an element in the tilted disk syndrome; however, in the present cases, there were neither observable tilts to the nerve heads nor crescents of hypopigmentation. Thus, situs inversus of the retinal vessels may occur independently of the usually inferiorly located colobomas described by Apple, and may not be caused by disturbances in the closure of the fetal fissure. Situs inversus of the central retinal vessels is also seen in Williams (elfin-face) syndrome2 and Ehlers-Danlos syndrome.3 In some cases, tilted nerve heads by themselves are associated with visual field loss, and this is often of a bitemporal nature,4 without respect for the vertical midline. Considering that the axons from the nasal retina develop long before those from the temporal retina, the presence of bitemporal field losses argues for a disturbance >>>that occurs<<< comparatively early in the embryonic development of the visual system. T. David Williams, OD, MS, PhD Professor Emeritus School of Optometry University of Waterloo C A NA D I A N JO U R NA L o f O P T O M E T RY | R EV U E C A NA D I E N N E D ’O P T O M É T R I E VO L . 8 0 NO. 1 25

Pituitary Tumor Associated with Situs Inversus of the Optic Nerve Head