Congenital tumours in the anterior visual system with dysplasia of the optic discs

SUMMARY The occurrence of dysplastic optic discs in young patients with tumours involving the anterior visual pathway not only may provide a valuable diagnostic sign but also bears witness to the early prenatal origin of these tumours. An optic disc may be considered to be dysplastic when it is congenitally abnormal owing to a developmental abnormality. Gross anomalies include colobomata and pits, and the optic disc may be of abnormal size, an unusual shape, or have an abnormal vascular arrangement. Minor developmental anomalies in-clude unusual pigmentation or abnormalities of the peripapillary retina. Small dysplastic or hypoplastic discs may be difficult to diagnose, since there are no absolute criteria and no readily available techniques for measurement. Clinical judgment can be enhanced by evaluation of the ratio between the apparent size of the disc and the retinal arterioles or the size of a disc relative to the size of the fundus in a standard fundus photograph, but even with these techniques the vagaries of observation leave the diagnosis to the clinician alone. Anomalies of the outline and vascula-ture have to be obvious to be considered abnormal, but there are no definitive criteria. The incidence of congenital optic disc anomalies in the population is impossible to assess, but Duke-Elder ' considered them to be rare in their gross forms, and Riise2 esti-mated that a common type of optic disc anomaly, the inferonasal conus, occurs in 1 % of the population. Congenitally abnormal optic discs have been reported with bitemporal visual field defects, unassociated with disease of the nervous system,25 suggesting a concomitant chiasmal anomaly. Anomalous optic discs in patients with suprasellar tumours have been considered2467 to be an incidental association. These authors reported 6 cases, and of the 2 patients in whom the pathology was recorded one had a dysgerminoma and clearly congenitall