Chiasmal pathology causing inability to access information in the temporal visual field

Abstract

Background: A series of four patients with evidence of chiasmal pathology were found to be unable to access information in the temporal visual field. Only the optotypes in the nasal field were seen during monocular testing of acuity; the letters in the temporal visual field remained unseen. Moreover, the process of reading was found to be significantly impaired in three of the four patients. Methods: Conventional distance visual acuity testing and visual field assessments were carried out. Three patients had undergone surgery for tumor adjacent to the optic chiasm (one craniopharyngioma and two suprasellar pituitary adenomas). One patient had sustained permanent minute paracentral bitemporal scotomata after head injury. Results and conclusions: In each case, only printed material in the nasal visual field was observed by the patients during monocular viewing even though there was no restriction of horizontal eye movements.This defective visual behavior affected both eyes in three patients and was unilateral in one.The disturbance was reversible after surgery for pituitary adenoma in one case, but was longstanding in three. It is hypothesized that the defective visual behavior is related to an associated cognitive lack of spatial awareness and compensation for the visual field defect possibly due to a disturbance of visual reflex search mechanisms. Recognition of the specific visual behavior in patients during routine eye examination should arouse diagnostic attention to lesions of the chiasm.