Vision defects in patients with peri-chiasmal lesions

Patients with chiasmal lesions frequently suffer loss of vision, but some may be visually asymptomatic and have little, if any, visual field loss. This study addressed two questions about the nature of such loss: (1) which tests are best able to detect visual loss and (2) what is the relation between the size of a lesion and the degree and type of visual loss.

Visual acuity (VA), Goldmann perimetry, pattern evoked potentials, contrast sensitivity (CS), and color vision (CV) were assessed, in addition to a full ophthalmologic examination. Thirty-five patients were recruited from neurology, endocrinology, and ophthalmology departments; 31 had pituitary tumors and 4 had tumors of other origin (1 secondary) close to the chiasm. For analysis, patients were classified (1) according to whether they had visual symptoms on presentation and (2) according to lesion size.

Seventeen patients had visual symptoms; all had visual field defects and all but one had two or more additional abnormal test results. Of the 18 visually asymptomatic patients, 12 had visual field defects and 14 had at least 2 abnormal test results; 7 had tumors with less than 5 mm of suprasellar extension, of whom 5 had field loss or at least 2 abnormal test results. CS was abnormal most often (85% of patients), followed by Goldmann perimetry (80%), visual evoked potentials (VEPs) (57%), CV (49%), and VA (26%).

Our results support previous reports that asymptomatic patients and those with intrasellar tumors or only small amounts of suprasellar extension may have demonstrable visual dysfunction. Perimetry did not appear to be significantly worse than other more recently developed tests, which have often been regarded as being more sensitive, for detecting vision loss. However, VA and clinical observation of pupil reactions had poor sensitivity.