[Visual system function in patients after surgery for intracranial tumors]

Visual function was studied in patients after operations for brain tumours. The study group comprised 7 cases. Visual acuity, field of vision by kinetic and static methods and visual evoked potentials were studied before and after operations. The follow up time was from 1 to 51 months, mean 20 months. In all patients decreased visual acuity, visual field defects and VEP abnormalities were found, before operation. The first control examination after operation showed improvement of visual acuity in 2 cases after removal of pituitary tumours, and worsening of vision in all the remaining ones. In two cases of tumours spreading to the basis of the frontal lobe blindness of one eye developed. Static and kinetic perimetry showed in all cases enlarged visual field defects. VEP confirmed that removal of pituitary tumours compressing visual tract can improve vision: P100 amplitudes increased and latencies become shorter. Further VEP improvement occurred even 6-20 months after achieving of good visual acuity. No improvement of vision developed if the visual pathway had been damaged during the operation.

Pituitary tumours can be removed without damage to the surrounding structures and vision can improve after that. Meningiomas and gliomas lying in immediate vicinity of optic nerves and their chiasma or growing out from them are usually large and often their removal is associated with damage to the visual pathway leading to visual field defects to blindness. The assessment of vision should be based on static and kinetic perimetry and visual evoked potentials (VEP) since these methods are mutually complementary and only their comparison provides a full result.