Driving after epilepsy surgery: effects of visual field defects and epilepsy control

The aim of this study was to assess the eligibility to drive in patients with mesial temporal sclerosis who undergo anterior temporal lobectomy. The two major determinants in a patient's ability to drive after such surgery are visual field defects and their seizure frequency. Thirteen patients were selected. The postoperative seizure frequency was assessed using Engel's criteria. Automated static perimetry was performed which consisted of a Humphrey Field Analyser (HFA) 30-2 Test, one for each eye and a Binocular Esterman 120 Test. Seven out of the 13(54%) selected patients had no seizures post-operatively (Engel's 1); three (23%) patients had less than two seizures per year (Engel's 2) and three (23%) had more than 90% improvement in the frequency of seizures (Engel's 3). The seven patients with no seizures postoperatively were eligible to apply for a driving licence. Automated static perimetry performed on the same patients revealed three (23%) had normal visual field or non-specific loss, seven (54%) had partial homonymous quadrantanopia, one (8%) had complete homonymous quadrantanopia and two (15%) had bilateral concentric loss attributable to vigabatrin, which may have masked any loss occurring due to surgery. Of the 13 patients, only seven ( 54%) passed the standardised DVLA Esterman visual field test. Of the six (46%) who failed DVLA Esterman visual field test, one had complete homonymous quadrantanopia, three had incomplete homonymous quadrantanopia and two had concentric loss (due to vigabatrin). Although seven (54%) patients passed the visual field test and seven (54%) patients were seizure free only five of the seven seizure-free patients (i.e. 38% of the total number of patients) had visual fields that would make them eligible to drive. As driving is now stated by patients(1) as a major factor that improves their quality of life, it is important to stress the significance of surgically induced or other iatrogenic visual field defects that may prevent them from driving prior to the operation to avoid disappointments afterwards.