A practical approach to measuring the visual field component of fitness to drive

Aims: To determine the level of agreement between merged monocular visual field tests (the integrated visual field) and the binocular Esterman visual field test in classifying patients' visual status for UK legal fitness to drive. To examine the link between these two tests and the useful field of view (UFOV) test, a test which is considered to be a surrogate for the visual capability for safe driving. Methods: Primary open angle glaucoma patients with bilateral overlapping visual field defects were recruited prospectively. Patients performed the bilateral monocular field tests (to generate the integrated visual field), the Esterman test and the UFOV test on the same visit. Patients were classified as "pass'' or "fail'' by both the integrated visual field and the Esterman test. UFOV risk scores were calculated for each patient. Results: 65 patients were recruited. Substantial agreement was found between the integrated visual field and the Esterman test in classifying patients as "pass'' or "fail'' (kappa = 0.69). No patients classified as "pass'' by the integrated visual field test were classified as "fail'' by the Esterman test. Eight patients who were classified as "pass'' by the Esterman test were classified as "fail'' by the integrated visual field test. The UFOV risk characteristics of these eight patients suggested they were more similar to those of the 13 patients who were classified as "fail'' by both the tests, than the 44 patients who were classified as "pass'' by both tests. Conclusions: The integrated visual field test agrees well with the current method (Esterman) of classifying visual fields with regard to legal fitness to drive in the United Kingdom in patients with glaucoma; it appears superior to the current method in identifying those with reduced fitness to drive as measured by the UFOV. The integrated visual field test could perform a valuable screening or diagnostic role in the assessment of glaucoma patients' fitness to drive.