The measurement of visual field defects for the purposes of assessing medical fitness to drive commonly employs the use of the Esterman visual field test. The present study aimed to determine the level of agreement between the measured visual fields when using the binocular Esterman test and when using the Integrated Visual Field test (IVF), a newly developed measurement technique using merged bilateral monocular visual fields. The agreement between the results of the two tests was judged in relation to classifying patients’ visual status for UK legal fitness to drive. The study also aimed to examine the link between performance of these two tests and a safe driving by assessing the association between visual field defect measurements obtained using each method and the performance on the Useful Field of View (UFOV), which is considered to be a surrogate for the visual capability for safe driving. Primary open-angle glaucoma patients with bilateral overlapping visual field defects were recruited prospectively from clinics at Moorfields Eye Hospital during the period from March 2002 to July 2003. Patients performed the bilateral monocular field tests (needed to generate the IVF), 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, using the current medical standards required to hold a UK driving licence. UFOV risk scores were calculated for each patient. Sixty-five patients were recruited. The mean age of the patients at examination was 69.3 years (range 30 to 85 years). Substantial agreement was found between the integrated visual field and the Esterman test in classifying patients as ‘pass’ or ‘fail’ (kappa ¼ 0.69). No patients classified as ‘pass’ by IVF were classified as ‘fail’ by the Esterman test. Eight patients who were classified as ‘pass’ by the Esterman test were classified as ‘fail’ by IVF. None of these eight were in the UFOV ‘low risk’ or ‘no risk’ categories. Their UFOV characteristics were significantly different from those of the 44 patients who were classified as ‘pass’ by both the IVF and the Esterman test, but were very similar to those of the 13 patients who were classified as ‘fail’ by both techniques. This study shows that Integrated Visual Field test agrees well with the current method (the Esterman test) of classifying visual fields with regard to legal fitness to drive in the UK. The IVF appears superior to the current method in identifying those with reduced fitness to drive as measured by the Useful Field of View. Therefore, the Integrated Visual Field test could perform a valuable screening or diagnostic role in the assessment of glaucoma patients’ fitness to drive. (Author/publisher)
Abstract