Automated achromatic contrast and chromatic discrimination sensitivity testing in dysthyroid optic neuropathy

Our experience of patients with dysthyroid eye disease shows that normal chromatic discrimination sensitivity precludes the diagnosis of optic nerve compression (31 patients), and that clinically confirmed optic nerve compression is invariably associated with decreased chromatic discrimination sensitivity thresholds (8 patients). Dysthyroid patients enrolled in this study underwent automated achromatic contrast and chromatic discrimination sensitivity testing on presentation, with repeat assessment of those patients suspected of developing optic nerve compression. If chromatic discrimination sensitivity was decreased, patients were followed up more frequently. If abnormal chromatic discrimination sensitivity was accompanied by a relative afferent pupillary defect (RAPD) or decreased Snellen visual activity (VA), then optic nerve decompression was performed. The automated chromatic discrimination sensitivity test described represents a quick, reproducible and cheap clinical test which we feel is of value in assessing patients with dysthyroid eye disease. We suggest that sequential chromatic discrimination sensitivity assessment is a sensitive and effective way of monitoring patients at risk of dysthyroid optic neuropathy.