Brightness-sense and optic nerve disease.

We describe a simple device used to compare the sense of brightness in the two eyes. An investigation of brightness-sense with this device in normal persons and patients with optic nerve disease, maculopathies, cataract, and factitious visual impairment shows that brightness testing can provide useful information supplementary and complementary to conventional clinical and laboratory investigations. Impairment of brightness-sense was a consistent finding among patients with optic neuropathies and, in some cases, brightness testing appeared to be more sensitive than other techniques in establishing the presence of disease. Brightness-sense was also used to monitor the course of the patient's illness. Abnormalities were also found among some patients with unilateral maculopathies, but significant intereye differences in brightness-sense were not encountered among normal persons or patients with cataracts. Patients with factitious visual loss gave variable responses, and the nature of their disorder could be identified by the inconsistency of their responses.