To find out the most sensitive parameter of early toxic ocular changes, a group of patients was extensively examined at regular intervals during therapy with ethambutol. Colour vision abnormalities could be detected using the desaturated panel of Lanthony in the presence of normal visual acuity, normal visual fields, normal visual-evoked potentials and a normal panel D-15 test. Maj or blue-yellow errors were found in treated patients without visual complaints as well as in a group of healthy volunteers, but there was a significant difference between both groups. In a later stage of intoxication, blue defects, red-green defects or tritanomalous defects can be observed, together with other symptoms of ocular intoxication.

Since delayed pattern evoked potentials (EPs) are a sensitive symptom of demyelination or compression of the optic nerve, a group of 33 patients with endocrine orbitopathy were examined in order to see whether or not, in this disease too, damage to the optic nerve could be detected at an early stage. Below a visual acuity of 0.4, all patients had delayed responses. Most interesting was the group of patients with normal visual acuity and delayed responses. Before conclusions can be drawn this group will have to be enlarged and followed up.

(Br J Ophthalmol 1997;81:291-294)