The electro-oculogram (EOG) is considered to
reflect the integrity of the pigment epithelium and
adjacent photoreceptors of the eye.' The EOG is
conventionally derived by having a patient alternately
fixate targets placed to the right and left during dark
and light adaptation. The potential is measured differentially
from electrodes placed on each side of the
bony orbit during stereotyped horizontal eye movements.
The size of this potential is related directly to
the magnitude of the corneoretinal potential.
2Individuals with large central scotomas, patients with
very small residual central visual fields, and subjects
unable or unwilling voluntarily to produce standardised
eye movements may present obstacles to the
recording of the EOG by standard techniques.