Fig. 4. Electrodes for clinical electroretinography. A. Variety of electrodes and electrode types used for clinical electrophysiology of vision. Contact lens, foil, fiber, or skin electrodes may be used. Although the electrodes vary in their properties, all (except the skin electrodes) may provide roughly equivalent results. The largest variable in accounting for differences between electrodes is often the experience of the technician placing the electrodes. Several countries now require that electrodes be disposable, making foil and fiber electrodes favorable. B. A disposable contact lens electrode in use. C. A homemade fiber electrode in use. D. Use of a foil electrode.