Fig. 9. A cupola used for Ganzfeld stimulation. Full-field or Ganzfeld stimulation is important to provide uniform illumination of the entire retina. Although a translucent corneal contact lens may be used, it is more common to use a cupola. A. Cupola manufactured by LKC Technologies (Gaithersburg, MD; http://www.lkc.com). A typical cupola has a method to control background luminance and flash intensity (possibly wavelength). The LKC cupola also has three light-emitting diodes (LEDs) (only two can be seen). The central one is for fixation in electroretinograms and flash visually evoked potentials. The two lateral LEDs are separated by 30 degrees and are used to control eye movements during electro-oculography. B. Adult seated with her chin on the chin rest. Note the active electrodes are Burian-Allen electrodes. The reference skin electrode is on the ipsilateral earlobe and the ground electrode on the forehead. C. Child with her chin on the chin rest. Note the active electrodes are skin electrodes placed on the lower lid. The reference skin electrode is near the ipsilateral outer canthus and the ground electrode on the forehead.