Figure 1. Description of the ERG apparatus and flash unit.

A, the mouse was anaesthetized with 1.5% isoflurane delivered through a tube fitting snugly around its nose and held on an adjustable, heated platform. Light from a xenon flash unit was delivered to the eye by a 5 mm diameter fibre optic positioned ∼1 mm from the corneal surface and normal to its centre of curvature. ERGs are recorded via a differential amplifier connected to a platinum ring corneal electrode and a reference electrode inserted subcutaneously into the forehead (Methods). B, spectral profiles of light delivered through the glass fibre optic bundle (black trace) and a liquid guide (red trace), measured with an Ocean Optics Inc (830 Douglas Ave, Dunedin, FL 34698) USB 2000 spectrometer with 0.3 nm resolution. C, the time course of the flash measured with Thorlabs Inc (56 Sparta Ave, Newton, NJ 07860) FDS010 photodiode with 1 ns rise time.