Integrity of the optic nerve is tested by except :

Electroretinography (ERG) measures the electrical response of the retina to flashes of light, the flash electroretinogram, or to a reversing checkerboard stimulus, the pattern ERG (PERG).All other test in the option tests the integrity of optic nerve. Perimetry or Tangent Screen examination is used to examine the central and peripheral visual fields. Usually performed separately for each eye, it assesses the combined function of the retina, the optic nerve, and the intracranial visual pathway. The visual evoked response (VER) measures the electrical potential resulting from a visual stimulus. However, because it is measured by scalp electrodes placed over the occipital coex, the entire visual pathway from retina to coex must be intact in order to produce a normal electrical waveform reading. Ref : Chang D.F. (2011). Chapter 2. Ophthalmologic Examination. In P. Riordan-Eva, E.T. Cunningham, Jr. (Eds), Vaughan & Asbury's General Ophthalmology, 18e.