Patients with prior optic neuritis were examined for the presence of an unilaterally impaired pupillary response to light by a method which is believed to be superior to conventional testing of pupillary constriction. A positive pupil sign was found in ten eyes with 20/20-2 or better vision. The clinical sensitivity of the test is highlighted since conventional tests of pupillary light constriction did not reveal a pupilmotor deficit. Each of the patients showing a positive swinging flashlight test had mild unilateral optic nerve pallor. The results further indicate that in mild optic nerve damage, a positive swinging flashlight test is more consistently present than a color vision deficit or a demonstrable visual field scotoma.
Stanley JA, Baise GR. The Swinging Flashlight Test to Detect Minimal Optic Neuropathy. Arch Ophthalmol. 1968;80(6):769-771. doi:10.1001/archopht.1968.00980050771016