Abstract: The invention administers an objective clinical test to an eye that measures the visual sensitivity of the superior retina and the inferior retina, by alternately presenting a stimulus pair comprising a shaped superior light stimulus and a shaped inferior light stimulus that are horizontal mirror images of one another and have shapes encompassing visual field defects. The shaped superior and inferior light stimuli stimulate pupillary responses whose amplitudes are measured. A cycle-averaged pupillary response balance and a luminance ratio are computed for each presentation of a stimulus pair. A stimulus pair response curve is computed by fitting cycle-averaged pupillary response balances to a sigmoid function of the luminance ratios. A balanced luminance ratio at which the cycle-averaged pupillary response balance is equal to about zero is computed from the sigmoid function. The balanced luminance ratio is indicative of the presence and location of retinal nerve damage.