A recent study that sampled the performance of nonphysician perimetrists in community ophthalmic practices revealed that the detection rate for any defect averaged only 69%. Nasal steps were correctly identified more often (77%) than were hemianopic defects (44%). If this relatively low identification rate for hemianopias is representative, then patients with unexplained visual loss should all have CT scans regardless of the result of the visual field examination. Greater accuracy in perimetry may be achieved by improved teaching, by optimizing exploration strategies, and perhaps by automated devices.