Perimetry at the Bedside and Clinic

Abstract

While all of the visual field diagrams in this volume were obtained with a perimetric device, many of the defects they illustrate were detected on clinical examination. There are several reasons why it is worth developing the skill and confidence to probe for field defects with little more than the contents of one’ s pocket:

• 1 One does not always have immediate access to perimetric instruments. This is particularly the case in the emergency room and in most neurology clinics at present. In the urgent setting, one often has to make decisions about neuroimaging and other investigations before formal perimetry can be obtained.

• 2 Perimetry is reserved for selected patients. For patients not suspected of having a visual field defect, confrontation testing will be the only test of the visual field they will have. A good screening examination of the visual fields must be part of every routine neurologic or ophthalmologic examination. Because people are less attuned to their peripheral than central vision, such screening will occasionally uncover an asymptomatic peripheral field defect.

• 3 The choice of perimetric device and perimetric strategy should be guided by the suspicions aroused by the clinical examination and history. It is pointless to order automated perimetry of the central 24° of vision if one suspects a defect beyond 30°. A small defect within the central 10° of vision is better assessed by automated than Goldmann perimetry. Suspicion of a problem at the optic chiasm can guide the Goldmann perimetrist to concentrate testing around the vertical meridian.