Visual Fields: Visual Field Test Strategies

Core Messages

››Standard Automated Perimetry (SAP) using an adaptive forecasting threshold strategy for the central visual field remains the preferred visual field testing method for glaucoma.

››Most glaucoma clinics use adaptive forecasting threshold test procedures (SITA, ZEST, TOP, GATE) as methods for visual field screening, while FDT screening can provide a rapid, accurate, and reliable screening method for general ophthalmic practices.

››Specialized testing (SWAP, FDT, Rarebit, mfVEP, motion, flicker) may improve the ability to detect and monitor glaucomatous visual field loss in equivocal or borderline cases.

››Options exist for visual field testing of inattentive and uncooperative patients.

15.1  What Are the Basic Differences

Between Different Visual Field

Machines and Tests?

15.1.1  Automated vs. Manual

The question can be answered in many ways. First of all, there are visual field devices used to perform automated

C. A. Johnson

Department of Ophthalmology and Visual Sciences, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA 52242-1091, USA

e-mail: chris-a-johnson@uiowa.edu

static perimetry and those for manual kinetic perimetry. Automated tests utilize computer programs to vary test speed, target size, and luminance. Automated tests also benefit from standardized testing conditions, which can be used to interpret results across machines, and efficient testing strategies (more on these later). They present light stimuli of varying luminance to the patient in specific locations for a given duration of time before the next stimulus is presented (0 dB is a maximal stimulus intensity, 10 dB is 1-log unit lower than the maximum, 20 dB is 2 log-units lower, etc). Automated devices provide results that can be directly compared to ageadjusted normative values, which have been derived from testing hundreds of normal subjects. Commonly used automated perimeters are the Humphrey visual field analyzer (HFA) (Zeiss, Inc., Dublin, CA) and the Octopus perimeter (Interzeag/Haag Streit, Koeniz, Switzerland). Manual perimeters require a skilled examiner to present targets to the patient. Both static and kinetic testing can be performed manually. In kinetic testing, a moving target of varying size and luminance is presented to the patient. Manual kinetic perimetry is more flexible and interactive for the patient, and it provides the opportunity to evaluate the far peripheral visual field [1]. Also in existence is a semi-automated kinetic perimetry program on the Octopus perimeter in which a computer program performs kinetic perimetry.

15.1.2  Threshold vs. Forecasting/ Adaptive Strategies

The main differences among automated devices are related to the specific attributes of their threshold estimation strategies and test location patterns. Threshold testing quantifies visual sensitivity and involves determining