Many eye care practitioners would agree that glaucoma is difficult to confidently diagnose in a single visit. Open angle glaucoma usually presents as a symptomless condition and manifests itself gradually.

The doctor must combine several tests including history, visual fields, intraocular pressure, gonioscopy, optic nerve head analysis and nerve fiber layer analysis to make the correct diagnosis. Sometimes a patient is followed for years before a decision to treat is made.

Conversely, a patient may present for the first time with extensive vision loss that should have been prevented long ago. Along with glaucoma, many other ocular diseases can lead to visual field loss. The main goal of the practitioner is to preserve as much of the patient's visual field for the rest of his or her life.As such, one of the key tests to this goal is visual field testing, or perimetry.

Early visual field tests conducted over a century ago were based mainly on kinetic stimulus presentation ­ that is, a response to a moving peripheral stimulus was made while the patient looked straight ahead at a stationary fixation point.

The classic Tangent Screen and Goldmann Bowl Perimeter are good examples and are still used today in certain practice situations. Other variations on the kinetic perimeters include the arc and auto tangent screen perimeters.

This has resulted in highly quantifiable, sensitive visual field results. Newer test algorithms have resulted in testing strategies such as:

SWAP (Short Wavelength Automated Perimetry)

or "blue-on-yellow" perimetry (Humphrey) ­ This method presents blue static stimuli on a uniform yellow background, intended to test a smaller population of retinal neurons that selectively respond to those color wavelengths.

The test is thought to potentially reveal visual field loss 5-6 years ahead of traditional white-on-white automated perimetry, but it requires a significantly longer testing time.

FASTPAC, SITA (Swedish Interactive Testing Algorithm)

Standard, SITA Fast (Humphrey) ­ These tests use "intelligent" analysis of the patient's responses and age-normed statistical data to significantly shorten the testing time. There may be some limitations in terms of analysis of field loss progression, as well as limitations on the number of missed point re-tests, but statistical correlation with traditional threshold testing is good.

Kinetic Fixation Perimetry (Dicon)

A feature unique to these perimeters is that the patient is constantly looking at a moving fixation target during testing, which has been found to make the visual field testing more comfortable for the patient.

Multiple Stimulus Presentation (Dicon)

One to four stimuli are presented at a time, requiring the patient to respond one to four times, respectively. Meant to speed the visual field testing, it is not used regularly for most patients.

Examples of some contemporary automated visual field analyzers.


From left to right: Dicon Autoperimeter, Oculus Easyfield, Zeiss-Humphrey Field Analyzer II

Understanding Frequency Doubling Perimetry

A Practical Approach

 Lorne Yudcovitch, O.D., M.S., F.A.A.O.

Goldmann Bowl Perimeter Shown on Left; Illustration of Goldmann Testing Shown on Right

As computerized, automated visual field testing became more popular, various companies such as Zeiss-Humphrey, Dicon, Synemed, Medmont, Oculus, Kowa Optimed, and InterZeag utilized static "white-on-white" stimulus presentations (e.g., a white light of various intensities is flash-presented in numerous areas on a uniform white background).

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