Humphrey Field Analysers

Humphrey Field Analysers are generally very well designed and built but are more costly than their competitors. They are popular with hospital clinics and are regarded as the gold standard for visual field analysis.

There are 2 main types

• Bowl Perimeter 500 series and 700 series and FDT Frequency Doubling Technique
• Bowl Perimeter types

The Humphrey Bowl Perimeter types of field analyzer differ fundamentally to other makes in that they do not use LED’s as stimulus points. The Humphrey Field Analyzer is basically a computer operated and motorised version of the Goldmann Perimeter which uses a single lamp for illumination and filters to adjust the stimulus size and intensity and a complex mirror system which directs the position of the stimulus point. This system has the advantage that it is extremely versatile in the positioning, size and intensity of the stimulus points but makes it impossible to incorporate multiple stimulus points.

COMMON PROBLEMS

1. User screen too dim even on full brightness
2. Motorised chin rest mechanism failure

FDT Frequency Doubling Technique

The FDT is a 20 degree field screener which uses frequency doubling technique. The patient looks into a tube towards a CRT screen which produces interference patterns. These patterns are more difficult to see if the patient is suffering from the first stages of field loss and theoretically can detect abnormalities earlier than a conventional light stimulus instrument.

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