THE NERVE FIBER ANALYZER

Abstract

The Nerve Fiber Analyzer (NFA; Laser Diagnostic Technologies, San Diego, CA) is a scanning laser polarimeter that was developed to measure the thickness of the human retinal nerve fiber layer (NFL) in vivo. Because glaucoma is associated with thinning of the NFL, the instrument potentially could be used for the detection and follow-up of glaucoma. The NFA came onto the market in 1993, and has been upgraded several times since then. The first results were promising but not altogether satisfactory, partly because the reproducibility of measurements was poor and very operatordependent. The authors were able to improve the reproducibility of measurements of the first version of the in~trument.’~ A sensitivity and specificity for detecting glaucoma was established that was unrivalled by any other single technique.25 The first version of the instrument was followed by the NFA I1 and later by the NFA GDx (or GDx), which both represented large revisions in hardware and software. Some of these revisions have further improved the reproducibility of measurements. The GDx version contains a large normative database and a statistical software package that allow comparison of an individual’s data with those of age-matched normal subjects of the same ethnic origin. An individual’s data may be stored for future reference to