abnormal by HRT II analysis was 30% (Haymes et al., 2005).

SAP VF defects assessment: AGIS criteria

The AGIS used the HFA 24-2 TD printout to determine a patient’s VF score. In this study, if VF threshold values were depressed by 5–9 dB from the normal values, as measured in decibels, it was considered abnormal, depending on the field location. To qualify as abnormal, a depression had to be greater in the superior field than in the inferior field, and a depression had to be greater in the periphery than centrally.

Scores were assigned on the basis of the decibel depressions found in the various areas. A score of zero indicated no VF loss, while 20 was the maximum possible score. One stage of field loss progression was arbitrarily defined as an increase in score of four (The Advanced Glaucoma Intervention Study [AGIS]: 1, 1994).

A recent study showed a strong association between VF defects in the central 241 field and the risk of motor vehicle collisions (MVCs) among patients with glaucoma. In this study, as the AGIS score increased (VF defect was more severe) for both the better and worse eyes, there was a corresponding increase in the odds of an MVC (Hall and Owsley, 2005).

This finding means that the convention of assessing each eye’s field by itself, even just the central 241 field, may be informative with respect to crash risk. Thus, not only the binocular VF assessed by the Esterman grid methods or similar programs but also SAP VF assessment of each eye separately, as in the clinical routine, has to be considered by clinicians.

SAP VF defects assessment: CIGTS

The CIGTS used a scoring methodology similar to that used by the AGIS. Glaucoma staging in this study was also on the basis of the HFA 24-2 program, but the categories of probability values on the TD probability plot rather than decibel

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deviations as in AGIS were used. Scores were scaled from 0 to 20 (Musch et al., 1999).

Three of major glaucoma trials (AGIS, EMGT, and CIGTS), all using the same Humphrey VF tests, developed different criteria to define either VF damage or progression.

A recent study found that among progressing eyes, 58% were identified using AGIS criteria, 75% were identified with CIGTS criteria, and 96% were identified with EMGT criteria. The specificity for EMGT criteria was 89%, lower (Po0.05) than that of AGIS (98%) and CIGTS (99%) criteria (Heijl et al., 2008).

However, the prolonged test time of the original FT tests was tiring for patients, increasing the likelihood of fatigue artifact, which artificially depresses the threshold values of the test. Moreover, FT tests were time consuming and not practical in the clinical setting. These findings led to the development of new test strategies in order to shorten VF examination time. It is noteworthy that in the course of long-term clinical trials, key methods used to assess outcomes may become obsolete.

The authors of CIGTS evaluated the impact of converting from Humphrey 24-2 FT VF testing to SITA-standard (SS) VF testing during the followup phase of this clinical trial. They found that the CIGTS VF score and GHT results differed between SS and FT tests. Any change in the protocol used to identify a study’s primary VF outcome requires careful evaluation of converting from old test strategies to new ones (Musch et al., 2005).

Fastpac

The Fastpac strategy varies stimulus intensity in 3 dB steps depending on the patient response. Testing stops when the sequence crosses threshold, without inverting direction in smaller steps. In other words, threshold is recorded at the last seen stimulus intensity.

Since the Fastpac strategy measures threshold without the double crossing of threshold, sensitivity values determined by this algorithm show more intratest fluctuation. Nevertheless, shortening