A comparison of diagnostic protocols for interpretation of frequency doubling perimetry visual fields in glaucoma

BACKGROUND: Frequency doubling perimetry (FDP) shows good correlation with achromatic automated perimetry in the assessment of glaucoma. However, many recommended protocols lead to a significant number of false positives and negatives. Therefore, it may be difficult to identify visual field loss owing to glaucoma. We investigated the accuracy of a diagnostic protocol that only considered either temporal wedge, arcuate, or nasal step field loss on an FDP field as significant. METHODS: Sixty-eight subjects who were glaucoma suspects, glaucoma patients or normal controls were recruited selectively. After achromatic automated perimetry and FDP visual field testing, results were compared between a conventional protocol and ones that took into account the position of FDP visual field loss. RESULTS: If an FDP field was considered abnormal only when either a temporal wedge, an arcuate or a nasal step defect was present, the presence of a nasal step yielded the most accurate results with the least false positives (κ coefficient=0.76) and with only minimal increase in false negatives, compared with a conventional FDP protocol (κ coefficient=0.70). CONCLUSIONS: Although, not statistically significant in this case, our results suggested a trend that a diagnostic protocol which considers nasal step FDP field loss significant may have a greater degree of accuracy when compared with conventional protocols and may facilitate interpretation in a clinical setting.