Can the specificity of the FDT for glaucoma be improved by confirming abnormal results?

Purpose: To determine whether the specificity of the frequency-doubling tec hnology (FDT) perimeter in the screening mode for glaucoma can be improved by repeating abnormal screening results. Methods: The FDT perimeter was used in C-20-5 screening mode, and the right eye was tested first. After both eyes were tested, the screening was repea ted in eyes with any abnormal visual field defects on FDT perimetry. The pr intouts were categorized as possible visual field abnormality (zero or one miss), probable visual field abnormality (two to four misses), and definite visual field abnormality (more than five misses). A clinical ophthalmologi c examination was conducted on the day of the FDT perimetry screening. Results: Complete data were available far 223 people. The participants rang ed in age from 23 to 91 years (mean, 68.5 years; standard deviation, 13.7 y ears), and 119 (53%) were women. The sensitivity of the FDT perimetry scree ning was 100%; both cases of glaucoma showed an abnormality on FDT perimetr y both times. The specificity improved moderately from the first screening to the second screening. The specificity the first time was 62% (95% confid ence interval, 53.1-71.2). The specificity the second time was 68.5% (95% c onfidence interval, 59.8-77.1). Improvement on FDT perimetry rescreening va ried by the language spoken at home. Seven of the 19 non-English speakers w ithout glaucoma improved on rescreening, compared with none of the 23 Engli sh speakers (P = 0.002). Seven of the 25 right eyes with FDT perimetry abno rmalities both times and no glaucoma had no other detectable diseases. Thre e of 24 left eyes with FDT perimetry abnormalities both times and no glauco ma had no other detectable diseases. Of the 85 patients who did not have gl aucoma but had FDT perimetry abnormalities both times, only one did not hav e some other detectable disease. Discussion: In summary, the sensitivity for glaucoma of the C-20-5 screenin g mode is excellent, but a paradigm for screening with the FDT perimeter to improve the overall specificity for glaucoma still must be developed.