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C. V. Albanis, R. A. Quinones; Use of Matrix Frequency Doubling Technology (FDT) to Assess Visual Field Status Following Unreliable Standard Automated Perimetry (SAP). Invest. Ophthalmol. Vis. Sci. 2008;49(13):1078.
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Reliable visual field (VF) testing is paramount to the diagnosis of glaucoma and determination of progression of disease. SAP is the standard for monitoring progression of VF defects in glaucoma. Some patients, however, do not test reliably with SAP. First generation FDT VF were used as a screening tool for glaucoma. Compared to prior versions, the HumphreyTM Matrix FDT uses more stimuli, distributed in a pattern similar to the 24-2 used in SAP. Some suggest that this new program, with more targets, located at narrower intervals, may detect VF defects and monitor progression more accurately. We hypothesize, while not ideal for monitoring all glaucoma patients, Matrix FDT may be used as an alternative for patients who have unreliable VF with SAP. This study compares the reliability of Matrix FDT in glaucoma suspects and in patients with primary open angle glaucoma (POAG), who had unreliable testing using SAP.
This is a retrospective chart review of 20 eyes (10 patients) from August to November 2007, who were followed as glaucoma suspects, or were diagnosed with POAG. SAP was performed with the HumphreyTM Field Analyzer II using the 24-2 SITA standard test. FDT testing was performed using the HumphreyTM Matrix 24-2 with Welch Allyn® FDT.
We reviewed 20 eyes who had unreliable SAP testing, with subsequent FDT. The average age was 69.5 years old. Fifty percent had POAG, while the others were glaucoma suspects. Visual acuity was 20/20 (in 8/20 eyes) to 20/50 (in 1/20 eyes). Mean IOP was 18.75 (range 13 - 23). The patients each had an average of 5.1 (range 2- 11) unreliable SAP VF prior to undergoing the FDT. Comparing reliability measures: of the 20 eyes, average fixation losses (FL) for SAP was 47% (range 0 - 87%), compared to 7.5% for FDT (range 0 - 40%). Seventeen of 20 eyes (85%), had 0 - 10% FL with FDT. False positives ranged from 0 - 43% (mean 11.8%) for SAP, compared to 0 - 10% (mean 3%) for FDT. Review of false negative (FN) errors using SAP was 8.9% (range 0 - 33%), compared to 0% for FDT (all twenty eyes had zero FN readings).
An unreliable SAP VF makes it difficult to diagnose glaucoma or assess progression of the disease. We believe that with lower fixation losses, false positives and false negative readings, FDT may be used in patients with repeatedly unreliable SAP testing. Further research needs to be done to assess the value of FDT in such patients, and compare the reproducibility and level of accuracy of FDT compared to SAP in these patients.
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