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CA Girkin, J De Leon-Ortega; Extent of Visual Dysfunction Measured by Frequency Doubling Technology (FDT) Perimetry in Altitudinal Visual Field Loss Secondary to Non-Arteritic Ischemic Optic Neuropathy (NAION) . Invest. Ophthalmol. Vis. Sci. 2002;43(13):912.
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Purpose:FDT has not been extensively evaluated in non-glaucomatous optic neuropathies such as NAION. FDT may demonstrate more extensive damage in NAION as in glaucomatous optic neuropathy, or conversely, the frequent altitudinal defects in NAION may limit its usefulness due to increased ocular scatter across the horizontal raphe as has been demonstrated with hemianopias across the vertical midline. This study will determine if visual functional abnormalities in altitudinal NAION are more extensive with FDT than with SITA standard perimetry. Methods:20 eyes of 14 patients diagnosed with NAION with altitudinal defects on SITA were examined using FDT. The percentage of abnormal test locations (points outside the 95% confidence interval on total deviation plot) for the involved and uninvolved hemifield were calculated for each technique. To ensure differences in scotoma area between FDT and SITA were not a consequence of patients with small disc area, 20 eyes of 10 normal subjects matched for disc area and age were also tested. Results:Global parameters between FDT and SITA were highly correlated (MD, rho= 0.78, p<0.001, PSD, rho=0.77, p<0.001) Average defect size (% of abnormal test locations) was similar in the hemifield containing the altitudinal defect (SITA=93.3%, FDT=93.9%), but in the contra-lateral hemifield, FDT revealed more extensive loss than seen with SITA (SITA=9.2%, FDT=42.2%) Controls demonstrated minimal abnormalities on either task (SITA=0.02%, FDT=0.02%). The altitudinal nature of field loss was evident in 18 of 20 eyes. Conclusion:FDT demonstrates more extensive defects in some patients with NAION with abnormalities extending into the hemifield that was relatively intact using SITA, indicating that damage in altitudinal NAION may be more diffuse than has been estimated by conventional techniques.
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