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H Matsuo, G Tomita, Y Suzuki, S Kunimatsu, M Araie; Difference in FDT Outcome in a Normal Hemifield between Early-Stage Open Angle Glaucoma Eyes with Elevated and Normal Intraocular Pressure . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2175.
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Purpose: Frequency-doubling technology (FDT) can reportedly diagnose early glaucomatous changes through detecting damage in magnocellular projecting retinal ganglion cells (M cells), which are more liable to pressure-induced damage. In eyes with open-angle glaucoma(OAG) with visual field defects confined to either lower or upper hemifield, early glaucomatous damage is also likely in the half optic disc corresponding to the spared hemifield. This study aims to study difference in M cell damage between OAG with elevated pressure (primary open angle glaucoma:POAG) and that with normal pressure(normal tension glaucoma:NTG) by FDT outcomes obtained from the spared hemifield. Method: Fifty-eight eyes of 58 early-stage OAG patients with elevated pressure (POAG) patients and 68 eyes of 68 early-stage OAG patients with normal pressure (NTG) with visual field defects as detected by HFA 30-2 program confined to either lower or upper hemifield were included. In FDT testing, patients were first tested with C-20 screening program, then with N-30 threshold program in each regularly visit. Data of the second results obtained with N-30 program were used. FDT-measured thresholds of each test point and its averages (FDT hemifield mean) over the hemifield judged to be normal or abnormal by HFA were compared between the POAG and the NTG groups. Results: Age, refraction (spherical equivalent), and mean deviation (MD) measured by HFA showed no significant of inter-group difference (55.6 ± 10.2 vs 58.6 ± 9.3 years, -3.2 ± 2.8 vs -2.4 ± 3.4 D, and -3.9 ±3.2 vs -4.1 ± 3.3 dB, respectively), while the highest intraocular pressure(IOP) recorded was 24.9 ± 4.4 mmHg in the POAG and 17.6 ± 1.9 mmHg in the NTG group, (p<0.001;Wilcoxon rank sum test). Mean of TD values in either damaged or spared hemifield showed no significant inter-group difference. In the hemifield judged to be normal by HFA, FDT-measured thresholds at 8 of 9 points and FDT hemifield mean (27.5 ± 2.8 vs. 24.4 ± 3.2 dB; p < 0.001) were significantly higher in the NTG than in the POAG group. In the abnormal hemifield, FDT-measured thresholds at all points and FDT hemifield mean showed no significant inter-group difference. Conclusion: The present result suggest difference in contribution of IOP-dependent damage between the two types of OAG and that FDT can sensitively detect IOP dependent damage, being more useful for early detection of glaucoma with elevated IOP.
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