Frequency doubling perimetryによる緑内障性視野異常の長期変動

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【目的】Frequency doubling technology (FDT)は従来の自動視野計とは異なり, 比較的大きな網膜神経節細胞であるM細胞系の機能を評価している。本来緑内障スクリーナーとして開発されており短時間での検査が可能である。緑内障において, この視野計がスクリーニング以上に臨床的な経過観察に有用であるか, 視野の長期変動(1ong-term fluctuation=LF)について従来の視野計と比較検討した。【方法】開放隅角緑内障患者35例35眼に対し, HFA (Humphrey field analyzer)30-2とFDT threshold c-20を4ヶ月ごとに1年間に3回測定し, 視野全体の感度低下を示す視野指数MD (mean deviation), 局所的異常を示す視野指数PSD (pattern standard deviation), CPSD (corrected pattern standard deviation)について3回の測定結果より長期変動を求め, その結果を比較した。【結果】1年間を通して眼圧には有意な変化を認めなかった。FDTにおけるMDの長期変動は0.94dBでHFAのMDの長期変動1.06dBと有意差は無かった。FDTの各測定点の長期変動は中心では1.8dBであるのに対し, 周辺では2dBから3dBと大きかった。HFAのMDとCPSDは1年間で有意な変化は認めなかった。FDTのMDとPSDは3回目の測定で有意に悪化した。各測定時期の視野指数MDとPSDはFDTとHFAで有意の相関を認めた。【結論】FDTの視野指数MDとPSDはHFAの視野指数MDとPSDと同様の変動を示し, 各時期において有意の相関を示すことがわかった。このことより緑内障性視野異常の経過観察にFDTを用いることが可能であることがわかった。

Purpose: We studied the long-term fluctuation of glaucomatous visual field defects measured by frequency doubling perimetry to compare that by Humphrey field analyzer (HFA) over time. Methods: The subjects included 35 consecutive patients with primary open angle glaucoma. Visual fields were examined with HFA central 30-2 and frequency doubling technology (FDT) threshold c-20 every 4 months within one year. Mean deviation (MD) and corrected pattern standard deviation (CPSD) measured with HFA were compared among 3 results. MD and PSD with FDT were compared among 3 results. Long-term fluctuation was determined as standard deviation of MD and sensitivity at each point with the 3 results of FDT. Long-term fluctuation of MD was compared between FDT and HFA. Visual field indices were compared between FDT and HFA at every interval. Results: Long-term fluctuation of MD with FDT was almost the same as that with HFA. Long-term fluctuation of sensitivity at each point with FDT did not vary with eccentricity except at the center. Intraocular pressure and MD and CPSD with HFA did not change within one year, but MD and PSD with FDT deteriorated at the third test results. A significant correlation was found in terms of visual field indices between FDT and HFA at every interval. Conclusion: The visual field indices with FDT fluctuated in a similar way to those with HFA and correlated with those with HFA over time.