Bascom Palmer Eye Institute, University of Miami, Miami, Florida 33136, USA.
Invest Ophthalmol Vis Sci. 2013 Apr 12;54(4):2616-23. doi: 10.1167/iovs.12-11347.
This study investigated the retinal nerve fiber layer (RNFL) reflectance speckle and tested the hypothesis that temporal change of RNFL speckle reveals axonal dynamic activity.
RNFL reflectance speckle of isolated rat retinas was studied with monochromatic illumination. A series of reflectance images was collected every 5 seconds for approximately 15 minutes. Correlation coefficients (CC) of selected areas between a reference and subsequent images were calculated and plotted as a function of the time intervals between images. An exponential function fit to the time course was used to evaluate temporal change of speckle pattern. To relate temporal change of speckle to axonal activity, in vitro living retina perfused at a normal (34°C) and a lower (24°C) temperature, paraformaldehyde-fixed retina, and retina treated with microtubule depolymerization were used.
RNFL reflectance was not uniform; rather nerve fiber bundles had a speckled texture that changed with time. In normally perfused retina, the time constant of the CC change was 0.56 ± 0.26 minutes. In retinas treated with lower temperature and microtubule depolymerization, the time constants increased by two to four times, indicating that the speckle pattern changed more slowly. The speckled texture in fixed retina was stationary.
Fixation stops axonal activity; treatments with either lower temperature or microtubule depolymerization are known to decrease axonal transport. The results obtained in this study suggest that temporal change of RNFL speckle reveals structural change due to axonal activity. Assessment of RNFL reflectance speckle may offer a new means of evaluating axonal function.
本研究探讨了视网膜神经纤维层（RNFL）反射斑纹，并检验了以下假说，即 RNFL 斑纹的时间变化揭示了轴突的动态活动。
使用单色照明研究分离的大鼠视网膜的 RNFL 反射斑纹。在大约 15 分钟内，每隔 5 秒采集一系列反射图像。计算所选区域在参考图像和后续图像之间的相关系数（CC），并将其作为图像之间时间间隔的函数绘制。使用指数函数拟合时间过程来评估斑纹图案的时间变化。为了将斑纹的时间变化与轴突活性相关联，使用在正常（34°C）和较低（24°C）温度下灌流的体外活视网膜、多聚甲醛固定的视网膜和用微管解聚处理的视网膜。
RNFL 反射不均匀；相反，神经纤维束具有随时间变化的斑纹纹理。在正常灌流的视网膜中，CC 变化的时间常数为 0.56±0.26 分钟。在温度较低和微管解聚处理的视网膜中，时间常数增加了两到四倍，表明斑纹图案变化较慢。固定视网膜中的斑纹纹理是静止的。
固定会停止轴突活动；低温或微管解聚处理已知会降低轴突运输。本研究的结果表明，RNFL 斑纹的时间变化揭示了由于轴突活动引起的结构变化。评估 RNFL 反射斑纹可能提供一种评估轴突功能的新方法。
