Mühlendyck H
Z Gerontol. 1979 Jan-Feb;12(1):46-59.
Muscle fibers of extraocular muscles (M. rectus internus, M. rectus externus and M. rectus inferior) from 27 patients ranging in age from birth to 83 years were measured planimetrically in cross sections between the origin-, insertion-, and middle-thirds of the muscle length. In all the muscles the middle third of the muscle possessed fibers with an average thickness greater than in the third of the muscle at either end (origin or insertion). This observation was, however, dependent on the age of the patients. This difference in muscle fiber thickness was most constant in patients in the age groups 20 to 30 and 40 to 50 years. On patients 60 years and older, the muscle fibers in all portions of the muscle were thicker; however, the M. rectus externus and especially the M. rectus internus also possessed a larger number of thinner fibers. The percent of thin fibers in the M. rectus internus was even greater than that found in one year-old patients. These observations are most likely explained by a decrease in the accomodation capacity in older patients and a correlative reduced convergence activity of the muscle fibers that are only active during convergence, resulting in decreased demand on the muscle fibers and their consequent atrophy.
对27例年龄从出生到83岁患者的眼外肌（内直肌、外直肌和下直肌）的肌纤维，在肌长度的起始部、附着部和中部三分之一之间的横切面上进行了面积测量。在所有肌肉中，肌中部三分之一的纤维平均厚度大于两端（起始部或附着部）三分之一的纤维。然而，这一观察结果取决于患者的年龄。肌纤维厚度的这种差异在20至30岁和40至50岁年龄组的患者中最为恒定。在60岁及以上的患者中，肌肉各部分的肌纤维都更厚；然而，外直肌，尤其是内直肌也有大量较细的纤维。内直肌中细纤维的百分比甚至高于1岁患者。这些观察结果很可能是由于老年患者调节能力下降以及仅在集合时活跃的肌纤维的集合活动相应减少，导致对肌纤维的需求减少以及随之而来的萎缩。
