Lander T, Wirtschafter J D, McLoon L K
Department of Ophthalmology, University of Minnesota 55455, USA.
Invest Ophthalmol Vis Sci. 1996 Aug;37(9):1732-9.
The anatomy of individual myofibers within the orbicularis oculi muscle was examined to determine individual myofiber lengths in the different regions of the muscle. A wide variety of eyelid conditions require eyelid surgery or drug injections directly into the eyelid. Knowledge of regional myofiber anatomy and physiology is important for accurate treatment of these conditions.
Eyelid specimens from rabbits were treated with collagenase, fixed, and stained for neuromuscular junction location. Individual myofibers were dissected from these muscle specimens and were measured to determine individual myofiber length and neuromuscular junction position. Additional eyelid specimens of rabbits and humans were stained en bloc to visualize neuromuscular junction location in the pretarsal and preseptal regions of the orbicularis oculi muscle.
The myofibers showed variable lengths, shorter in the pretarsal region of the muscle and longer in the preseptal region. The average individual myofiber length in the pretarsal region was 36% as long as the entire length of the pretarsal muscle region. In the preseptal region, the myofibers were slightly longer, covering 54% of the entire length of this region of the muscle. In both the pretarsal and preseptal regions of the rabbit and human orbicularis oculi muscle, there were many clusters of neuromuscular junctions throughout the medial to lateral length of the muscle, with the majority of the neuromuscular junctions in the medial and lateral canthal regions of the preseptal portion of the lid. This indicates that the muscle is composed of relatively short, overlapping myofibers, and that the shortest myofibers reside in the medial and lateral canthal regions of the eyelid. Multiple innervation of one rabbit myofiber was observed as a rare occurrence.
Individual myofibers of the orbicularis oculi muscle are relatively short, end intrafascicularly, and are of heterogeneous lengths varying regionally within the muscle. Thus, for drug injections into the eyelid, optimal drug effectiveness may require treatment of the entire lid from medial to lateral canthus to overcome the tissue barriers to diffusion. The existence of muscle fibers of heterogeneous lengths suggests that the complex organization of muscle fibers may play previously unappreciated but important roles in normal function, pathophysiology, and age-related changes in the eyelid.
研究眼轮匝肌内单个肌纤维的解剖结构，以确定该肌肉不同区域的单个肌纤维长度。多种眼睑疾病需要进行眼睑手术或直接向眼睑注射药物。了解区域肌纤维的解剖结构和生理功能对于准确治疗这些疾病很重要。
对兔眼睑标本用胶原酶处理、固定，并对神经肌肉接头位置进行染色。从这些肌肉标本中分离出单个肌纤维，并进行测量以确定单个肌纤维长度和神经肌肉接头位置。对兔和人类的额外眼睑标本进行整体染色，以观察眼轮匝肌睑板前和眶隔前区域的神经肌肉接头位置。
肌纤维长度各不相同，在肌肉的睑板前区域较短，在眶隔前区域较长。睑板前区域单个肌纤维的平均长度为睑板前肌肉区域全长的36%。在眶隔前区域，肌纤维稍长，覆盖该区域肌肉全长的54%。在兔和人类眼轮匝肌的睑板前和眶隔前区域，在肌肉内侧至外侧的长度范围内有许多神经肌肉接头簇，大多数神经肌肉接头位于睑眶隔前部的内外眦区域。这表明该肌肉由相对较短、相互重叠的肌纤维组成，最短的肌纤维位于眼睑的内外眦区域。观察到一条兔肌纤维有多个神经支配，这种情况较为罕见。
眼轮匝肌的单个肌纤维相对较短，在肌束内终止，且长度各异，在肌肉内不同区域有所不同。因此，对于向眼睑注射药物，为达到最佳药物效果，可能需要从内眦到外眦对整个眼睑进行治疗，以克服组织扩散障碍。不同长度肌纤维的存在表明，肌纤维的复杂组织结构可能在眼睑的正常功能、病理生理以及与年龄相关的变化中发挥着此前未被认识但很重要的作用。
