Anatomic And Histological Research Of Levator Muscle-Müller’s Muscle Complex And Its Clinical Application

Objective:(1)The gross anatomy of the upper eyelid was studied to observe the anatomical structure characteristics and adjacent relationships of different structures of the upper eyelid,especially focusing on the levator muscle-Müller’s muscle complex.The study included the anatomical characteristics,origin,insertion and adjacent anatomical structure of it,providing anatomical theories for upper eyelid blepharoplasty.(2)The histological study of upper eyelid was conducted to observe and analyse the different structures of upper eyelid,paying mainly attention to the histological structures of levator palpebrae superioris,levator aponeurosis,and Müller’s muscle.(3)According to the results of upper eyelid of gross anatomy and histology,the posterior layer of levator aponeurosis advancement was used in double eyelid surgery.Materials and Methods:(1)Gross anatomy of 5 right upper eyelids of 5 Chinese cadaveric specimens(four male;age range 77-86 years,mean age 81.5±3.6 years;one female,79 years)was fixed by formalin was studied.All of the specimens were harvested from the Department of Anatomy and Histology,Nanjing Medical University.None of the cadavers had any history or clinical evidence of a previous eyelid or orbital trauma,Graves’ orbitopathy,strabismus,or any other periocular pathologic feature.From outside to inside,the upper eyelid was dissected layer by layer to expose the following structures which included skin,subcutaneous tissue,orbicularis oculi muscle,retro-orbicularis oculi fat,orbital septum,orbital fat,levator aponeurosis and levator palpebrae,Whitnall’s ligament,post-levator aponeurosis fat pad,Müller’s muscle and conjointfascial sheath.(2)Histological studies were conducted on 13 upper eyelid tissue specimens from 10 Chinese cadavers,including 8 males with an average age of 76.9±8.0years(6male cadavers were obtained the left upper eyelid,and 2 male cadavers were obtained the left upper eyelid),a 82 years old female(both left and right upper eyelid),and one10-year-old child specimen obtained the left upper eyelid.All specimens were performed routinely with 10% formalin.They were embedded routinely in paraffin,sectioned sagittally,and stained with hematoxylin-eosin(HE)staining for general examination,and Masson trichrome staining for examination of collagenous fibers,and anti-smooth muscle actin antibodies for smooth muscle(α-SMA).The histological study was performed to observe the following structures which included skin,subcutaneous tissue,orbicularis oculi muscle,retro-orbicularis oculi fat,orbital septum,orbital fat,levator aponeurosis,post-levator aponeurosis fat pad and Müller’s muscle.(3)Retrospective study was performed on 20 patients with mild blepharoptosis(March 2018 to March 2020)who underwent the technique for correction of mild ptosis combined with upper eyelid blepharoplasty.Levator aponeurosis posterior layer advancement technique was used to correct mild ptosis in double eyelid surgery.The follow-up time was 3 months.And the following indexes were measured and evaluated,which included visual acuity,the height and symmetry of double eyelid line,undercorrection,overcorrection,satisfaction of patients.Result:(1)From outside to inside,the hierarchical structure of upper eyelid was observed,which included the skin,subcutaneous tissue,orbicularis oculi muscle,retro-orbicularis oculi fat(ROOF),orbital septum,orbital fat,levator aponeurosis and levator palpebrae surperioris,post-levator aponeurosis fat pad,Müller’s muscle,tarsal plate and palpebral conjunctiva.The volume of ROOF and orbital fat was significantly different in different age individuals,while the volume was less in the older samples.The levator palpebrae superioris gave off branches below the Whitnall’s ligament,which included anterior and posterior layers.The anterior branch of levator palpebrae superioris became levator aponeurosis,and the posterior branch of levator palpebrae superioris was associated with Müller’s muscle with a fat pad between them and also had extensions into orbicularis and subcutaneous tissue.There was almost no obvious fat structure in the subcutaneous tissue in front of the tarsus,and the orbicularis oculi muscle was adhered closely to the pretarsal fascia.This fascia tissue of the anterior tarsus had no obvious dividing area,and part of it was loosely connected to the tarsus,which could be lifted with forceps.There was a adipose tissue structure between the levator aponeurosis and Müller’s muscle,which was called the post-levator aponeurosis fat pad.(2)The tissue structure of the whole upper eyelid could be clearly observed in the HE staining,but Masson staining showed skin,muscle,aponeurosis,fat,blood vessels,tarsus and other structures more clearly.The anterior layer of aponeurosis levator was fused with orbital septum.The posterior layer of the levator aponeurosis had different extension paths that diverge at the level of the attachment site of the orbital septum onto the levator aponeurosis.It lies almost parallel to the extension line of the levator aponeurosis,at the confluence of these two structures.Below the confluence,most of these fibers inserted into the orbicularis oculi muscle,whereas the others reached to the margin of the tarsal plate.In every specimens,the posterior layer of levator aponeurosis could be positive stained by anti-smooth muscle actin antibodies.The post-levator aponeurosis fat pad,locating between the levator palpebrae superiors and Müller’s muscle,was a adipose tissue structure and extended upward to the levator palpebrae superiors.In the specimens of levator muscle with branches,the fat pad was distributed at the branches of levator palpebrae superioris,and in the specimens without branches,the fat pad was distributed at the junction area between levator aponeurosis and levator palpebrae superioris.(3)Twenty patients treated with double eyelid surgery combined with posterior layer of levator aponeurosis advancement.The morpholoy of double eyelid was symmetrical after operation,and mild ptosis was corrected.The 18/20(90%)patient was satisfaction with the outcomes.Two patient was dissatisfaction and underwent the revision.No eyelash drooping,exposure keratitis,eyelid incompleteness,eyelid ectropion and other complicationsConclusion:Gross anatomy can better reveal the characteristics of the upper eyelid tissue structure,while histology can observe and analyze the upper eyelid tissue structure that is difficult to accurately identify in gross anatomy.Based on the double-layer structure and the characteristics of the levator aponeurosis,the levator aponeurosis posterior layer advancement in double eyelid blepharoplasty can correct mild ptosis without opening the orbital septum.