The Anatomical Study Of The Extraocular Check Ligament System And Its Mechanics In Correction Of Blepharoptosis

BackgroundCongenital blepharoptosis is a rare condition characterized by an abnormal drooping of the upper eyelid.Not only has a negative impact on patients' appearance,it also limits their vision.In recent years,the procedure of suspension of the eyelid to the conjoint facial sheath(CFS)became more and more popular as a relative new method at home.Many Chinese researchers reported their operation studies and recommended this method,some even suggested that it could replace traditional techniques to correct Blepharoptosis.Although there are many anatomical studies on the check ligament of the superior fornix,there is still controversy in understanding the composition,morphology,area and physiological functions,which may impact the application of this technique.We hope to further clarify structural features and physiological functions to promote clinical application by anatomical study and mechanics study with surgery simulation.Method1.Anatomical StudyFour fixed and three fresh cadavers of Chinese adults were used.Gross dissection was performed on fourteen eyes.We identified the anatomical relationships between CFS,the superior rectus and the levator palpebrae superioris first.We also identified the relationships between the extraocular ligament system which CFS belongs to,the medial and lateral canthus,the rectus,the obliquus and the orbital wall by further dissection.2.Histology StudyThe three specimens six eyeballs were treated with dehydration,fixation and paraffin embedding,and then,sagittal,horizontal and coronal sections were made.The sections were stained with HE and Masson in order to observation the relationships of the surrounded structures with the extraocular check ligament system.Some regions of the sections were stained by immunohistochemistry,using antibodies,such as ?-SMA and h-caldesmon so that identify the composition of the check ligaments.3.Mechanics Study of the procedure of suspension of the eyelid to the CFSTwo fresh specimens of Chinese adults were cut off from supraorbital margin to infraorbital margin.Opened the orbital roof and then perform the operation of suspension of the eyelid to the CFS.Pulling the superior rectus and the levator in same distances before and after the simulation operation.Measured the altitude that the eyelids had been lift in each case and then infer the mechanism that how does this procedure corrects the blepharoptosis.Result1.Anatomical StudyIn our gross dissection,below the levator upon the superior rectus,the check ligament(CFS)that Lockwood has described is found.It isn't only restricted upon the eyeball.The ligament extends bilaterally and attaches to the orbital wall behind the inner and lateral canthus tendon.Between the inferior obliquus and the inferior rectus we also find sheath structure similar to the check ligament extends bilaterally to the orbital wall.These two structures form an annular fascial system surround the eyeball.2.Histology StudySagittal,horizontal and coronal sections were made.We observe the anatomical relationships of the check ligaments of each eye muscle with the muscles,fat,fornix and canthus from the three derection.Then we confirm the existence of annular fascial system and its close connection with the orbital wall.The medial half of the fascia sheath is tenacious and the immunohistochemical test proves that smooth muscle cells are found in this part.3.Mechanics StudyThe applicable parts of each specimens were cut off.The we simulated the eyelids movement under three circumstances: normal physiological state,blepharoptosis and after being taken the operation of suspension of the eyelid to the CFS.We pulled the superior rectus and the levator in same distances in each case and then found out that the main power which lift the eyelid after the procedure was from the dynamic contraction of the levator,meanwhile the static suspension force of the superior rectus also affect the position of the eyelids.The effect which superior rectus made to raise the eyelids was enhanced postoperatively.ConclusionWe call this whole annular fascial sheath structure surround the circumocular muscle “Extraocular Check Ligament System”(ECLS).According to its form and histologic components the ECLS may plays a restrict and check role in the movement of the eyeball and the eyelids.The simulation of the muscles and the eyelids before and after the operation further explained the mechanism of the operation of suspension of the eyelid to the CFS.The theory we summarized may provide anatomical basis and reference for clinical application and modification of this controversial operation.