Pulley Morphological Research Of Extraocular Muscles By Anatomical And Imagology Method

Objective:to study Pulley's structure of extraocular muscles and applications of pulley's theory in clinical diagnosis and treatment of ocular disease.Methods:Pulley's structure observation: orbits were cracked by bone shears, periosteum and fat were removed, extraocular muscles were carefully dissected and followed each muscle belly to reached the surface of Tenon's capsule.The connective tissue around the Pulley's structure was carefully removed. Then the length of Pulley's structure from the point of membrane attachment to Pulley was measured and recorded. Pulley tissues were fixed in 4% paraformaldehyde for 2 hours. Paraffin section for HE staining, Masson trichrome stain and F-actin staining to confirm the structure was performed. Imaging observation:six healthy volunteers,age 24 to 37 years,29.5 years on average,without nystagmus and ocular dyskinesia were selected for this experiment. On five points of fixation including original and the second spacing, subjects were scanned by MRI on horizontal position,sagittal position and frontal position.The data about Pulley structure were obtained and analyzed on MRI.Result: Pulley structures were observed from anatomical specimen,which were located at the points where rectus muscles penetrate Tenon's capsules.The connective tissue fascia of Tenon's capsules anti-thickening pack, were very closely attached to the surface of the eye muscles,not easily stripped from extraocular muscles. The connective tissue of Pulley structure between medial rectus and inferior rectus ,lateral rectus and superior rectus was thicker than the one between superior rectus and medial rectus ,inferior rectus and lateral rectus. Pulley structure was mainly composed of large mumber of collagen fibers and some smooth muscles, which was proved by H-E staining ,Masson trichrome staining and F-actin staining experiment. Observation through MRI dynamic state scanning: when eyes were at orthophoria front position, internal and external rectus muscle and eyes position was at equal pace. When eyes heterotropy to left,there appear a angle between the left internal rectus muscle and the right external rectus muscle,named urgent turn off phenomenon.The same phenomenent show up when eyes heterotropy to right.Conclusion:1.There is a compact connective tissure which packs the eyeball near end of the extraocular muscle, and the interconnection forms a complete connective tissure sheath .The rear margin of the sheath is consistent with the retrobulbar polar plane. This is called Pulley structure .2.The MRI dynamic scanning indicated that the extraocular muscle has the function the Pulley structure showed indeed, and the acute turning point is consistent with the rear margin of the sheath which is observed in this article, while the fiber controlled ligament connected with orbital wall is existed between sclera anterior border plane and the aequator plane. Therefore the originally incorrect recognition that the Pulley structure is point functional or the fiber trochlea functional, new discovery proved that the Pulley function is the result by complete fiber connective tissure sheath of the extraocular muscle function as a whole .