On the movement of lower eyelid

We all know that the upper eyelid is elastic, but we often ignore the movement of the lower eyelid. When I test students, I often ask, "How much does the lower eyelid move when the eyeball looks up and down?" Unfortunately, few people answered.

Due to the action of levator palpebrae superioris, the range of motion of the upper eyelid is much larger than that of the lower eyelid, with the range of15 ~18 mm; The range of lower eyelid movement is 3 ~ 5 mm, in other words, if the lower eyelid does not move, it will block the pupil when we study at our desk. In addition, when you examined the patients with complete congenital ptosis, did you find that the blepharoptosis was bigger when you looked down than when you looked up? This is also because the lower eyelid moves downward, while the upper eyelid does not move. Therefore, it is not reliable to estimate the range of activity of the upper eyelid by the difference of the size of the eyelid fissure when looking up and down.

The movement of the lower eyelid depends on the strength of the lower eyelid retractor. There are not many detailed descriptions of lower eyelid contraction muscles in various ophthalmology and surgery. Among the ophthalmological books I have read, the most clear explanation of the lower eyelid contraction muscle is "Eye Plastic Surgery" written by David T.T T. The lower eyelid contraction muscle is a bundle of fibers separated when the lower rectus muscle passes through the lower oblique muscle, which is wound forward and then merged together, and most of them stop at the lower edge of the lower tarsal plate. A small amount of fibers pass forward through orbital fat to form fat septum; A small number of fibers terminate backward in the conjunctiva of the inferior fornix. The fibers of the lower eyelid contraction muscle do not pass forward through the orbicularis oris muscle but stop under the skin and in front of the tarsal plate, which is different from the fibers of the levator palpebrae superioris muscle. Is there an M between the lower eyelid contraction muscle and conjunctiva? 0? 5. Muscular septum. The function of the lower eyelid contraction muscle is to make the lower eyelid move down and the lower fornix deepen when the eyeball rotates downward. The lower eyelid contraction muscle is a part of the lower rectus muscle, which is called "the extension or extension of the lower rectus muscle" in some books. The lower eyelid contraction muscle should be involved in the plastic surgery of lower eyelid retraction, lower eyelid entropion and lower eyelid ptosis after long-term wearing artificial eyes.