An Anatomic Investigation of Human Fetal Upper Eyelid

In this study, the authors investigated the anatomic morphology of the upper eyelid in prenatal human fetuses to elucidate the cause of congenital palpebral conditions such as congenital blepharoptosis. Although much has been published on the anatomy of the adult upper eyelid, hardly any reports have dealt with neonatal morphology in the immediate postpartum period or infants and children. From a developmental perspective, to better understand the development and aging effects in the upper eyelid, knowledge is needed of the anatomic characteristics of the upper eyelid in neonates immediately after birth. Also, to elucidate the cause of congenital blepharoptosis, the authors investigated the anatomy of the upper eyelid in human fetuses. Subjects comprised 6 Japanese fetuses between 6 and 10 months of gestation for a total of 12 eyelids. Sagittal tissue slices of the excised upper eyelid were embedded in paraffin, sliced thinly, then stained with HE and Van Gieson. The specimens were carefully examined under light microscopy. Next, these samples were compared with adult upper eyelid tissue images to determine differences in development and morphology. Fetal characteristics observed were as follows: the morphologic characteristics of the palpebrae superioris muscle and levator aponeurosis were underdeveloped and connections to the orbicularis oculi muscle were sparse, whereas the Müller muscle was markedly thicker than those in adults. Fetal eyes tend to be closed in amniotic fluid, and so before fetuses begin to move, the levator palpebrae superioris muscle tends to be poorly developed, whereas eye-opening is speculated to be controlled primarily by Müller muscle. Findings suggest muscle fibers develop due to eye-opening movements, and the differentiation and development of the levator palpebrae superioris muscle are believed to be closely related to the development of congenital blepharoptosis.