Corneal development associated with eyelid opening.

The development of the cornea as a tissue initiates as early as five weeks in the human embryo. This development continues gradually until the time of eyelid opening, which is associated with major developmental changes. These events, most easily observed in rodents, which are born with closed eyelids, include alterations in the rate of cell proliferation in the epithelium, stroma and endothelium; differentiation of the epithelium; appearance of a tear film and tear-film-associated proteins; and swelling and thinning of the stroma. Eyelid opening is also associated with numerous alterations in gene expression. These events are the subject of this review. Readers are directed to the article by Wolosin et al., also in this volume, for an in-depth discussion of early corneal development.