FIG. 1.

The process of eyelid fusion. A, At around week 8, the flattened periderm cells (arrowhead) undergo a morphogenetic and proliferative change into rounded or cuboidal periderm cells. B, The leading edge of these proliferating cells helps make contact with the advancing edge of the opposing eyelid periderm cells until a connection is established. C, When a connection is established between both sides, these periderm cells flatten again and form a continuous sheet ultimately covering the cornea. D, Only the periderm and epidermal layers are involved in eyelid fusion while eyelid mesenchyme (*) remains distinct (Modified with permission from Yu et al.³²).