The development of the lens placode is typically seen between 44 and 50 hours; invagination occurs shortly after at around the 50–55-hour mark.

[2] Chick embryos studies show the lens placode contains a cuboidal to columnar cell shape and that it is not multilayered.

[2] The restricted expansion hypothesis” states that the adhesion of the ectoderm cells to the matrix is a key factor in the lens placode formation.

[3] SOX2 is a transcription factor that works alongside Pax6 to develop the lens placode.

[4] This article incorporates text in the public domain from the 20th edition of Gray's Anatomy (1918)