EARLY EYE DEVELOPMENT
The human eye begins to develop during the 17th day of gestation. Mesoderm cells, the middle layer of the blastoderm, and ectoderm cells, the outer layer of the blastoderm, form the eye fields in the neural area of the embryo. Optic vesicles develop in the eye fields and in five days, infold to form the optic cup. At this point, the retina and crystalline lens begin to develop. Meanwhile, surface ectoderm cells are becoming thicker. The lens forms from these thickened cells. By the 32nd day, you can easily identify the lens, and during the next three to three and a half weeks the lens will grow to the size it will be at birth.
1. Cross-section of embryonic mouse eye (seven weeks comparable to human development). Orange area is the developing cornea, blue is the lens cavity and green is the posterior lens fibers.2. Cross-section of embryonic human eye at eight weeks gestation. Pink area is the corneal epithelium, and blue is the inner layers.3. Eyelid formation in human embryo at eight weeks gestation.