Eye Field - Vertebrate Eye
The development of eyes starts with evagination of the lateral wall of the forebrain. one on each side, which make the optic vesicles. By vital dye staining it is established that at the open neural plate state in amphibians the presumptive material for the optic vesicle take place in the median anterior region of the neural plate. This region is termed as the eye field. After that this field gets divided into two lateral portions, one for each eye. The lens fields lie outside the neural plate in the epidermal ectoderm. In the chick the eye field has been recognized as a broad median area in the anterior part of epiblast in front of the Hensen's node at primitive streak stage. By 8-sonite stage middle part of the eye field in chick embryos has lost the capacity to make the eye, but the two lateral parts retain this capacity and each forms a complete eye. Treatment of eggs with a number of chemicals like lithium chloride choretone etc. or removal of the chorda-mesoderm from below the anterior region of neural plate avoids the division of the median eye field and a single median eye (cyclopean eye) is made instead of two lateral eyes.
The term field or more precisely the morphogenetic field of an organ may be described as the sum total of properties of the cells of that region of the embryo from which the specific organ or structure will develop. Normally, the structure concerned forms from cells in the central part of the field. However the properties to form that organ generally extend to some distance peripherally beyond the limits of the region which contributes cell for construction of the organ normally. Hence in the nonexistence of the central part of the field cells around it may make the structure.