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Eye development is initiated by the master control gene PAX6, a homeobox gene with known homologues in humans (aniridia), mice (small eye), and Drosophila (eyeless). The PAX6 gene locus is a transcription factor for the various genes and growth factors involved in eye formation. [1] [5] Eye morphogenesis begins with the evagination, or ...
During embryonic development of the eye, the outer wall of the bulb of the optic vesicles becomes thickened and invaginated, and the bulb is thus converted into a cup, the optic cup (or ophthalmic cup), consisting of two strata of cells.
Human embryonic development covers the first eight weeks of development, which have 23 stages, called Carnegie stages. At the beginning of the ninth week, the embryo is termed a fetus (spelled "foetus" in British English). In comparison to the embryo, the fetus has more recognizable external features and a more complete set of developing organs.
The convergence of each eye on a particular object and the stereopsis, also known as the retinal disparity among two objects, provides some information for infants older than ten weeks. With binocular vision development, infants between four and five months also develop a sense of size and shape constancy objects, regardless of the objects ...
The puzzle of how embryonic development was controlled began to be solved using the fruit fly Drosophila melanogaster as a model organism. The step-by-step control of its embryogenesis was visualized by attaching fluorescent dyes of different colours to specific types of protein made by genes expressed in the embryo. [9]
The eyes begin to develop as a pair of diverticula (pouches) from the lateral aspects of the forebrain.These diverticula make their appearance before the closure of the anterior end of the neural tube; [1] [2] after the closure of the tube around the 4th week of development, they are known as the optic vesicles.
After about age 20 the lens grows rounder again and the iris is very important for this development. [4] Several proteins control the embryonic development of the lens though PAX6 is considered the master regulator gene of this organ. [19] Other effectors of proper lens development include the Wnt signaling components BCL9 and Pygo2. [20]
[18] [19] [20] Such high-level genes are, by implication, much older than many of the structures that they control today; they must originally have served a different purpose, before they were co-opted for eye development. [15] Eyes and other sensory organs probably evolved before the brain: There is no need for an information-processing organ ...