Eye Formation

Dive Deeper
Baby's eyes form from the interaction of nervous tissue, outer tissue called ectoderm starting 4 weeks after conception. At birth, the newborn is born able to see, but with such low visual acuity that she is legally blind. Visual experience outside the womb helps the visual system finish developing. (Image Credit: Science Source)

The eyes begin forming 22 days after conception.1 Tissue from the developing brain pushes forward towards the face to form an optic cup and the beginnings of the optic nerve, which will connect the eye to the brain. The optic cup becomes the back of the eye, called the retina, which turns light energy into neural signals. The front of the eye, including the cornea and the lens, both form from the surface tissue. Instead of becoming skin, chemical messages from the optic cup turn these structures into transparent tissue. In the sixth week, more surface tissue interacts with the cornea and lens to form the embryo’s eyelids.2 Interestingly, the embryo’s eyelids actually fuse together around 8 weeks after conception, and only reopen about 10 weeks later.3

The front and back of the eyeball fuse together by the eighth week after conception, and muscles start moving the eyes by the tenth week after conception.4 Eye movements can be detected by ultrasound, and can reveal whether a baby is awake, asleep, or dreaming.5

Most infants are born with light blue or gray eyes. A baby’s eye color finalizes between 6 and 12 months old. The color is determined by the distribution of melanin in the iris. Melanin is the same pigment that gives skin its color. If the melanin stays at the back of the iris, then the eye will be blue. If the melanin is found all over the supporting tissue in the iris, then the eye will be brown.6

Major milestones in eye development:

Age Milestone
4th week Lens placode and optic vesicles form.7
5th week Pigments developing in retina.8
6th week Eyelids form.9
8th week The eyeballs finish forming.10 Eyelids fuse together.11
9th week Rods start forming.12
10th week First eye movements detected.13
16th-18th week Layers of the retina are forming.14
18th week Rapid eye movements begin. The eyelids open again.15
23rd week Eyes start functioning.16
26th week First fetal responses to light.17
27th week Fetal pupils respond to light.18