Parents often notice that a premature baby’s eyes look different from a full-term infant’s, reflecting incomplete development. Premature birth, defined as delivery before 37 weeks of gestation, interrupts the final, rapid stages of fetal development. The eyes are particularly susceptible because their most delicate structures finish maturing late in the third trimester. These differences are a common consequence of being born early and require specialized medical attention to ensure healthy visual development.
The Timeline of Fetal Eye Development
The eye begins to form early in pregnancy, but structures needed for sight are the last to fully mature. Major parts, including the cornea, lens, and retina, start developing around the seventh week of gestation. Retinal blood vessels do not begin to grow until about 16 weeks of pregnancy.
These retinal vessels grow outward from the center to the periphery, a process completed only around 40 weeks. When an infant is born prematurely, this vascular system is unfinished, leaving a section of the retina without a normal blood supply. Additionally, the eyelids, often fused shut until about 27 weeks, may appear thin and immature, and pupils may not fully constrict in response to light until 30 to 32 weeks.
Visible Differences and Coordination Issues
Incomplete development leads to several observable differences in premature infants. For babies born very early, the eyelids may appear thin, and in extremely premature cases, they may still be fused shut. The eyes may lack the fat padding typical of a full-term baby, resulting from the absence of third-trimester weight gain.
The eyes may also exhibit coordination problems because the neurological pathways controlling movement are still maturing. Transient strabismus, or crossed eyes, is common as the muscles learn to work together, and this is more prevalent in premature infants than in term babies. Some babies experience nystagmus, which is involuntary, rapid, and repetitive eye movements, reflecting the immaturity of the central nervous system’s control. While many coordination issues resolve as the nervous system matures, they require close monitoring.
Understanding Retinopathy of Prematurity
Retinopathy of Prematurity (ROP) is the most serious concern related to incomplete retinal vessel development. This vasoproliferative disorder occurs when the normal growth of retinal blood vessels halts prematurely. After birth, the retina’s unbalanced need for oxygen and nutrients triggers the abnormal proliferation of new, fragile vessels that grow haphazardly.
Risk for ROP is highest in infants born before 32 weeks gestation or with birth weights less than 1,500 grams. The disease progresses through five stages. Stages 1 and 2 represent mild to moderate vessel abnormality that often resolves without intervention.
Stage 3 involves the growth of abnormal vessels into the vitreous gel, which can lead to scarring. In the most advanced stages, the abnormal vessels and scar tissue contract, pulling the retina away from the back of the eye. This retinal detachment (Stages 4 and 5) can cause severe vision loss or blindness if not promptly treated. The oxygen-rich environment of the NICU, while life-saving, can influence ROP progression by disrupting the balance of growth factors.
Long-Term Visual Outcomes and Necessary Care
Although ROP often regresses without lasting vision problems, premature birth increases the risk for long-term visual issues, even after the retina matures. Premature infants are more likely to develop refractive errors, especially myopia (nearsightedness), which requires corrective lenses. They are also at higher risk for amblyopia (lazy eye), where one eye develops poorer vision because the brain favors the other.
The increased likelihood of strabismus (eye misalignment) persists into childhood, often requiring ongoing management. Since the most serious initial problems with ROP are not visible, a mandatory screening protocol is implemented while the baby is in the NICU. These screenings involve specialized examinations by a pediatric ophthalmologist to monitor retinal blood vessel growth.
After discharge, long-term follow-up care is important, especially for those born before 32 weeks gestation. Regular pediatric ophthalmology appointments are needed to detect and manage delayed-onset conditions like strabismus, amblyopia, and refractive errors that can manifest years later. Compliance with this care ensures potential visual challenges are addressed early, maximizing the child’s visual potential.