Premature Infant Retinal Disorder

Retinopathy of Prematurity (ROP), also called retrolental fribroplasia, is abnormal blood vessel development that may occur in some premature babies. The retina is located at the back of the eye. The retina transmits nerve messages about what is seen to the brain for processing. When some babies are born prematurely, the blood vessels that supply the retina are not developed completely, leaving the retina without a blood supply. Severe ROP may lead to vision problems or blindness. Infants with mild ROP may make full recoveries. ROP may be treated with surgery.

The eyes and brain work together with amazing efficiency. Light rays enter the front of the eye and are interpreted by the brain as images. Light rays first enter your child’s eye through the cornea, the “window” of the eye. The cornea is a clear dome that helps the eyes focus.

The anterior chamber is located behind the cornea and in front of the iris. The anterior chamber is filled with a fluid that maintains eye pressure, nourishes the eye, and keeps it healthy. The iris is the colored part of your child’s eye. Eye color varies from person to person and includes shades of blue, green, brown, and hazel. The iris contains two sets of muscles. The muscles work to make the pupil of the eye larger or smaller. The pupil is the black circle in the center of the iris. It changes size to allow more or less light to enter your child’s eye.

After light comes through the pupil, it enters the lens. The lens is a clear curved disc. Muscles adjust the curve in the lens to focus clear images on the retina. The retina is located at the back of your child’s eye.

The inner eye, the space between the posterior chamber behind the lens and the retina, is called the vitreous body. It is filled with a clear gel substance that gives the eye its shape. Light rays pass through the gel on their way from the lens to the retina.

The retina is a thin tissue layer that contains millions of nerve cells. The nerve cells are sensitive to light. Cones and rods are specialized receptor cells. Cones are specialized for color vision and detailed vision, such as for reading or identifying distant objects. Cones work best with bright light. The greatest concentration of cones is found in the macula and fovea at the center of the retina. The macula is the center of visual attention. The fovea is the site of visual acuity or best visual sharpness. Rods are located throughout the rest of the retina.

The eyes contain more rods than cones. Rods work best in low light. Rods perceive blacks, whites, and grays, but not colors. They detect general shapes. Rods are used for night vision and peripheral vision. High concentrations of rods at the outer portions of the retina act as motion detectors in your child’s peripheral or side vision. 

The receptor cells in the retina send nerve messages about what your child sees to the optic nerve. The optic nerves extend from the back of each eye and join together in the brain at the optic chiasm. From the optic chiasm, the nerve signals travel along two optic tracts, and eventually to the occipital cortex where vision is processed and perceived.

The blood vessels in a developing baby begin to grow during the third month of pregnancy and finish developing by the time of normal birth. Babies that are born prematurely may not have fully developed blood vessels in their retinas. Premature babies are at risk for ROP if the blood vessels grow abnormally. The blood vessels may break and bleed. In turn, scar tissue may develop that can cause retinal detachment. Retinal detachment can reduce vision or result in blindness.

Many premature infants are able to attain healthy retinal blood vessel growth. However, a small percentage of premature infants develop more severe retinal problems. The smallest premature babies, regardless of gestational age, have the highest risk for ROP.

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Symptoms

There may be few signs that ROP is developing. ROP may cause leukocoria, a condition in which the pupil turns white. ROP may cause abnormal eye movements, crossed eyes, or severe nearsightedness.

It is important to have babies that are born prematurely screened by an ophthalmologist. The examination is painless. Eyedrops are placed in the infant’s eyes so that the doctor may view the retinas. The examinations are conducted about every two weeks. 

Laser therapy or cryotherapy may be used to treat areas of the retina that do not have normal blood vessels or to reattach the retina. Cryotherapy uses cold temperatures to destroy abnormal blood vessels. Laser therapy uses high-energy light to eliminate abnormal blood vessels. These are both very short procedures.   

The majority of premature infants with mild ROP experience good recoveries. Children with visual problems from ROP may benefit from rehabilitation and vision aids. Because a possible outcome is blindness, early detection and early treatment are vital.