It occurs when the blood vessels in the retina do not develop normally in babies who are born prematurely.
Retinopathy of prematurity (ROP) can cause severe vision loss if it is not diagnosed and treated early. A premature baby is born before the due date.
The retina is located at the back of the eye and is a very complex and sensitive structure that is responsible for the initial formation of the visual image. The light image is transferred by the optic nerve to the brain , allowing us to see.
If a baby is born too early, his retinal blood vessels do not develop fully and can cause problems. Abnormal blood vessels can grow outside of the retina and cause scar tissue to form , leading to detachment of the retina.
This damage is known as retinopathy of prematurity, and if not monitored or treated at the right time, it can cause vision loss.
How the eye works
At the front of your eye is a transparent tissue called the cornea, which allows light to enter the eye. Your cornea focuses light through your pupil, which is a hole in the center of your iris, the colored part of your eye.
Behind the iris is your lens, this also focuses the light that enters the cornea. Both the cornea and the lens focus the light that hits your eye onto an area of your retina.
Your retina is at the back of your eye and lines the inside of your eyeball. The retina is made up of several layers, but the most important for vision is the layer made up of cells called photoreceptors .
Photoreceptors are cells that are sensitive to light. When light is focused on the retina, the photoreceptors react and convert the light into electrical signals. When light enters the eye, it is first focused through the cornea and then more precisely through the lens so that it reaches the retina correctly.
The focus that the cornea and lens help make your vision clear and sharp. When light hits the retina, the photoreceptors react to the light that hits them by sending a small electrical charge through the optic nerve to the brain.
Photoreceptors react differently to different levels of light or lighting conditions and this changes the nature of the electrical signals that are sent through the optic nerve.
When the parts of your brain that deal with vision receive these electrical signals, they make sense to them and this gives you the images we call sight. All of this happens so fast that it is almost instantaneous.
Causes of retinopathy of prematurity
The reasons why babies develop ROP are complicated, but ROP is more likely to occur in babies than:
- They are born very prematurely, particularly, with less than 32 weeks of gestation.
- Have a low birth weight of less than 1,500 grams.
- They have needed oxygen treatment.
Premature babies often need extra oxygen, and although it is necessary for the baby’s survival, it can increase the risk of developing ROP.
Not all premature babies who need oxygen develop ROP. Pediatricians monitor the oxygen levels that a baby may need very carefully to ensure that enough oxygen is delivered for the baby’s survival, taking into account the effects this may have on the baby’s eye.
ROP checkups are a regular part of care for all premature babies born before 32 weeks.
Symptoms of retinopathy of prematurity in the eye
ROP mainly affects the blood vessels in the retina. When retinal blood vessel development is incomplete, the retina is not getting enough oxygen so it tries to grow new vessels.
These new vessels are fragile and cause scarring. In rare cases, the more serious forms of ROP, if left untreated, can lead to retinal detachment and blindness. There are a few ways to describe the amount of ROP present including its location, extent, and stage.
The location on the retina is divided into three zones where zone one is the innermost and zone three is the outermost. The zones are not centered around the retina, but rather, the optic nerve. This is because blood vessels tend to grow from the area where the optic nerve exits the eye called the optic nerve disc.
The ROP extension is described using clock hours. For example, if retinopathy is present from 6:00 to 9:00, the extent of ROP is three clock hours.
Generally speaking, there are five stages of ROP. These stages describe what the ophthalmologist would see when they look into a baby’s eyes.
The peripheral or outer part of the retina has slight changes that are clearly marked by a demarcation line or a flat white line that divides the abnormal area of lack of blood supply with the normal area. Babies generally recover without any medical treatment.
The damage is still on the periphery and is considered a mild anomaly, but the line of demarcation is raised and looks more like a ridge. Babies generally recover without any medical treatment at this stage as well.
New blood vessels begin to grow on the ridge. These blood vessels are very weak and will cause vision problems if they start to heal. Also, the disease is when the growth of the blood vessels is severe and there is an enlargement and tortuosity of these blood vessels.
This stage of ROP usually requires laser treatment.
The fragile new blood vessels that grow in stage three can contract (shrink) and cause scarring that can pull the retina away from the back of the eye (partial retinal detachment).
The retina can detach completely from the back of the eye (total retinal detachment). This would lead to permanent vision loss. Most premature babies only develop stage one and stage two of ROP, and only a small number develop stage three and need treatment.
Number of premature babies with retinopathy of prematurity
In the UK, more than 60 per cent of babies who have a birth weight of less than 1,251 grams will have ROP.
However, most of these babies (about 94 percent) will have mild ROP that does not require treatment. Only about six percent of premature babies will have advanced ROP that requires treatment.
The incidence of ROP is on the rise as more and more babies now survive when they are born prematurely. This means that there are more babies with ROP. However, advances in the medical treatment of babies mean that fewer babies need treatment.
Treatments are now offered at an earlier stage than in the early 2000s, so severe, sight-threatening forms of ROP (stages four and five) are rare.
Diagnosis of retinopathy of prematurity
All newborn babies weighing less than 3 pounds or 1501 g, or babies born before 32 weeks gestation, will have an eye screening exam. An eye doctor (ophthalmologist) will do the screening and can diagnose ROP.
The eye drops will be placed in the baby’s eyes to enlarge the pupil, which is necessary for the ophthalmologist to see the retina inside the eye clearly. Numbing drops are also used so that the baby does not feel any pain.
The ophthalmologist will use a special lens and light during the exam, which often only takes a few minutes. After the eye exam, the ophthalmologist will decide if treatment is required.
This screening will be done weekly or biweekly until approximately 36 weeks’ gestation when the risk of developing ROP requiring treatment has passed. If a baby has any signs of ROP, these tests will continue beyond 40 weeks.
Treatment for retinopathy of prematurity
Many babies with ROP do not need treatment as it often resolves on its own. If new blood vessels start to grow, laser treatment can be used to prevent further damage.
A baby will need general anesthesia for this treatment, which means that they will be unconscious for the entire treatment to ensure that they are completely immobile and because the treatment is painful while it is occurring.
Treatment uses a laser to make small burns on the retina inside the eye. This can stop the development of new blood vessels.
After the treatment is over, the baby may have eye drops for a week or so, but the eye will no longer be painful. The baby’s eye will need to be examined in about a week to see if the laser treatment has worked. Some babies may need more than one of these treatments.
Another possible treatment option currently being explored for ROP is anti-vascular endothelial growth factor (anti-VEGF). Anti-vascular endothelial growth factor (anti-VEGF) drugs are substances that prevent blood vessels from forming or growing.
However, this treatment requires more research and evaluation before it can be used safely in infants and it is not clear at this time what kind of effects these medications may have on the rest of the baby’s body.
In many babies, early treatment is often successful. This means that the abnormal blood vessels stop developing and a retinal detachment does not occur.
In some babies, treatment can prevent the retina from detaching, but their vision may be affected; They may not regain all of their sight again after treatment.
In a baby with stage four or five ROP, surgical treatment such as a vitrectomy may be performed. A vitrectomy procedure involves removing the vitreous gel in the eye and replacing it with a clear solution.
The fluid holds the detached retina against the back of the eye or the retinal pigment epithelium from the inside.
How will vision be affected?
Babies born earlier are at higher risk for vision problems, which are not caused by ROP, when they grow up. These problems include myopia or myopia and strabismus that can often be corrected with glasses.
Other possible problems, such as damage to the optic nerve or the visual pathway to the brain, cannot be corrected and can lead to permanent vision problems. Vision in children develops from birth to seven years.
Doctors will not be able to say anything about the baby’s vision until at least six weeks after its original due date when the vision turns on. It is often several years before a true idea of the child’s visual potential is possible.
Babies who have stage one and stage two ROP may not have any vision problems and therefore will not require regular eye exams by an ophthalmologist.
Often, stage one and two babies would only have to undergo the national vision test that begins at school age around the ages of four to five. Any future concerns with your eyes or vision would require a referral from an ophthalmologist.
Babies who have stage three ROP can be followed in the clinic according to the center’s protocol as they are more likely to have eye problems. Babies who have been treated will be monitored regularly for myopia and the long-term effects of laser scars that sometimes affect vision.
In babies who are stage four and five, the ROP will have significant vision loss. Although vitrectomy surgery is successful in some of these babies, many have a poor visual outcome.
The number of babies with ROP who require treatment is still very small. There have been great improvements in the screening, diagnosis and treatment of retinopathy of prematurity that has led to better visual outcomes for these children.
How do you react if your baby is diagnosed with retinopathy of prematurity?
If your child is diagnosed with an eye condition, it can be very tricky. You may worry about their future and how they will do it. All of these feelings are natural.
Some people may want to discuss some of these feelings with someone outside of their circle of friends or family. Your GP or social worker can also help you find a counselor if they think this might help.
Your local authority must have at least one qualified teacher of visually impaired children to work with you and your child, both at home and at school. These specialists are qualified teachers who have additional qualifications and experience in working with visually impaired children.