Retinoblastoma is a rare eye cancer that develops in the retina, the light-detecting tissue at the back of the eye. This disease primarily affects very young children, with most cases diagnosed before the age of two. While the diagnosis of cancer in a child can be deeply frightening for families, advances in treatment have made survival rates remarkably high in countries with access to specialized care, and many children preserve their vision or learn to adapt to changes in sight.

How Common Is Retinoblastoma?

Retinoblastoma is quite uncommon. In the United States, approximately 250 to 300 children are diagnosed with this eye cancer each year.^[6] When looking at the broader picture, about 3.3 cases occur per 1 million people under the age of 20, which translates to slightly under 9,000 new cases worldwide annually.^[2] The disease represents about 3% of all cancers that affect children younger than 15 years old.^[4]

This cancer occurs in one eye in approximately 60% of cases, a condition called unilateral retinoblastoma. The remaining 40% of cases affect both eyes, known as bilateral retinoblastoma.^[2] The vast majority of children—four out of five—are diagnosed before they reach their third birthday, and more than 90% of cases are found by age five.^[4][7] Boys and girls are equally affected by this disease.^[6]

While retinoblastoma most often appears in infants and toddlers, there are rare instances where it develops in older children or even adults. In these unusual cases, the tumor may have paused its early development before resuming growth later in life.^[2]

What Causes Retinoblastoma?

Retinoblastoma develops because of changes in a specific part of a child’s genetic material. These changes occur in a gene called RB1, which is located on chromosome 13.^[1] In healthy conditions, the RB1 gene acts like a set of instructions that tells cells when to stop growing and dividing. When this gene malfunctions, cells in the retina can multiply uncontrollably, forming a tumor.^[2]

The genetic instructions inside our cells work much like recipes in a cookbook. If there is an error in the recipe, the cells can only follow the incorrect instructions, which may cause them to grow and behave abnormally. In retinoblastoma, both copies of the RB1 gene in a retinal cell must be damaged for a tumor to form, since everyone has two copies of this gene—one from each biological parent.^[8]

There are two main types of retinoblastoma based on how and when these genetic changes occur. The first type is hereditary retinoblastoma, which accounts for about 40% of cases.^[8] In these children, one copy of the faulty RB1 gene is either inherited from a parent or develops in the egg or sperm just before or after conception. This means the child is born with one RB1 mutation already present in every cell of their body. When a second mutation happens later in the cells of the retina, tumors can form. Children with hereditary retinoblastoma often develop multiple tumors and are more likely to have cancer in both eyes.^[9] They also face an increased risk of developing other types of cancer later in life, including tumors in the bones, soft tissues, or brain.^[7]

The second type is called non-hereditary retinoblastoma or sporadic retinoblastoma, which makes up about 60% of cases.^[8] In this situation, both copies of the RB1 gene become damaged by chance after birth, and only in cells of the retina. Children with non-hereditary retinoblastoma typically develop a tumor in just one eye, and they generally do not pass the genetic change on to their own children in the future. These children also do not have the same elevated risk for other cancers that children with hereditary retinoblastoma face.^[7]

Risk Factors for Retinoblastoma

The most significant risk factor for developing retinoblastoma is having a family history of the disease. If a parent or sibling has been diagnosed with retinoblastoma, a child is more likely to inherit the faulty RB1 gene.^[9] Because of this, children with a known family history of retinoblastoma should undergo regular eye examinations shortly after birth and throughout early childhood to catch any tumors as early as possible.^[10]

However, it is important to note that most children who develop retinoblastoma do not have a family history of the condition. In these cases, the genetic mutation occurs spontaneously, meaning it happens by chance rather than being passed down through generations.^[7]

Signs and Symptoms of Retinoblastoma

Because retinoblastoma most often affects babies and toddlers who cannot yet describe what they are experiencing, parents and caregivers usually notice visible changes in the child’s eyes or behavior. The earliest and most common sign is called leukocoria, which means “white pupil.” When light shines into the affected eye—such as when taking a photograph with a flash—the pupil may appear white, pale, or yellowish instead of showing the normal red reflection seen in healthy eyes.^[1][2] This white glow is sometimes referred to as “cat’s eye reflex” and can be particularly noticeable in photos taken in dim lighting.^[5]

Another common symptom is strabismus, which is when the eyes do not appear to be looking in the same direction. One or both eyes might seem to be turning inward toward the nose or outward toward the ear, a condition often called “crossed eyes” or “wandering eye.”^[6][7] Some children may also have trouble following movement with their eyes, or their eyes might not follow movement at all.^[2]

Less common symptoms can include redness or swelling of the eye, pain or discomfort that may cause a baby to cry more than usual or have trouble sleeping and feeding, or a pupil that looks larger than normal. In more advanced cases, the eye itself may appear larger or may bulge forward, a condition known as proptosis.^[2] Occasionally, there may be blood visible in the front part of the eye, called hyphema.^[2]

Any unusual appearance of a child’s eyes or changes in vision or behavior should prompt a visit to a healthcare professional. Early detection greatly improves the chances of successful treatment and preserving vision.^[1]

Prevention of Retinoblastoma

Because retinoblastoma is caused by genetic mutations that occur either before birth or very early in life, there are no known lifestyle changes, dietary measures, or environmental modifications that can prevent the disease from developing. It is not caused by anything a parent did or did not do during pregnancy or after the child was born.^[1]

However, early detection is critical and can significantly improve outcomes for affected children. For families with a history of retinoblastoma, genetic counseling and testing can help determine whether a child is at risk of inheriting the condition. If a hereditary risk is identified, pediatricians and eye specialists can conduct regular, careful eye examinations starting shortly after birth. These screenings allow doctors to detect tumors when they are still small, which often means that less aggressive treatments are needed and the child has a better chance of keeping their vision.^[10][13]

Parents and caregivers should also be vigilant for any signs of retinoblastoma, such as a white reflection in the pupil in photographs, crossed eyes, or other unusual changes in the appearance or behavior of the eyes. Bringing these concerns to a doctor’s attention as soon as they are noticed can lead to earlier diagnosis and treatment.^[1]

How Retinoblastoma Affects the Body

Retinoblastoma begins in the retina, which is a thin layer of nerve tissue lining the inside back wall of the eye. The retina is responsible for sensing light and sending visual signals through the optic nerve to the brain, where those signals are interpreted as images.^[1] When retinoblastoma develops, immature retinal cells called retinoblasts begin to grow out of control because of the damaged RB1 gene. Instead of developing into healthy, functional retinal cells, these abnormal cells multiply rapidly and form a tumor.^[8]

The tumor can grow in different patterns. Some tumors grow inward toward the center of the eye into the gel-like substance called the vitreous humor, a pattern known as endophytic growth. Others grow outward, lifting the retina away from the back of the eye in a pattern called exophytic growth. In some cases, the tumor exhibits a combination of both patterns.^[4] As the tumor expands, it can cause pieces of itself to break off and float inside the eye, a process called seeding.^[4]

If left untreated, the tumor can invade deeper structures of the eye. It may spread into the choroid, a layer of blood vessels beneath the retina, or into the optic nerve, which connects the eye to the brain. Once the tumor reaches these areas, there is a risk that cancer cells can travel through the bloodstream or along nerve pathways to other parts of the body, a process known as metastasis.^[4] In advanced cases, the tumor may even break through the outer wall of the eye and spread into the surrounding tissues of the eye socket, or it may reach the brain or other organs.^[5]

The physical changes caused by retinoblastoma can interfere with vision. Depending on the size and location of the tumor, a child may experience partial or complete loss of sight in the affected eye. The tumor can also cause increased pressure inside the eye, leading to pain and discomfort.^[2] In cases where the disease is caught early and confined to the eye, the outlook is generally very good, with high survival rates and often preservation of useful vision.^[7]