How Retinoblastoma Is Diagnosed

Retinoblastoma can only be diagnosed by a qualified clinician, usually an ophthalmologist (medical eye doctor).

Ophthalmologists use several diagnostic tools to determine whether a patient has retinoblastoma, including an ophthalmic (eye) examination, imaging, and blood tests. Sometimes they also perform genetic testing to determine if the retinoblastoma was inherited or occurred spontaneously.

This article will provide an overview of the different methods ophthalmologists use to diagnose retinoblastoma, signs of retinoblastoma you may notice at home, and other potential diagnoses.

A pediatrician checking an 8 month old baby's eyes with a penlight

sdominick / Getty Images

Self-Checks/At-Home Testing

Sometimes parents notice signs and symptoms in their children that concern them, such as trouble with vision, crossed eyes, bulging or irritated eyes, an enlarged pupil, or a white pupil. These symptoms cannot effectively be assessed at home.

What If I Notice a White Pupil?

A white pupil is often discovered when a flash photograph is taken and the pupil appears white in the photo instead of red or black. In retinoblastoma, a white pupil is the result of light reflecting off the white surface of the tumor.

It is important to note that, based on angle and lighting, not every photo will necessarily reveal a white pupil, even if the subject has retinoblastoma or another eye condition.

For this reason, even a single photo of this nature warrants a doctor's visit, especially since retinoblastoma is usually curable if caught early.

It is important to report any changes in vision or the appearance of the eye to a doctor right away. These observations can inform the doctor on what type of exam and tests will be necessary and how much time might be needed for the visit. They may also help the doctor gauge the urgency of an appointment.

Keep in mind that all these signs are simply clues that could also indicate an eye injury or another disease and not a retinoblastoma diagnosis. Only formal examinations by an ophthalmologist can yield a proper diagnosis.

Physical Examination

A complete eye examination (fundoscopy) will provide the most accurate diagnosis of any eye condition, including retinoblastoma. Although most eye exams are simple office procedures, an ophthalmologist usually performs this particular exam under general anesthesia. During the exam dilating drops are used and the eye is kept open with metal clips. The doctor scans the retina for cancer using a light and a magnifying lens.

Instead of, or in addition to, a standard vision test, the doctor may use an electroretinogram to measure electrical activity within the retina. This test measures the electrical sensitivity of the retinal cells. To look for physical abnormalities, the ophthalmologist gently manipulates parts of the retina using a cotton swab and/or a flat-tipped tool called a metal scleral indenter. A medical assistant will typically take photographs of the retina or create diagrams for post-exam evaluation.

During the physical exam, the doctor may ask whether any family member has had retinoblastoma, other cancers, or other abnormalities of the eye. It is a good idea to be prepared with this information at the visit.

Some doctors may examine other areas of the body for masses or unusual appearance. They may ask questions about whether the patient has had any vomiting, headaches, persistent pain, unusual fatigue, dizziness, changes in appetite, or other issues, in order to rule out metastasis (spread) of the suspected cancer to other parts of the body.

Labs and Tests

The doctor will order blood and urine tests to look for evidence of disease—or lack of evidence—and to look for any indications that disease has traveled to areas beyond the eye. They will look at blood counts, measure electrolytes, enzymes, and possibly screen for tumor markers. They will also usually run genetic testing if retinoblastoma is suspected, in order to identify inherited or spontaneous mutations that cause the disease.

Many doctors will also test bone marrow tissue and order a spinal tap (also called a lumbar puncture), in which a needle draws the cerebrospinal fluid from the spinal canal for diagnostic testing.

Examples of tests your care team may run to make a diagnosis include:

  • Complete blood count (CBC): This standard blood test measures red blood cells and hemoglobin, which carry oxygen throughout the body; white blood cells, which mainly fight infection; and platelets,which help blood to clot and bleeding to stop.
  • Blood protein testing (globulin test): This is done through electrophoresis (a laboratory technique that separates charged molecules) to scan for any abnormal proteins from the immune system (immunoglobulins) that might indicate disease.
  • Tumor marker tests: These detect chemicals that are often made by tumors but that can also exist in the absence of cancer.
  • Circulating tumor cell tests: This test detects cells that may have broken off from a tumor.


Ultrasound, also known as sonography, can determine whether retinoblastoma is present and take measurements of any tumors that are found.

Ultrasound works by using high-frequency sound waves to create pictures of the entire eye. The ultrasound technician (sonographer) will numb the eye and then place the wand (transducer) on the eyeball and gently move it along the surface. The procedure is usually painless. After an ultrasound, the doctor may also examine any still photos that were taken during imaging.

To confirm the diagnosis and check that no tumors have metastasized to the brain, the medical team will also sometimes order magnetic resonance imaging (MRI) of the head. The MRI uses a computer along with magnetic field radio waves to create detailed images of the eyes, the brain, and other areas of the head.

Diagnostic Outcomes

If a diagnosis is made early and treatment begins right away, patients can usually survive retinoblastoma and avoid vision loss in at least one eye, possibly both. In addition, early detection and intervention usually mean the cancer is caught before metastasis occurs. Without treatment, however, retinoblastoma is almost always fatal.

Most children who have been treated for retinoblastoma are still alive five years after treatment. After five years without evidence of disease, they are considered cured. Nine out of 10 children with retinoblastoma are completely cured, an outcome that is considerably more likely with early diagnosis.

Can Retinoblastoma Come Back?

Recurrence is always a possibility with cancer. For those who inherited the disease from parents, recurrence is more likely but is not a certain outcome.

Differential Diagnosis

Asking questions of the diagnosing doctor, or even getting a second opinion, is good practice. Sometimes what seems to be retinoblastoma is not, and a specialist who sees a particular disease day in and day out tends to make assumptions about what is familiar. Getting an accurate diagnosis means getting accurate treatment.

If the diagnosis of retinoblastoma is not made, the symptoms could point to other retinal tumors. One such tumor is astrocytic hamartoma, although these are exceedingly rare. Alternatively, some of the same signs and symptoms that lead parents and doctors to suspect cancer could be the result of injury or another eye disease, including:

  • Cataracts (clouding of the normally clear lens of the eye)
  • A detached retina (retina separates from the blood vessels providing it with oxygen and nutrients)
  • Retinopathy due to premature birth
  • Vitreous hemorrhage (bleeding in the tiny fibers surrounded by gel in the eye)
  • Toxocariasis (a parasitic infection)
  • Myelinated retinal nerve fibers (lesions on the retina)
  • Choroidal coloboma (structural defects of the eye)
  • Coats' disease (an eye disorder characterized by abnormal blood vessel development in the retina)

It's important to document all signs and symptoms and to not self-diagnose. What seems like a minor observation to most people might be a major clue to a physician.


Retinoblastoma is a rare eye cancer that appears almost exclusively in young children. Tools for diagnosing retinoblastoma include ophthalmic examination, imaging such as MRIs and ultrasounds, and blood tests. If your healthcare team thinks that retinoblastoma was inherited by a family member, they may also perform genetic testing.

Survivors of retinoblastoma have an increased risk for other cancer types, so vigilance and screenings are important. This is both due to genetic mutations and to treatments such as chemotherapy and radiation that save lives but may also damage DNA.

A Word From Verywell

A cancer diagnosis can be overwhelming. Feelings of fear, helplessness, anger, depression, and despair are common. Retinoblastoma is nobody's fault. Instead, focus on getting a thorough diagnosis and optimal treatment. Caregivers and patients can cope better physically and emotionally with sufficient sleep, a healthy diet, fresh air, and exercise. Support groups, therapy, or a network of supportive family and friends can also be important.

6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Cleveland Clinic. Retinoblastoma (cancer of the eye).

  2. Stanford Medicine. Fundoscopic/ophthalmoscopic exam.

  3. Fabian ID, Onadim Z, Karaa E, et al. The management of retinoblastomaOncogene. 2018;37(12):1551-1560. doi:10.1038/s41388-017-0050-x

  4. American Cancer Society. Tests for retinoblastoma.

  5. Siegel, RL, Miller KD, Fuchs HE, et al. Cancer Statistics 2021. CA Cancer J Clin. 2021. doi:10.3322/caac.21654

  6. American Cancer Society. Treating retinoblastoma.

By Jennifer Leavitt
Jennifer Leavitt, MS, is a health advocate, award-winning writer, and editor who empowers readers with evidence-based information.