How to Diagnose Retinoblastoma

Retinoblastoma is a rare eye cancer that occurs almost exclusively in young children. It can only be diagnosed by a qualified clinician, usually an ophthalmologist (medical ophthalmologist).

Ophthalmologists use a variety of diagnostic tools to determine whether a patient has retinoblastoma, including ophthalmologic (eye) exams, imaging, and blood tests. Sometimes they also do genetic testing to determine whether retinoblastoma is inherited or spontaneous.

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

Self-test / home test

Sometimes parents notice signs and symptoms in their child that are related to them, such as vision problems, strabismus, bulging or inflamed eyes, dilated or white pupils. These symptoms cannot be effectively assessed at home.

What if I notice a white pupil?

White pupils are usually found when a flash photo is taken and the pupil appears white in the photo instead of red or black. In retinoblastoma, the white pupil is the result of light reflecting off the white surface of the tumor.

It’s important to note that, depending on the angle and light, not every photo will necessarily show white pupils, even if the subject has retinoblastoma or other eye disease.

For this reason, even a single photo of this nature requires a doctor’s visit, especially since retinoblastoma is often curable if caught early.

It is important to report any changes in vision or the appearance of your eyes to your doctor immediately. These observations can inform doctors what types of exams and tests are necessary and how long a visit might take. They can also help doctors assess the urgency of an appointment.

Remember, all of these signs are just clues and may also indicate an eye injury or other disease, not a diagnosis of retinoblastoma. Only a formal examination by an ophthalmologist can make a correct diagnosis.

physical examination

A complete eye exam (ophthalmoscopy) will provide the most accurate diagnosis of any eye disease, including retinoblastoma. Although most eye exams are simple office procedures, ophthalmologists usually perform this special exam under general anesthesia. Use dilating eye drops during the exam and keep your eyes open with metal clips. Doctors use lights and a magnifying glass to scan the retina for cancer.

How long will my pupils be dilated after an eye exam?

As an alternative to or in addition to standard vision tests, doctors can use electroretinography to measure electrical activity within the retina. This test measures the electrical sensitivity of retinal cells. To look for physical abnormalities, ophthalmologists use cotton swabs and/or flat tools called metal scleral indenters to gently manipulate parts of the retina. Medical assistants often take pictures of the retina or create charts for post-exam evaluations.

During the physical exam, your doctor may ask if any family members have retinoblastoma, other cancers, or other eye abnormalities. It’s a good idea to have this information ready when you visit.

Some doctors may check other parts of the body for lumps or unusual appearances. They may ask patients if they have any vomiting, headache, persistent pain, unusual fatigue, dizziness, changes in appetite, or other problems to rule out suspected cancer metastasis (spread) to other parts of the body.

Labs and Testing

Doctors will order blood and urine tests to look for evidence of disease — or lack thereof — and to look for any signs that the disease has spread beyond the eye. They will look at blood cell counts, measure electrolytes, enzymes, and possibly screen for tumor markers. If retinoblastoma is suspected, they also usually do genetic testing to identify the inherited or spontaneous mutation that causes the disease.

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

Examples of tests your care team may perform to diagnose 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 clot and stop bleeding.
  • Blood protein test (globulin test): This is done by electrophoresis (a laboratory technique that separates charged molecules) to scan the immune system for any abnormal proteins (immunoglobulins) that may indicate disease.
  • Tumor marker tests: These test for chemicals that are usually produced by the tumor but may be present in the absence of cancer.
  • Circulating tumor cell test: This test detects cells that may be shed from the tumor.

What are tumor markers?


Ultrasound, also called a sonogram, can determine the presence of retinoblastoma and measure any tumors found.

Ultrasound creates an image of the entire eye by using high-frequency sound waves. A sonographer (ultrasound technician) will numb the eye, then place a rod (sensor) on the eyeball and move it gently along the surface. The procedure is usually painless. After the ultrasound, the doctor may also review any still pictures taken during the imaging.

To confirm the diagnosis and to check that no tumor has metastasized to the brain, medical teams sometimes also order magnetic resonance imaging (MRI) of the head. MRI uses a computer and magnetic field radio waves to create detailed images of the eyes, brain, and other areas of the head.

diagnostic result

If diagnosis is made early and treatment is started immediately, patients can often survive retinoblastoma and avoid vision loss in at least one eye, possibly both. In addition, early detection and intervention often means that cancer is detected before metastasis occurs. However, retinoblastoma is almost always fatal if left untreated.

Most children treated for retinoblastoma are still alive five years after treatment. After five years with no evidence of the disease, they were considered cured. Nine out of 10 children with retinoblastoma were completely cured, a result that is more likely to be achieved when diagnosed early.

Can retinoblastoma come back?

There is always a chance that the cancer will come back. For those who inherited the disease from a parent, relapse is more likely, but not a certain outcome.

Differential diagnosis

It’s good practice to ask questions of the diagnosing doctor, or even get a second opinion. What sometimes looks like retinoblastoma isn’t, and experts who see a particular disease day in and day out tend to make assumptions about what’s familiar. Getting an accurate diagnosis means getting the right treatment.

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

  • cataract (clouding of the normally clear lens)
  • Detachable retina (the retina is separated from the blood vessels that supply it with oxygen and nutrients)
  • Retinopathy due to premature birth
  • Vitreous hemorrhage (bleeding in the tiny fibers of the eye surrounded by gel)
  • Toxocariasis (parasitic infection)
  • Myelinated retinal nerve fibers (retinopathy)
  • Choroidal Defects (Structural Defects in the Eye)
  • Coats disease (an eye disorder characterized by abnormal development of retinal blood vessels)

It is important to document all signs and symptoms and not to self-diagnose. What appears to be a secondary observation to most people may be the doctor’s primary clue.


Retinoblastoma is a rare eye cancer that occurs almost exclusively in young children. Tools for diagnosing retinoblastoma include eye exams, imaging (such as MRI and ultrasound), and blood tests. If your medical team believes retinoblastoma is inherited by a family member, they may also do genetic testing.

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

VigorTip words

A cancer diagnosis can be overwhelming. Feelings of fear, helplessness, anger, depression, and hopelessness are common. Retinoblastoma is not anyone’s fault. Instead, focus on obtaining a thorough diagnosis and optimal treatment. Caregivers and patients can better cope with the mind and body through adequate sleep, healthy eating, fresh air, and exercise. Support groups, therapy, or a network of supportive family and friends are also important.

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