If a doctor sees outward signs of retinoblastoma, the next steps will be an eye exam under general anesthesia, CT scan, ultrasound, or MRI of the retina. Once a diagnosis of retinoblastoma is made, doctors will conduct more tests to determine whether cancer has spread, including, possibly a bone scan, a bone marrow biopsy, or a spinal tap. Doctors will also do genetic testing to see if your child's retinoblastoma is the type that can be passed down in a family.