Before a child is born (while still in the womb), the eyes begin to develop.
Anatomy of the Eye
From the anatomy of the eye above, the retina can be easily identified as the innermost layer of the eye, located at the back of the eye. The retina receives light and images necessary for vision. Retinoblasts are rapidly growing cells in the eye which eventually mature to form the retina.
Retinoblastoma occurs when these cells form a tumour on the retina as they fail to stop reproducing. These tumours may be endophytic, when they keep growing inwards to fill up the vitreous humour, and can break off to float in the vitreous, and may be exophytic when they grow and spread outwards to other parts of the eye and outside the eye, to lymph nodes and other organs. In some cases, there is a combination of both.
Retinoblastoma is the most common intraocular cancer found in childhood. It is a rare, malignant tumour of the retina of one or both eyes that occurs in under-5 children. Diagnosis of retinoblastoma is made usually within the first four years of life, mostly between 18 and 24 months. In 60-70% of case it occurs unilaterally (occurs in one eye), and in 30-40% of cases it is bilateral (occurs in both eyes). In certain instances, it is trilateral, occurring in both eyes with a pineoblastoma. It affects all races and both sexes. It affects 1 in every 15,000 to 20,000 live births.
Retinoblastoma may be sporadic or secondary to a germline mutation of the Retinoblastoma tumour suppressor gene which is inherited. Children of retinoblastoma survivors have a 45% chance of having retinoblastoma.   
Symptoms of retinoblastoma experienced by each child differ, but the most common include:
Eye pain, Red eye(s), Swelling of the eye(s), Poor vision, Strabismus (wandering eye, where the eyes do not align when they ought to look in the same direction) and Leukocoria (a white light reflex instead of the normal red reflex when a light is shone on the pupil).
Diagnosis of retinoblastoma is made after a comprehensive eye examination including a dilated funduscopy by the eye doctor. Other tests done to confirm diagnosis and determine the stage of the tumour and its spread include:
Ultrasound – use of sound waves to create images of tissues
Magnetic Resonance Imaging (MRI) – use of magnets, radiofrequencies, and a computer to produce detailed images of organs and structures within the body without the use of X-rays
Computed Tomography Scan (CT/CAT Scan) – use of X-rays and computer technology to produce axial images of the body, including bones, muscles, fats and organs
Spinal Tap (Lumbar Puncture)
Bone marrow tests
Blood tests
Genetic and/or DNA testing
Treatment for retinoblastoma is determined by a number of factors. These include the stage of the cancer at the time of diagnosis; the child’s age, health and medical history; and the child’s tolerance for specific medications and procedures. Retinoblastoma is a highly curable condition, but early diagnosis portends better outcomes. The prognosis (outcome of treatment) depends on the size and location of the tumour; the spread of the tumour; the tumour’s response to therapy; the age and health of the child; and the child’s tolerance of specific medications and therapies.
Treatment may include
Photocoagulation (Laser therapy): The use of laser to kill blood vessels that feed the tumour
Cryotherapy: The use of freezing process to destroy cancer cells.
Thermal therapy: The use of heating process to destroy cancer cells.
Chemotherapy: The use of medication (oral –swallowed through the mouth, intravenous –injected into the vein, or intrathecal –injected into fluids surrounding the brain and spinal cord) to kill or slow down the growth of multiplying cancerous cells
Radiation therapy: The use of X-rays (external-beam radiation therapy) to destroy cancer cells, or the placing of radioactive material inside of or near the tumour (local/internal radiation therapy) to destroy cancer cells.
Enucleation: The surgical removal of the eye(s) affected by the tumour to save the child’s life.
The goal of treatment for retinoblastoma is to get rid of the cancer and save the child’s life; to save the eye if possible; to preserve as much vision as possible; to limit the risk of second cancers, which may be caused by treatment, especially in children with hereditary retinoblastoma
Close follow-up after treatment till the child is 4 or 5 is important to prevent reoccurrence in hereditary retinoblastoma. Since those with hereditary retinoblastoma are at higher risk for new cancers later in life than those with sporadic retinoblastoma, it is advised that they have regular medical and eye exams (at least once a year).