n WHAT IS RETINOBLASTOMA? Retinoblastoma is a cancer of one or both eyes which usually occurs in children who are younger than 5 years of age. The tumor(s) occur in the retina (the innermost layer of the eyeball), which is the area of the eye containing nerves that control vision. Retinoblastoma is the most common intraocular (eye) child- hood cancer and has an excellent prognosis, with a greater than 95% cure rate if the disease is contained within the retina when diagnosed. There are 2 forms of retinoblastoma, unilateral (one eye involved) and bilateral (both eyes involved). The majority of patients (60%) have unilateral disease and are diagnosed between 18 and 36 months of age. The remaining 40% of patients have bilateral tumors and are usually diagnosed at a younger age (often during the first year of life and rarely after 2 years of age). STRUCTURE AND FUNCTION OF THE EYE It is helpful to know the names, locations, and functions of the structures of the eye to understand your child’s tumor. The eye has three layers with a total thickness of about ¾-inch (in a child) from front to back: • Sclera: the white outer covering that protects the eye • Choroid: the middle layer, which contains the blood vessels that bring nourishment to the eye • Retina: the inner layer, which contains the nerves that send messages to the brain for sight. Other structures of the eye include the following: • Cornea: the clear portion at the front of the eye through which light rays pass • Conjunctiva: a thin membrane that lines the outside of the eye • Iris: the colored part of the eye • Pupil: the black opening in the middle of the iris that allows light into the eye • Lens: the area behind the iris and pupil that focuses light onto the retina • Vitreous humor: a gel-filled chamber of the eye that nourishes the eye and gives it shape • Macula: the part of the retina that provides central vision • Optic nerve: the nerve that carries messages from the eye to the brain. n WHAT ARE SOME OF THE SYMPTOMS OF RETINOBLASTOMA? The most common signs of retinoblastoma are leukocoria and strabismus. Leukocoria is often called “cat eye reflex”. It is a white reflection (similar to a cat’s eye in the evening) seen in the pupil (black portion of the eye) when light shines in a child’s eye, instead of a red reflection (a red glow in dim light that is com- monly seen in flash pictures). Strabismus is a wandering eye, or abnormal turning in or out of the eye, that does not go away. Other less common symptoms are changes in vision, eye irritation, and pain. When these symptoms are present, your child also may rub his or her eye frequently or have redness of the eye and tearing, along with vomiting.
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