Retinoblastoma, a cancer of the eye, develops in the retina. It mostly occurs in children between 1 to 4 years old. If the disease is diagnosed early, cure rate is as high as 90%.
In about 40% of patients, the tumour involves both eyes. Two eyes may be affected at the same time or one following the other.
The exact cause is not known, but hereditary factors do play an important part in about 40% of cases. Such patients have a high chance of having both eyes involved. The offspring of these patients will also have as high as 50% chance of getting the same disease. About 60% of the cases are sporadic and non-hereditary, and the chance of the offspring of the patients getting the disease is less than 25%.
Two commonest symptoms are squinting and the white pupil reflex (pupil reflecting a white light like a cat's eye). Usually the parents are the first to discover the symptoms as the young child will not be able to complain. The child's eyesight may deteriorate, and his eye may become inflammed. The disease tends to remain localized for long periods, but in advanced stages, it can spread to other parts of the body, such as bones, thus causing bone pain.
The diagnosis is often confirmed by an ophthalmologist after examining the eyes under general anaesthesia. Other tests are computerized tomography scan or magnetic resonance imaging of the head including the eyes and orbits to define the local extent of the disease, chest X-ray, lumbar puncture, as well as bone marrow aspiration, in order to look for possible spread to these sites.
Treatment depends on the size, position and number of tumours in the eye.
Early tumours can be eradicated by burning (photocoagulation) or freezing (cryotherapy) the tumour, or by radiotherapy. Slightly larger tumours are generally treated by radiotherapy. Over 90% of cases can be cured by these treatment processes, and eyesight can usually be preserved.
With large tumours, it may involve removing the entire affected eyeball. In cases where both eyes are affected, every attempt will be made to preserve vision in at least one eye.
If there is evidence of the cancer spreading to other parts of the body, chemotherapy, radiotherapy, or both, may also be used.
Cataracts may develop 18 months to 2 years after radiotherapy, which can be removed surgically. Spectacles or contact lenses prescribed to help correct the vision. Reduced tear production may also develop after radiotherapy. Artificial eye drops can be applied in order to keep the eyes moist so as to prevent infection. After an affected eye is removed, an artificial eye will be fitted. The patients should be examined regularly for any recurrence. Those with tumour in both eyes also have a high risk of developing a second cancer, commonly a bone tumour.
Because there are hereditary factors associated with this disease, genetic counselling will be given. It is also important to have the siblings and offspring of the patients with hereditary retinoblastoma examined regularly in the first 2 years of life to help early detection of disease.