Retinoblastoma is a form of cancer arising in children in their early years. The disease can occur any time from when a child is still in the womb up to the age of about five years. It affects about one in 20,000 children and accounts for about 3% of all cancers for children under the age of fifteen . With retinoblastoma, a tumor develops in the immature retinal cells of the eye, which are the cells responsible for detecting color and light. Without functioning retinal cells, children with this disease can have moderate to severe visual disability if they survive. In developing countries, if the disease is diagnosed and treated early enough, the condition is curable in about 90% of patients. However, in the developing countries, the survival rate is very low.
There are two forms of the disease, hereditary and non-hereditary. In the hereditary form, the retinoblastoma (Rb) gene is missing from chromosome 13 leading to the absence of a functional gene or its protein product. This leads to the presence of multiple tumors in both eyes and is referred to as bilateral retinoblastoma . In the non-hereditary form, only one eye is affected with one tumor and is referred to as unilateral retinoblastoma. The non-hereditary form is considered to be a sporadic mutation of the Rb gene while the hereditary or familial form of the disease is a mutation passed on from one or both parents.
The eye is a very complex structure designed to allow us to see different colors and movement in many different levels of light. The retina is the part of the eye that allows us to see by sending signals to the brain. It is made up ten layers and over a million cells. Retinoblastoma tumors can be presented in a number of different ways. The most common manifestation of the disease is for patients to have a white pupil reflex rather than the normal black one, which is referred to as leukocoria. The abnormal white eye reflex is often referred to as a cat’s eye reflex and is usually noticed by a parent. However, leukocoria may not always indicate retinoblastoma. Another common manifestation of retinoblastoma is a crossed eye or strabismus. This is where the child’s eye either turns in toward the nose or out towards the ear. These are referred to as esotropia and exotropia respectively. Other presentations of the disease include a red eye, inflammation, poor vision, or abnormal irises or pupils. In all these cases, the retinoblastoma gene is mutated and unable to perform its role within the cell.