Retinoblastoma is a rare type of eye malignancy that starts from the immature retina cells, the eye’s light-detecting tissue. This tumor is almost exclusively found in children, with the highest incidence in children under 5. In children, it can affect either one or both eyes. Nearly half of the children with this disease have a hereditary gene defect. However, other causative reasons have also been identified.
Based on the region of localization of the tumor, it is broadly classified as:
- · Intraocular retinoblastoma – Cancer is completely localized within the eye.
- · Extraocular retinoblastoma – Cancer spreads beyond the eye to other body parts.
This tumor is often curable if diagnosed early. But, if it is not appropriately treated, it can fill up the entire Eyeball, metastasize to other parts of the body, and even be life-threatening.
Causes
Mutations in the RB1 and MYCN genes of the nerve cells in the retina give rise to retinoblastoma. A mutation occurs on chromosome 13 of the RB1 gene in children with a heritable form of this tumor. These mutations can be inherited from the parents or in the early stages of fetal development. Such mutations cause bilateral retinoblastoma. Besides RB1 inactivation, another reason behind this tumor is the increased production of the MYCN gene that, in turn, promotes cell proliferation. This oncogene is responsible for some non-hereditary, early-onset, aggressive, unilateral retinoblastoma cases.
Symptoms of Retinoblastoma
The symptoms of retinoblastoma are:
- · Visible whiteness in the Pupil (cat’s eye reflex or leukocoria)
- · Crossed eyes or eyes that do not point in the same direction (strabismus)
- · Change in the color of the iris
- · Redness, soreness, or swelling of the eyelids
- · Blindness or poor vision of the affected eye or eyes
- · Red or irritated eye with glaucoma
- · Eyeball is larger than normal
- · Pupil looks cloudy
- · Infection around the eye
Screening tests
The diagnosis begins with a general physical examination enabling the physician to understand the symptoms better. A detailed eye exam is conducted to rule to look into the inside of the eye, including the retina and the optic nerve. Other screening tests recommended for its confirmation include:
- Ø Computed tomography (CT) scan uses X-rays to determine the size of the retinoblastoma tumor and the extent to which it has spread.
- Ø Eye ultrasound: High-frequency sound waves are used to produce eye images and are widely used to confirm if the child has retinoblastoma. It is also used when the tumors in the eye are huge and prevent the doctors from seeing inside the whole eye.
- Ø Fluorescein angiography: An orange fluorescent dye called fluorescein is injected intravenously. It travels to the eyes via the blood vessels. Flash pictures of the blood vessels in and around the tumor are taken every few seconds using a special camera to identify areas in the eye that are blocked or leaking.
- Ø Electroretinography: Light and small electrodes are used to study the retina and assess its function before and after treatment.
- Ø RB1 gene test: A blood or tissue sample is taken and tested to detect any changes in the level of the RB1 gene.
- Ø MRI scan: Radio waves and strong magnets are used to create detailed images of the eye and surrounding structures.
Treatment of Retinoblastoma
The following approaches are used for treating retinoblastoma:
- Chemotherapy – Chemotherapeutic drugs are used to kill cancer cells or shrink the tumor, so other treatment methods may be used to kill them. They can be administered systemically or intra-arterially to deliver the medicine directly to the tumor via an artery supplying blood to the eye.
- Radiation therapy – High-powered beams such as gamma rays or protons are used to kill cancer cells. It is delivered to the tumor by placing a radioactive plaque directly over the tumor in the eye.
- Transpupillary thermotherapy or laser therapy – Heat destroys the tumor cells.
- Cryotherapy – Tumor cells are frozen by placing them near a freezing substance like liquid nitrogen and then removed and thawed. This process is repeated till all the cancerous cells die.
- Surgery is recommended for treating big retinoblastoma tumors that other methods cannot treat. Enucleation (removal of the eye and part of the optic nerve), followed by surgery to place an eye implant to compensate for the removed Eyeball, is one part of the surgical procedure. As this implanted Eyeball cannot see, a custom-made artificial eye is placed over it several weeks after the surgery. This artificial eye sits between the eyelids and can move like usual but will not impact lost vision.
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