Retinoblastoma

Retinoblastoma - (Reh-tin-oh-blast-oma)

• Retinoblastoma is a rare, cancerous tumor of a part of the eye called the retina

• Retinoblastoma - (Reh-tin-oh-blast-oma) is a cancer of one or both eyes which occurs in young children. There are approximately 350 new diagnosed cases per year in the United States. Retinoblastoma affects one in every 15,000 to 30,000 live babies that are born in the United States. Retinoblastoma affects children of all races and both boys and girls
• The retinoblastoma tumor(s) originate in the retina, the light sensitive layer of the eye which enables the eye to see. When the tumors are present in one eye, it is referred to as unilateral retinoblastoma, and when it occurs in both eyes it is referred to as bilateral retinoblastoma. Most cases (75%) involve only one eye (unilateral); the rest (25%) affect both eyes (bilateral). The majority (90%) of retinoblastoma patients have no family history of the disease; only a small percentage of newly diagnosed patients have other family members with retinoblastoma (10%).

 

• The eye of an adult measures about one inch from the front to the back of the eye; a child's eye measures about three-quarters of one inch.

• The eye has three layers:

1. Sclera - the outer protective white coating of the eye

2. Choroid - the middle layer which contains blood vessels to nourish the eye

3. Retina - the inner layer which contains the nerves that bring information to the brain for     seeing

• The cornea is the clear portion of the front of the eye which bends light rays. 
• The conjunctiva is a thin tissue which lines the eyelids and the eyeball up to the edge of the cornea. 
• The iris is the colored portion of the eye which is made up of a spongy tissue and is an extension of the choroid. 
• The pupil is the opening in the iris (black) which allows light into the eye.
• The lens helps focus light rays onto the retina the way a camera lens focuses light onto film; the lens can change shape, or accommodate, to focus on near or distant objects.
• The eye is filled with fluids which help nourish and maintain the pressure within the eye. The anterior chamber, the front portion of the eye between the iris and the cornea, is filled with aqueous humor, a watery fluid which nourishes the lens and mantains the pressure within the eye. 
• The back portion of the eye is filled with vitreous humor, a transparent gel.
• The retina is made up of ten layers and contains over one million cells.
• The optic nerve has nerve fibers which transmit information to the brain for interpretation of objects seen.
• The macula is the area of the retina that is responsible for central vision; its central portion is referred to as the fovea and is responsible for the sharpest vision.
• The macula houses the highest concentration of the cones which are responsible for color and sharp vision. 
• The rods, which compose the rest of the retina, are more sensitive to light and are responsible for night vision and peripheral vision. 
• Attached to the globe of the eye are six muscles which aid in the movement of the eye. Movement of the eye may be caused by one, a few, or all of the muscles working together. 
• Causes, incidence, and risk factors 
• Retinoblastoma is caused by a mutation in a gene controlling cell division, causing cells to grow out of control and become cancerous.
• In a little over half of the cases, this mutation develops in a child whose family has never had eye cancer.
• Other times the mutation is present in several family members. If the mutation runs in the family, there is a 50% chance that an affected person's children will also have the mutation. They will therefore have a high risk of developing retinoblastoma themselves.
• The cancer generally affects children under the age of 6. It is most commonly diagnosed in children aged 1 - 2 years.
  Symptoms 
• One or both eyes may be affected.
• The pupil may appear white or have white spots. 
• A white glow in the eye is often seen in photographs taken with a flash. Instead of the typical "red eye" from the flash, the pupil may appear white or distorted.
• Other symptoms can include
• Crossed eyes
• Double vision
• Eyes that do not align
• Eye pain and redness
• Poor vision
• Differing iris colors in each eye
• If the cancer has spread, bone pain and other symptoms may occur.
  Signs and testsThe health care provider will perform a complete physical exam, including an eye exam. The following tests may be done:
• Bone marrow biopsy and cerebrospinal fluid examination in the case of more aggressive tumors
• CT scan or MRI of the head
• Eye exam with dilation of the pupil
• Ultrasound of the eye (head and eye echoencephalogram)
  
  Treatment 
• Treatment options depend on the size and location of the tumor.
• Small tumors may be treated by laser surgery or cryotherapy.
• Radiation is used for both local tumor and for larger tumors.
• Chemotherapy may be needed if the tumor has spread beyond the eye.
• The eye may need to be removed (a procedure called enucleation) if the tumor does not respond to other treatments. In some cases, it may be the first treatment.
  Expectations (prognosis) 
• If the cancer has not spread beyond the eye, almost all patients can be cured. A cure, however, may require aggressive treatment and even removal of the eye in order to be successful.
• If the cancer has spread beyond the eye, the likelihood of a cure is lower and depends on how the tumor has spread.
  Complications
  Blindness can occur in the affected eye. The tumor can spread to the eye socket through the optic nerve. It may also spread to the brain, lungs, and bones.
  Prevention
  Genetic counseling can help families understand the risk of retinoblastoma. It is especially important when more than one family member has had the disease, or if the retinoblastoma occurs in both eyes.
• sources : http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0002025/
• sources : http://retinoblastoma.com/retinoblastoma/frameset1.htm