According to a study the rare form of eye cancer- Retinoblastoma which generally occurs in children under age of 5 goes undetected or is detected at a very late stage in India. It is found in one in 15,000 live births in India.
To understand what is Retinoblastoma first let us understand the structure of the human eye.
Human eye is made up of three layers- namely Sclera, Choroid and Retina. The various parts of an eye are as follows:
- Sclera: It is the outer coat of the eye that forms the visible white part of the eye. Its main function is to provide structure, strength, and protection to the eye.
- Choroid: The middle layer between the retina and sclera is called the choroid. It is pigmented layer. The choroid contains blood vessels that supply the retina with nutrients and oxygen and removes its waste products.
- Retina: The retina is the inner layer of cells in the back of the eye. It is made up of specialized nerve cells that are sensitive to light. It is the light sensitive part of the eye. It consists of rods and cones. Rods are good for monochrome vision in poor light, while cones are used for colour and for the detection of fine detail. When light strikes either the rods or the cones of the retina, it is converted into an electric signal that is sent to the brain via the optic nerve. The brain then translates the electrical signals into the images we see.
- Cornea: The outer most layer Sclera continues as Cornea in front. It is transparent layer and helps to focus incoming light.
- Iris: Choroid continues to from Iris. It is coloured. The amount of light entering into eye is regulated by contraction or expansion of the muscles of iris, which controls the size of pupil.
- Pupil: The iris has an adjustable circular opening called the pupil, which can expand or contract depending on the amount of light entering the eye
- Lens: The lens is the clear structure located behind the pupil. Its primary function is to provide fine-tuning for focusing and reading. The lens performs this function by altering its shape
- Ciliary Muscles: Ciliary muscles surround the lens. The muscles hold the lens in place but they also play an important role in vision. When the muscles relax, they pull on and flatten the lens, allowing the eye to see objects that are far away. To see closer objects clearly, the ciliary muscle must contract in order to thicken the lens.
- Aqueous humor: There is space between the cornea and the lens, it is known as anterior chamber. It is made up of liquid known as aqueous hum. It nourishes the cornea and the lens and exerts pressure so that shape of lens is maintained.
- Vitreous Body: This is the clear gel-like substance located inside the eye’s cavity. Its purpose is to provide a spherical shape to the eye
What is Retinoblastoma?Retinoblastoma is an eye cancer that begins in the retina – the sensitive lining on the inside of our eye. Retinoblastoma most commonly affects young children, but can rarely occur in adults.
It is a rare form of eye cancer, and is the most common form of cancer affecting the eye in children. Retinoblastoma may occur in one or both eyes.
How does retinoblastoma develop?The eyes develop very early as babies grow in the womb. During the early stages of development, the eyes have cells called retinoblasts that divide into new cells and fill the retina. At a certain point, the cells stop dividing and develop into mature retinal cells. Rarely, something goes wrong with this process. Instead of maturing into special cells that detect light, some retinoblasts continue to divide and grow out of control, forming a cancer known as retinoblastoma.
The chain of events that leads to retinoblastoma is complex, but it almost always starts with a change (mutation) in a gene called the retinoblastoma (RB1 or Rb) gene.
The normal RB1 gene helps keep cells from growing out of control, but the change in the gene stops it from working like it should.
Types of Retinoblastoma:
- Intraocular Retinoblastoma: Does not spread beyond the eye.
- Extra ocular Retinoblastoma: Cancer spreads beyond the eye to the other body parts such as brain.
Symptoms of Retinoblastoma:
- A cloudy white colour in the centre of the eye (pupil) or white reflex.
- Poorly aligned or ‘wandering’ eye, also known as squinting of eyes
- Painful reddish pupil
- Larger than normal pupil
- Different coloured irises
- Decreased Vision
The type of treatments depends on the size and location of the tumor, whether cancer has spread to areas other than the eye or it is limited to eye.
- Chemotherapy is a drug treatment that uses chemicals to kill cancer cells. Chemotherapy can be taken in pill form, or it can be given through a blood vessel. Chemotherapy drugs travel throughout the body to kill cancer cells.
- In children with retinoblastoma, chemotherapy may help shrink a tumor so another treatment, such as radiation therapy, cryotherapy, thermotherapy or laser therapy, may be used to treat the remaining cancer cells.
- Chemotherapy may also be used to treat retinoblastoma that has spread to tissues outside the eyeball or to other areas of the body.
- Radiation therapy:
- Internal radiation (brachytherapy): During internal radiation, the treatment device is temporarily placed in or near the tumor. Internal radiation for retinoblastoma uses a small disk made of radioactive material. The disk is stitched in place and left for a few days while it slowly gives off radiation to the tumor. Placing radiation near the tumor reduces the chance that treatment will affect healthy eye tissue.
- External beam radiation:External beam radiation delivers high-powered beams to the tumor from a large machine outside of the body. External beam radiation can cause side effects when radiation beams reach the delicate areas around the eye, such as the brain. For this reason, external beam radiation is typically reserved for children with advanced retinoblastoma and those for whom other treatments haven’t worked.
- Laser therapy:
- Cold treatments (cryotherapy): Cryotherapy uses extreme cold to kill cancer cells. During cryotherapy, a very cold substance, such as liquid nitrogen, is placed in or near the cancer cells. Once the cells freeze, the cold substance is removed and the cells thaw. This process of freezing and thawing, repeated a few times in each cryotherapy session, causes the cancerous cells to die.
- Heat treatments (thermotherapy): Thermotherapy uses extreme heat to kill cancer cells. During thermotherapy, heat is directed at the cancer cells using ultrasound, microwaves or lasers.
- Surgery to remove the affected eye (enucleation). During surgery to remove the eye, surgeons disconnect the muscles and tissue around the eye and remove the eyeball. A portion of the optic nerve, which extends from the back of the eye into the brain, also is removed.
- Surgery to place an eye implant. Immediately after the eyeball is removed, the surgeon places a special ball made of plastic or other materials in the eye socket. The muscles that control eye movement are attached to the implant. After sometime the eye muscles will adapt to the implanted eyeball, so it may move just as the natural eye did. However, the implanted eyeball cannot see.
Cases of Retinoblastoma in India:
- Retinoblastoma usually which develops in early childhood, typically before the age of five, is found in one in 15,000 live births in India.
- The eye cancer could be cured if detected in the early stage, however due many barriers, ranging from poor awareness to inadequate economic resources result in late detection of eye cancer in children.
- The medical advice of chemo therapy, radiation and removal of eye prompt the parents of children to abandon the treatment.
- In some cases the parents live in the myth that the deformity of their child will bring luck.
- According to ophthalmologist due to the lack of documentation in national cancer registries there is poor collection of data related to cases of eye cancer. Therefore the true magnitude of the problem is largely unknown.