The human eye is filled with a viscous jelly like fluid known as vitreous humor. This viscous fluid fills up the space between the front and the back of the eye. The front section of the eye contains the lens that play the role of a camera shutter for the eye. The lens directs the light to the back of the eye that contains the retina which is a thin layer of special nerve cells that exhibit sensitivity to light. The nerve cells are connected to the brain through the back of the eyeball via the optical nerve. During the first trimester of pregnancy, the eyes of the baby develop early. The small cells known as retinoblasts form the retina and, grow and divide into new cells. The expansion and division of retinoblasts stop once the retina is formed with mature retinoblasts. However in certain babies, the cells continue to divide even after the retina is formed completely, leading to the condition, Retinoblastoma.
Cause and Symptoms
Retinoblastoma is essentially an uncontrolled expansion of retinoblasts in the retina of certain babies. The cause is associated with a mutation in the RB1 gene that keeps a check on the division of retinoblasts. The mutation is known as germline mutation. Children afflicted with retinoblastoma are susceptible to tumors in pineal gland of the brain. The cause of this mutation is largely unknown, despite its association with hereditary and genital aspect at the time of birth. If not treated, the cancer cells can spread into the vitreous humor and spread to other parts of the eyes leading to ocular tumors and visual impairment. Children affected by retinoblastoma exhibit a white colour in their pupil center. Their eyes may appear squinted and cross-eyed and, show signs of redness and swelling in their eyes.
Diagnosis involves a thorough examination of the affected eye through imaging tests like ultrasound, MRI and CT scan. The consulting team includes a counsellor, an ophthalmologist, a lab technician and an oncologist. The diagnosis of the condition gives the doctor an insight into the size, spread and the malignity of the tumour in the eye. The baseline reports aid in deciding the course of treatment that would mitigate side effects of the treatment.
Chemotherapy involves administering drugs orally or, by injecting them into the blood vessel. The chemo drugs aid in shrinking the tumors and culling the cancer cells that divide at a highly accelerated rate. In children, if chemotherapy effectively removes the tumors, the surgery can be avoided. Radiation therapy is yet another effective means of treating retinoblastoma in children, that uses high energy X ray beams. If internal radiation therapy is engaged, a treatment disk made of radioactive material is stitched in the affected region. The disk emits radiation that culls the tumor and, protects the healthy tissue in the eye from cancer cells. If external radiation therapy is used, high powered beams are focussed on the tumor from outside the body. However, this therapy is recommended only for children suffering from advanced retinoblastoma. If the tumor is deep set in the retina, Laser therapy is used to destroy the blood vessels connecting the tumor. Temperature based treatments such as Cryotherapy and Thermotherapy aid in treating retinoblastoma effectively. Cryotherapy uses liquid nitrogen to freeze the cancer cells at the site of treatment. A few rounds of freezing and thawing the cancer cells alternatively kills them. Thermotherapy on the other hand, uses extreme heat in the form of lasers and microwave beams to kill the cancer cells.
In children with an advanced retinoblastoma that has resulted in a huge tumor, surgical means like enucleation is adopted. Enucleation is a surgical process in which, the muscles and tissue around the eye are disconnected and, the eyeball is entirely removed along with a section of the optical nerve. The removal of the section of optical nerve reduces the chances of the cancer spreading into the brain. Post surgery, a conformer made of silicone (a plastic disc) is placed into the socket to prevent the socket from shrinking until the artificial eye is made and placed in the socket. Post four to six weeks of healing, an eye implant procedure is performed. A special artificial eye ball made of plastic, silicone or glass, is fitted into the eye socket along with the removed muscles and tissue. It takes a while for the child to adapt to the usage of the artificial eye. Although it may not help much with the sight, it surely makes up for the cosmetic appearance in the child. Professional ocularists perform the procedures of making and fitting the artificial eye appropriately into the socket.
Dr. Debraj Shome is a highly acclaimed oculoplastic surgeon in India. He has specialised in a variety of oculoplastic surgeries that have involved oncology. Currently, he is the head of Plastic Surgery Dept of Nova Specialty Surgery in Mumbai.