Saturday, February 2, 2008

Eye Cancer – A Fatal Disease!

The eye collects light and turns it into electronic messages that are sent to the brain. The brain then turns those signals into a picture. As we have two eyes, two pictures are created. Hence if vision of one eye is lost, still other eye continue to do almost everything as before.

The eye has three main parts: the eyeball, the orbit, and the adnexal structures.


EYEBALL

The eyeball is filled with a jelly-like substance called vitreous. The uvea and the retina are two important parts of the eyeball.

The uvea is made up of the iris, the choroid and ciliary body.

 The iris, the colored part surrounding the pupil, controls the amount of light that enters the eyeball.
 The choroids, a thin-pigmented layer inside the eyeball, take care of the retina and the front of the eye with blood.
 The ciliary body have muscles inside the eye that change the shape of the lens for eye to focus on near or distant objects and cells that produce liquid in the eye.

The retina is like the film in a camera. It is in the back of the eyeball and contains cells that are sensitive to light. Cancers affecting the eyeball are called intraocular (within the eye) cancers.

Intraocular cancers are of two types: 1) Primary Intraocular Cancers and 2) Secondary Intraocular Cancers.

1) Primary Intraocular Cancers

Primary Intraocular Cancers are cancers that start inside the eyeball. Melanoma is the most common primary intraocular cancer in adults, followed by primary intraocular lymphoma. In children, retinoblastoma (a cancer arising from cells in the retina) is the most common primary intraocular cancer, and medulloepithelioma is the next most common.

Intraocular Melanoma of iris

If melanoma starts in the iris, it may look like a dark spot on the iris. They arise on the pigmented spot that has been present for many years and then begins to grow. These melanomas are comparatively slow growing, and they rarely spread to other parts of the body. Due to these reasons, people with iris melanomas generally have a good chance of surviving.

Intraocular Melanoma of ciliary body or choroid

If melanoma is in the ciliary body or the choroid, a person may have blurry vision or may have no symptoms, and the cancer may grow fast, even before it is noticed. Approximately 90% of intraocular melanomas occur in the choroids and remaining 10% mostly occurs in the iris. Choroids contain pigment cells called melanocytes. These cells and their product "melanin" absorbs any extra light which might distort the retinal picture. Melanocytes are the cells, which can lose control, and grow into a malignant melanoma. This type of melanoma is usually found during a routine eye examination, when a doctor looks inside the eye with special instruments. The chance of recovery depends on the size and cell type of the cancer; which part of the eye has cancer; and whether the cancer has spread.

Intraocular melanomas are further divided into two types, based on the shape of the cancer cell, they are: 1) Spindle Cell Melanomas and 2) Nonspindle Cell melanomas. Spindle cell melanomas are formed by elongated (stretched out) cells. Nonspindle cell melanomas are formed by epithelioid (round or oval) cells or by a mixture of spindle and epithelioid cells. Nonspindle cell tumors are more difficult to treat successfully as these tumors are more likely to spread to distant sites and be fatal.

Primary Intraocular Lymphoma (Lymphoma of the Eye)

Lymphoma is a type of cancer that generally starts in lymph nodes, which are bean-sized collections of immune system cells. Lymphomas can also start in internal organs such as the stomach, lungs, and rarely in the eyes. There are 2 main categories of lymphoma, they are: Hodgkin disease and non-Hodgkin lymphoma. Primary intraocular lymphoma is always a non-Hodgkin lymphoma. Most people with primary intraocular lymphoma are elderly or have immune system problems such as AIDS.

Retinoblastoma

Retinoblastoma is a relatively uncommon tumor among children that arises in the retina. Although retinoblastoma may occur at any age, in most cases it is diagnosed before the age of 5 years.

Retinoblastoma was one of the first cancers, which is recognized as "hereditary". It can occur in one eye (unilateral) or in both eyes (bilateral). Retinoblastoma is a tumor that occurs in germline and sporadic forms. Germline disease includes those patients with positive family history (i.e. hereditary disease). Most unilateral disease is sporadic or nongermline, whereas all children with bilateral disease have the germline form. Germline tumors tend to occur at a younger age than sporadic tumors.



The treatment of retinoblastoma, depend on the spread, or stage, of the tumor. Retinoblastoma is usually confined to the eye, and thus, more than 90% of children can be cured. Retinoblastoma can be treated by surgery (enucleation), chemotherapy, cryotherapy, light coagulation, and radiation.


Medulloepithelioma

Medulloepithelioma is a very rare tumor that usually occurs in young children. Most medulloepitheliomas are malignant, though they rarely spread. They usually cause eye pain and decreased vision. A biopsy, a procedure in which cells from the tumor are removed and examined under a microscope, is performed to confirm the diagnosis. Treatment is with surgery. The doctor normally tries to remove only the tumor. If that is impossible, then the eye removal is the only option.


2) Secondary Intraocular Cancers

Secondary Intraocular Cancers are cancers that spread to the eye from another part of the body. The most common cancers spreading to the eye are breast and lung cancers. This occurs when cancer become widespread. Usually these cancers spread to the part of the eyeball called the uvea.


ORBIT

The second major part of the eye, the orbit, consists of the tissues surrounding the eyeball. These tissues include muscles that make the eyeball move in different directions and the nerves attached to the eye. Cancers of these tissues are called orbital cancers.


ADNEXAL STRUCTURES

The eyelids and tear glands are adnexal (or accessory) structures. Cancers that develop in these tissues are called adnexal cancers.

Orbit cancer and adnexal cancer develop from tissues such as muscle, nerve, and skin. American Cancer Society consider these cancers as cancer of muscle, nerve, skin, etc. Thus, cancer of eyelid is considered as a skin cancer like other skin cancers.

1 comment:

Medical Information said...

Intraocular melanoma is a type of eye cancer. It is very rare cancer, but it is noticed widespread. It originates in the middle of the three layers of the wall of the eye. Those who have green/blue eyes, elders are more likely to get affected. If anyone notices its symptoms, should immediately consult doctor. For more information on it, refer Intraocular melanoma