Ocular Oncology

Introduction

An eye cancer is a cancer which starts in the eye or starts in the other site of body and affects the eye. There are different types of eye cancers. To understand eye cancers, it is essential to know about the normal structure and function of the eye.

Ocular anatomy

The eye has 3 major parts as far as the cancer is concerned: the eyeball (globe), the orbit, and the adnexal structures.

The cancer can affect the retina, choroid, eyelids and other structures. These cancers are called as intraocular cancers.

Two types of cancers can be found in the eye:

1. Primary intraocular cancers – they start inside the eyeball. In adults, melanoma is the most common primary intraocular cancer, followed by primary intraocular lymphoma. In children, retinoblastoma (a cancer arising from the cells in the retina) is the most common primary intraocular cancer, and medulloepithelioma is the next most common type.

2. Secondary intraocular cancers – they start somewhere else in the body and then spread to the eye. These are not truly eye cancers, but they are actually more common than primary intraocular cancers. The most common cancers spreading to the eye are breast and lung cancers. Most often these cancers spread to the part of the eyeball called as the uvea.

Some important types of orbital cancers include:

1. Intraocular melanoma (melanoma of the eye)

Melanomas develop from pigment-making cells called melanocytes. These cancers are also called as uveal melanomas. About 9 out of 10 intraocular melanomas develop in the choroid (which is part of the uvea). Nearly all of the remaining intraocular melanomas start in the iris (also part of the uvea). They start as a pigmented spot on the iris that has been present for many years and then begins to grow. They rarely spread to other parts of the body and have a good prognosis.

2. Primary intraocular lymphoma (lymphoma of the eye)

Eye cancer is uncommon, and therefore there is no widely recommended screening test for this cancer in people.

Lymphoma is a type of cancer that starts in immune system cells called as lymphocytes. It usually starts in lymph nodes, which are bean-sized collections of immune system cells scattered throughout the body.

There are 2 main types of lymphoma: Hodgkin disease and non-Hodgkin lymphoma. Primary intraocular lymphoma is always a non-Hodgkin lymphoma. Most people with this tumour are elderly or have the acquired immunodeficiency syndrome (AIDS). Primary intraocular lymphoma can often occur along with primary central nervous system lymphoma.

3. Retinoblastoma – this is tumour of retina occurring in infants and young children. It presents as strabismus, a whitish or yellowish glow through the pupil, loss of vision, sometimes the eye may be red and painful. Any children with photos showing a white/yellow dot instead of the red eye reflex should be checked out.

4. Benign tumours – Orbital dermoid cysts are typically found at the junction of embryonic sutures, most commonly at the fronto-zygomatic suture. Large dermoid cysts can exert pressure effects on the muscles and optic nerve, leading to diplopia and loss of vision. Nevus is also a benign tumour. They should be checked out regularly to ensure that it hasn’t turned into a melanoma.

5. Orbital and adnexal cancers

Cancers of the orbit and adnexa develop from tissues such as muscle, nerve, and skin around the eyeball and are like their counterparts in other parts of the body. An example of this type is Rhabdomyosarcoma (muscle cell tumour)

Screening of eye cancer:

Eye cancer is uncommon, and therefore there is no widely recommended screening test for this cancer in people. Screening is testing for a disease like cancer in people without any symptoms. In some cases, eye cancer can be found early. Some doctors may recommend yearly eye examination for those who are at higher risk of eye melanoma, such as people with dysplastic nevus syndrome.

Treatment:

There are various treatments for ocular cancers. They include:

1. Laser therapy to destroy tumour calls

2. Plaque therapy

3. Radiotherapy

4. Enucleation of the Eye – Removal of the eye, but the muscles and eyelids are left intact. An implant is inserted and the person wears prosthetic or an artificial eye.

5. Evisceration – Removal of the eye contents, leaving the sclera or the white part of the eye.

6. Exenteration – Removal of the eye, all orbital contents, which can involve the eyelids as well. A special prosthesis is made to cover the defect.

7. Iridectomy – Removal of the affected part of the iris

8. Choroidectomy – Removal of the choroid layer (the vascular tissue between the sclera and the retina)

9. Iridocyclectomy – Removal of the iris and the ciliary body muscle.

10. Eyewall resection – Cutting into the wall of the eye to remove a tumor such as melanoma. This operation can be quite difficult to perform.

11. Chemotherapy