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Diagnosing eye cancer
Diagnosis is the process of finding the cause of a health problem. The process of diagnosis may seem long and frustrating, but it is important for the doctor to rule out other reasons for a health problem before making a cancer diagnosis. Diagnostic tests for eye cancer are usually done when:
- the symptoms of eye cancer are present
- routine eye examination suggests a problem with the eye
Many of the same tests used to initially diagnose cancer are used to determine the stage (how far the cancer has progressed). Your doctor may also order other tests to check your general health and to help plan your treatment. Tests may include the following.
The medical history is a record of present symptoms, risk factors and all the medical events and problems a person has had in the past. The medical history of a person’s family may also help the doctor to diagnose eye cancer.
In taking a medical history, the doctor will ask questions about:
- a personal history of
- existing eye conditions – primary acquired melanosis or ocular melanocytosis
- skin moles
- HIV infection or AIDS
- exposure to sunlight or use of indoor tanning devices
- possible occupational exposure (such as welding)
- signs and symptoms that may suggest eye cancer
An eye (ophthalmic) examination allows the doctor to check vision, assess the health of the eyes and look for any signs of eye cancer. An eye examination is done by an eye specialist (ophthalmologist). They examine the eyes by doing a series of tests with different instruments, such as:
- ophthalmoscope – a lighted instrument with a small microscope
- slit lamp – a microscope with a light attached to it, which provides a more detailed view of the inside of the eye
- gonioscope – a special lens that examines the front part of the eye to check for glaucoma
- transillumination – a special lighted instrument is placed on the eyelid to examine a tissue by passing a strong beam of light through it
- optomap (retinal imaging) – an examination of the retina using a digital retinal scanning system that creates images of most of the retina
- optical coherence tomography (OCT) – a type of imaging test that uses light waves to take cross-sectional pictures of the retina, which allows doctors to see the layers within the retina and measure the thickness of the retina
Drops may be put in the eyes to enlarge (dilate) the pupil, which helps the doctor see structures inside the eye better. During an eye examination, the doctor may:
- look at the different structures of the eye to check for abnormalities
- check the front and back of the eye
- look for enlarged blood vessels on the surface of the eye
- check eye movement
Ultrasound uses high-frequency sound waves to make images of structures in the body. An ultrasound of the eye and orbit is used to:
- confirm a diagnosis of eye cancer
- find out the location and size of the tumour
- An ultrasound can determine the size of larger eye tumours, but is not as useful for evaluating smaller tumours.
- see how far the tumour extends beyond the eye
- check the features of the tumour
- Eye melanomas have a specific appearance on ultrasound.
Drops are sometimes used to numb the eye before the ultrasound is done, or ultrasound can be done without eye drops. The ultrasound probe is gently placed over closed eyelids or on the surface of the eye.
Two types of ultrasound may be used to examine the eye (ophthalmic ultrasound) – ultrasound A and B. Both are used to determine the size, features and extent of an eye melanoma. They are also used to find out if the eye tumour is a metastasis from another part of the body.
- Ultrasound A scans provide a one-dimensional view of the eye. They are mainly done to measure the length of the eye.
- Ultrasound B scans provide a cross-sectional, 2-dimensional view of the inside of the eye.
An ultrasound of the liver may also be done if the doctor suspects that the eye cancer (such as an eye melanoma) has spread to the liver.
Fluorescein angiography is a procedure used to x-ray blood vessels inside the eye. A special dye called fluorescein is used to make blood vessels in the eye visible on the x-ray. Drops are first given to enlarge (dilate) the pupil of the eye. Then the dye is injected into the arm and travels to the blood vessels in the eye. A series of pictures are then taken to:
- see if there are any blockages, leaks or bleeding (hemorrhage) within the eye
- find out more about the features of a tumour
- help rule out eye problems other than cancer
A similar test, indocyanine green angiography (ICG), uses a special green dye to look at the blood vessels in the retina. This procedure is useful for detecting disease in the choroid of the eye.
During a biopsy, tissues or cells are removed from the body so they can be tested in a laboratory. The pathology report from the laboratory will confirm whether or not cancer cells are present in the sample.
Unlike most other cancers, which need a biopsy to confirm the diagnosis, cancers within the eye can usually be diagnosed by an eye examination and imaging. A biopsy is not needed in many cases and doctors tend to avoid taking a biopsy from the eye itself. It can be difficult to get a sample of the tumour without damaging the eye and possibly spreading the tumour. A biopsy can be taken from accessory (adnexal) structures outside the eye, such as the eyelid.
However, intraocular lymphoma cannot be diagnosed with an eye examination and imaging, so a biopsy is usually required.
The biopsies that may be used for eye cancer are:
- fine needle aspiration
- A fine needle aspiration (FNA) may be done to diagnose an eye tumour, particularly in cases that are difficult to diagnose. A very thin needle and syringe are used to remove (aspirateaspirate1. Accidentally sucking or breathing food or fluid into the lungs. 2. A procedure that uses a needle to withdraw or remove cells, fluid or tissue. For example, a small amount of bone marrow is withdrawn from the hip bone through a needle during bone marrow aspiration.) a small number of cells from the suspected tumour.
- vitreous biopsy
- A vitreous biopsy (vitrectomy) is a procedure in which a very small cut is made and then a fine needle is inserted into the jelly-like vitreous humor inside the eye to remove a sample.
- If the vitreous humor is cloudy, a biopsy may be done to find out if there are any lymphoma cells present or if the cloudiness is a result of a non-cancerous (benign) condition.
A CT scan uses special x-ray equipment to make 3-dimensional and cross-sectional images of organs, tissues, bones and blood vessels inside the body. A computer turns the images into detailed pictures. It is used to:
- determine the size of the eye tumour, especially for extraocular tumours (tumours that have spread beyond the eye)
- find out how far the tumour extends beyond the eye
- find out if the cancer has spread to other parts of the body
- A CT scan may be used to stage eye cancer that has spread to distant parts of the body, such as the liver.
MRI uses powerful magnetic forces and radio-frequency waves to make cross-sectional images of organs, tissues, bones and blood vessels. A computer turns the images into 3-dimensional pictures. It is used to:
- determine the size of the eye tumour
- find out the extent of the tumour and if the optic nerve is involved
- see if the cancer has spread to other parts of the body
- MRI may be used to stage an eye cancer that has spread outside the orbit of the eye, or to the brain or spinal cord.
Blood chemistry tests measure certain chemicals in the blood. They show how well certain organs are functioning and can also be used to detect abnormalities. Some blood chemistry tests are used to help stage eye cancer.
- Increased lactate dehydrogenase (LDH), alanine aminotransferase (ALT) and aspartate transaminase (AST) may indicate that the eye cancer has spread to the liver.
An x-ray uses small doses of radiation to make an image of the body’s structures on film. A chest x-ray may be done to find out if an eye cancer (such as melanoma of the eye) has spread to the lung.