The short answer
For melanoma inside the eye, the tumor's height and base width decide the options. Radiation that spares the eye is preferred for most medium tumors, but NCI is blunt that sight in the treated eye is often lost over time.
The Collaborative Ocular Melanoma Study set the size bands NCI still uses: small is 1.0 to 3.0 mm high, medium 3.1 to 8.0 mm, large over 8.0 mm or a base over 16.0 mm.
For most people with a medium tumor, NCI describes radiation that spares the eye, by plaque or external beam, as the preferred option — though where the tumour sits and how your sight already is can change that.
Removing the eye stays standard for large tumors, and when the tumor causes severe glaucoma or grows into the optic nerve.
A plaque is a small disc of radioactive seeds sewn to the outside of the eye, and NCI says iodine 125 is probably the most common isotope.
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The full explanation.
Size and position drive the choice
For melanoma inside the eye, the tumor's height and the width of its base are measured first. NCI's checklist also records where it sits: the iris, the ciliary body, or the choroid at the back.
The Collaborative Ocular Melanoma Study set the size bands NCI still uses. Small means 1.0 to 3.0 mm in height with a base of 5.0 to 16.0 mm. Medium means 3.1 to 8.0 mm in height with a base no wider than 16.0 mm. Large means over 8.0 mm in height, or a base over 16.0 mm when the height is at least 2.0 mm.
Ask for your numbers in millimetres. Ask which band they put you in.
What that band means for treatment
NCI is direct about medium tumors. Radiation that spares the eye, given by plaque or by external beam, is the preferred option for most people.
For large tumors, NCI describes removing the eye as the standard option. NCI also names it as standard when the tumor causes severe glaucoma or grows into the optic nerve.
The list for medium tumors is longer than many people expect. Plaque radiation. Charged-particle beam radiation at specialist centres. Removal of part of the eye wall. Plaque treatment combined with laser. Removal of the eye, mainly for spread outside it.
How the plaque works
A plaque is a small disc of radioactive seeds sewn onto the outside of the eye. NCI lists the isotopes used, and says iodine 125 is probably the most common.
It is honest about the trade. Plaque radiation lets you keep the eye, but sight in that eye is often lost over time.
Ask what your sight is likely to be at one year and at five.
Testing the tumor while treating it
This section, like the rest of the page above the retinoblastoma note, is about adult uveal melanoma.
NCI's pathology checklist includes a gene expression profile reported as class 1 or class 2. It also records chromosome results, especially loss on chromosome 3.
These can come from a biopsy, including a fine needle sample. Whether that is possible, and whether it is done at the same sitting as your treatment, depends on where the tumour sits, how thick it is and what the centre is equipped for, so it is a question for the ocular oncologist rather than something to expect. It does not carry across to retinoblastoma, where biopsy is generally avoided because of the risk of spreading tumour outside the eye.
For a child with retinoblastoma
Retinoblastoma is a different disease with different aims, and nothing above this heading applies to it. The size bands, the plaque decisions and the biopsy question all come from adult uveal melanoma. Ask which treatments could save the eye and the sight, ask about genetic testing for the child and the family, and ask to be seen at a centre that treats this cancer often. Ask the team directly before agreeing to any tissue sampling, since biopsy of a retinoblastoma can spread tumour beyond the eye and is generally avoided.
Questions for the eye cancer visit
- How tall is my tumor, and how wide is the base?
- Is it small, medium or large by those measures?
- Where does it sit, and how close is it to my optic nerve?
- Which options are open to me, and what does each cost my sight?
- Will I keep useful vision in that eye?
- For a uveal melanoma, is a biopsy for the gene and chromosome tests possible in my case, and would it be at the same sitting as treatment?
- How often will this eye be checked afterwards, and by whom?
Related pages
Cancer Staging and Biomarker Testing explain the terms used in an eye cancer treatment discussion. Clinical Trial vs Standard Treatment, Palliative Care, and Questions to Ask Your Doctor help you prepare for the eye cancer appointment itself.
Where this comes from
These questions were drawn from current patient guidance for eye cancer (uveal melanoma; retinoblastoma in children):
Words to know
Tap any term to see what it means.
Common questions
If I keep my eye, will I keep my sight?
Not always. NCI says plaque radiation lets you keep the eye, but sight in that eye is often lost over time. Ask what your vision is likely to be at one year and at five.
What counts as a medium tumor?
Medium means 3.1 to 8.0 mm in height with a base no wider than 16.0 mm. Ask for your height and base in millimetres, and ask which band they put you in.
Can the tumor be tested without a second procedure?
Often yes. The gene and chromosome tests can come from a biopsy, including a fine needle sample. Ask whether it can be taken at the same sitting as your treatment.
Is eye cancer in a child treated the same way?
No. Retinoblastoma is a different disease with different aims. Ask which treatments could save the eye and the sight, and ask to be seen where this cancer is treated often.
Questions to ask your doctor
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Sources last checked: 2026-07-30 what this meansLast updated: 2026-08-19Next planned review: 2027-07-30
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How this page was created
Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes. We do not employ clinicians and do not intend to — our work is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Editorial review complete — This page completed Cancer Explained's editorial checks (sources, safety, plain language, duplication). It has not been reviewed by a physician or other healthcare professional.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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