How Is Eye Cancer Diagnosed

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HealthTree

Last updated and reviewed on: September 30, 2026

For most adults, the path to an eye cancer diagnosis starts somewhere ordinary: a routine visit to an eye doctor. You may have gone in because your vision seemed a little blurry, or simply for your regular checkup, glasses update, or contact lens fitting. During that visit, the doctor put drops in your eyes to dilate (widen) your pupils and looked inside your eye with a bright light. That is often the moment a suspicious pigmented (colored) spot is first found, sometimes for a completely unrelated reason. This guide walks through the tests doctors use to figure out what that spot is. Uveal melanoma (also called intraocular or ocular melanoma) is the most common primary eye cancer in adults, which is the focus of this guide unless stated otherwise.

Because uveal melanoma has no population-wide screening test, most cases are found this way: by chance, during an exam that was not looking specifically for cancer. Some people notice symptoms first, such as blurred vision, floaters, flashes of light, or a dark spot on the iris (the colored part of the eye). Others have no symptoms at all, since a tumor growing in the back of the eye may not affect vision until it has grown fairly large. Either way, the next steps usually look similar: closer examination, imaging, and sometimes referral to a specialist.

Your workup will likely involve more than one type of eye doctor. A general or comprehensive ophthalmologist (a medical doctor who specializes in eye diseases) often makes the first observation. If a lesion looks suspicious, you will usually be referred to an ocular oncologist, an ophthalmologist who focuses specifically on eye tumors and has the experience to tell a harmless spot from a cancer. If tissue is ever removed, either through a small sample or during surgery, an ophthalmic pathologist examines it under a microscope to confirm what it is. This team approach exists because uveal melanoma is rare, and getting the diagnosis right the first time matters enormously for your treatment options and your vision.

Here is the point many patients find most reassuring once they understand it: unlike most other cancers, a biopsy (removing a piece of tissue for lab testing) is rarely needed to diagnose uveal melanoma. Experienced ocular oncologists can accurately diagnose the large majority of uveal melanomas using a careful eye exam combined with imaging tests alone, without ever placing a needle in the eye. This is unusual in cancer care, where a tissue biopsy is almost always the first step. It happens because uveal melanoma has a distinctive appearance on ultrasound and other imaging, and because decades of careful study, including the landmark Collaborative Ocular Melanoma Study, have taught doctors exactly what features separate a melanoma from a benign lesion.

If you are reading this because you are afraid of having a needle placed in your eye, take a breath. For the great majority of people with a suspected uveal melanoma, that fear turns out to be unfounded, because no biopsy is needed at all. When a biopsy is used, it is usually to help guide treatment and estimate risk after the diagnosis is already fairly certain, not to first prove that cancer is present. The rest of this guide explains, in plain terms, what each test involves, what it feels like, and what it tells your doctor, plus what to expect if a pigmented spot found by accident turns out to be a harmless nevus (freckle) rather than a melanoma.

What Tests Are Used to Diagnose Eye Cancer?

Not everyone needs every test described below. Your doctor will choose tests based on where the suspicious area is, how it looks, your symptoms, and your overall health. Most of these tests are quick, done in an office setting, and do not require you to be put to sleep.

Comprehensive Dilated Eye Exam and Indirect Ophthalmoscopy

This is usually the very first step. Your doctor places drops in your eyes to widen (dilate) the pupil, which normally takes about 15 to 20 minutes to take full effect. Once your pupils are dilated, the doctor can see through the lens of your eye all the way to the retina (the light-sensing layer at the back of the eye) and the structures around it, including the choroid, where most uveal melanomas begin.

To get this view, doctors commonly use indirect ophthalmoscopy. You will recline slightly, and the doctor holds a small magnifying lens close to your eye while shining a bright light into it from a handheld instrument worn on their head. It does not hurt, though the light can feel briefly bright or glaring, and your vision will stay blurry for several hours afterward because of the dilating drops. This exam lets the doctor look for a raised or flat pigmented lesion, check its color, and get a first impression of its size and location. Bring sunglasses to your appointment, since dilated eyes are more sensitive to light, and arrange for a ride if you are not comfortable driving while dilated.

Slit Lamp Examination

A slit lamp is a stationary instrument you sit in front of, resting your chin and forehead against supports while the doctor examines your eye through a microscope with a narrow, bright beam of light. It provides much more magnification than a handheld light and lets the doctor closely examine the front structures of the eye, including the cornea (the clear front window of the eye), the iris, and the lens, as well as get a magnified look at the back of the eye when combined with a special lens. The exam itself is painless; you may see bright light and need to hold still for a minute or two while the doctor looks closely at each part of your eye.

Fundus Photography

Fundus photography takes a detailed picture of the inside of your eye, including the retina, the choroid, and the optic nerve. A special camera captures the image while you keep your eye open and still, looking at a target light for a moment. It feels similar to having a regular photograph taken, though the flash can be brief and bright.

The real value of fundus photography is tracking change over time. If your doctor finds a small pigmented spot and is not yet sure whether it is a harmless nevus or an early melanoma, they can take a picture today and compare it to a new picture taken months later. Growth over time is one of the most important clues that a lesion needs closer attention or treatment.

Ocular Ultrasound (A Scan and B Scan)

Ultrasound is one of the most useful tests for diagnosing uveal melanoma, because these tumors tend to have a recognizable appearance on ultrasound images that helps doctors tell them apart from other eye conditions. For this test, numbing eye drops are used, and a small handheld probe is placed gently against your closed eyelid or directly on the numbed surface of the eye. The probe sends out harmless sound waves and picks up the echoes as they bounce off the tissues inside your eye, creating a picture on a screen. It does not hurt, though you may feel light pressure from the probe.

There are two related types. A scan ultrasound measures precise distances and is used to calculate exactly how thick a tumor is, an important number for staging and treatment planning. B-scan ultrasound creates a two-dimensional cross-sectional picture that shows the tumor's shape, such as whether it is dome-shaped, mushroom-shaped, or flat and spread out (called diffuse), and can also reveal fluid collecting under the retina near the tumor. A specialized, higher-resolution version called ultrasound biomicroscopy can look in even finer detail at tumors near the front of the eye, such as those in the iris or ciliary body (the ring of tissue behind the iris that helps focus the eye).

Fluorescein Angiography and Indocyanine Green Angiography

Both of these tests look at the blood vessels inside your eye and how blood flows through them. For fluorescein angiography, an orange fluorescent dye is injected into a vein in your arm. As the dye travels through your bloodstream and reaches the blood vessels in your eye, a special camera takes rapid pictures using a light that makes the dye glow, revealing any vessels that are blocked or leaking. Indocyanine green angiography works the same way but uses a green dye that is especially good at showing the deeper blood vessels of the choroid.

You may feel a brief pinch from the needle and a warm sensation as the dye is injected. Your skin and urine may take on a temporary yellowish or greenish tinge for a day or so, which is harmless. These tests help doctors distinguish a melanoma, which often has an abnormal blood vessel pattern, from other conditions that can look similar, such as certain benign growths or bleeding under the retina.

Optical Coherence Tomography

Optical coherence tomography, usually called OCT, is similar to ultrasound but uses light waves instead of sound waves to create extremely detailed, cross-sectional images of the retina and sometimes the choroid beneath it. You simply rest your chin on a support and look at a target while the machine scans your eye for a few seconds; no dye, needle, or contact with the eye is needed. OCT is especially good at detecting subtle fluid or swelling under the retina near a tumor, which can be an early sign that a pigmented lesion is active rather than dormant.

Transillumination

Transillumination is a simple, low-tech test in which the doctor places a bright light against your closed eyelid, either the upper or lower one, in a darkened room. Because eye tissue is somewhat translucent, the light can help outline the shape of certain tumors and show where they cast a shadow inside the eye, particularly tumors involving the iris or ciliary body. It is painless and takes only a moment.

When Is a Biopsy Used?

As explained above, most uveal melanomas are diagnosed through careful examination and imaging alone, without ever removing a piece of tissue. A biopsy is used selectively, not routinely, mainly in two situations: when the diagnosis genuinely remains uncertain after a full clinical and imaging workup, or when a biopsy is done specifically to gather tissue for genetic testing that helps predict risk (described in the next section), sometimes at the same time as the main treatment.

When a biopsy is needed, the most common method is fine needle aspiration biopsy, in which a very thin, hollow needle is used to withdraw a small sample of cells from the tumor. This can be done through the wall of the eye (transscleral), through the clear gel inside the eye (transvitreal), or through the cornea (transcorneal), depending on where the tumor is located. It may be done with numbing eye drops and a sedative, or under general anesthesia, depending on the situation.

Patients understandably worry about a needle going into the eye, and it is fair to be honest about the risks. One real but small risk is tumor seeding, meaning a few cancer cells could theoretically be carried along the path the needle traveled, potentially spreading outside the eye. Older laboratory studies raised this concern, but large modern clinical series using careful, refined techniques have found this complication to be rare in practice. Reported experience with hundreds of fine needle aspiration biopsies for uveal melanoma has shown very low rates of serious complications such as bleeding, retinal detachment, or tumor spread along the needle track. Your ocular oncologist can walk you through the specific risks and benefits for your situation before recommending a biopsy.

Tumor Genetic Testing After Biopsy or Eye Removal

If tissue becomes available, whether from a biopsy or from surgery to remove all or part of the tumor, doctors can run genetic tests on the tumor cells themselves. This is tumor (somatic) testing, meaning it looks at changes inside the cancer cells, not changes you were born with or could pass on to your children. The goal is not to diagnose the cancer, which has usually already been established by exam and imaging, but to estimate how likely the melanoma is to spread to other parts of the body, most often the liver, and to guide how closely you should be monitored afterward.

One well-established test looks at chromosome 3. Uveal melanomas that have lost one full copy of chromosome 3, a pattern called monosomy 3, tend to carry a higher risk of the cancer spreading later. Doctors may also test chromosomes 6 and 8 for gains or losses that add further prognostic information. Related mutation testing looks at specific genes: changes in the BAP1 gene, located on chromosome 3, are linked with a higher risk of spread, while changes in the SF3B1 or EIF1AX genes tend to be linked with a lower risk.

Another approach is gene expression profiling, which looks at patterns of activity across a set of genes in the tumor rather than counting chromosomes. The best validated example is the 15-gene DecisionDx-UM test, which sorts tumors into Class 1 (low risk of spreading, further divided into 1A and 1B) or Class 2 (high risk of spreading). Multiple studies, including prospective, multi-year follow-up research, have supported its ability to predict which patients are more likely to develop metastasis (cancer spread) within about five years. A separate minority of uveal melanoma is linked to an inherited condition called BAP1 tumor predisposition syndrome, which is a different topic from the tumor testing described here since it involves a gene change present throughout the body, not only in the tumor; your doctor or a genetic counselor can tell you whether this kind of testing applies to your situation.

None of these results change the diagnosis itself. What they change is the surveillance plan: someone with a low risk (Class 1) result may need less frequent liver imaging, while someone with a high risk (Class 2) result or monosomy 3 may be monitored more intensively and may be a candidate for clinical trials of additional treatment. Talk with your doctor about whether this testing is right for you and what you would do differently with the results before you have it done.

Liver Imaging and Liver Function Tests

Because uveal melanoma spreads through the bloodstream rather than through the lymph system, and has a strong tendency to travel to the liver specifically, doctors typically check the liver at the time of diagnosis, before treatment begins, to look for any sign that the cancer has already spread. This usually includes an ultrasound of the abdomen, and sometimes an MRI or CT scan of the liver for a more detailed look. A blood test called liver function tests checks for higher than normal levels of certain substances that the liver releases, which can be an early clue that something needs a closer look, though normal results do not completely rule out spread.

This liver-focused approach is one of the more unusual features of uveal melanoma care compared with many other cancers, and it continues for the long term after treatment as well, since spread to the liver can appear years after the original tumor was successfully treated. Ongoing liver surveillance is described in more detail in our guide on eye cancer staging.

Chest Imaging

A chest x-ray or, less commonly, a CT scan of the chest may also be done at diagnosis to check the lungs, since the lungs are another possible, though much less common, site of spread. This is a standard part of a complete staging workup rather than a sign that anything abnormal is expected.

Retinoblastoma Is Diagnosed Differently

Retinoblastoma is a different eye cancer that mainly affects young children, usually before age 5, and it is diagnosed differently than uveal melanoma in adults. If you are reading this section because of a diagnosis in your child, know that this cancer is generally very treatable, especially when caught early, and the frightening feelings you may have right now are completely normal.

Because young children cannot hold still for a detailed eye exam, doctors typically perform an examination under anesthesia, meaning your child is given medication to sleep briefly while the ophthalmologist carefully examines both eyes with the pupils dilated. During this exam, doctors often use a specialized wide-field camera system, commonly known by the brand name RetCam, to take detailed photographs of the retina that document the size, number, and location of tumors and allow accurate tracking over time. Ultrasound of the eye may also be used to measure tumor thickness, similar to how it is used in adults.

MRI of the eye sockets (orbits) and brain is generally preferred over CT scanning in children with retinoblastoma. This is worth explaining, because it surprises many parents: children with the inherited form of retinoblastoma carry a change in the RB1 gene in every cell of their body, which also raises their lifetime risk of certain other cancers, and exposing them to the radiation used in CT scans could add to that risk. MRI provides detailed images using magnets and radio waves instead of radiation, so it is used preferentially, especially to look for tumor spread toward the optic nerve or brain.

Retinoblastoma can usually be diagnosed without a biopsy at all, based on the child's eye exam and imaging findings alone. What is essential for retinoblastoma, and different from adult uveal melanoma, is genetic testing. An RB1 gene test on a blood or tissue sample can tell whether a child has the heritable form (which can run in families and is more often found in both eyes) or the nonheritable form (usually a chance event affecting one eye only). Genetic counseling is strongly recommended for the whole family, since this result affects screening recommendations for siblings and future children, not just the child who has been diagnosed. Our guide on eye cancer risk factors has more on how genetics differs between retinoblastoma and uveal melanoma.

Source: National Cancer Institute

What About a Pigmented Spot Found by Accident?

If you are reading this guide because your eye doctor just told you they found a pigmented spot during a routine dilated exam, the most likely explanation, by far, is a choroidal nevus. A nevus is a benign (not cancerous) collection of pigment-producing cells, essentially a freckle inside the eye, sitting in the choroid layer behind the retina. Choroidal nevi are common; many adults have one without ever knowing it, since they usually cause no symptoms and do not affect vision.

The overwhelming majority of these spots stay exactly as they are for a lifetime and never need treatment. Your doctor is watching for a small number of specific features that raise the level of concern and suggest closer monitoring or, occasionally, treatment. These include orange pigment visible on the surface of the lesion, fluid collecting underneath the retina near it (subretinal fluid), a thickness greater than about 2 millimeters, and a particular pattern on ultrasound called low internal reflectivity. None of these features alone means cancer is present, but together they help your doctor decide how closely to watch a spot.

Growth over time is one of the most telling signs, which is exactly why fundus photography and ultrasound measurements matter so much for monitoring. In one large study following more than 2,500 patients with choroidal nevi over many years, the rate of a nevus progressing to become a melanoma was reported at about 8.6 percent by 5 years, 12.8 percent by 10 years, and 17.3 percent by 15 years, meaning the great majority of nevi remained stable throughout the follow-up period. Typical monitoring for a nevus without high-risk features involves a dilated eye exam with repeat photographs roughly every six to twelve months, sometimes with periodic ultrasound, so any change can be caught early. If your doctor recommends more frequent monitoring, it is because a specific feature caught their attention, not because they expect the worst.

What Happens After Your Test Results Come Back?

Once your exam, imaging, and any genetic testing are complete, your doctor uses that information to determine the stage of the cancer, meaning how large the tumor is and whether it has spread. Staging for uveal melanoma considers the tumor's size, its exact location within the eye (iris, ciliary body, or choroid), and whether there is any spread beyond the eye. You can read a full explanation in our guide to eye cancer stages.

Because uveal melanoma is rare, care is usually best coordinated by a multidisciplinary team built around an ocular oncologist, sometimes alongside a radiation oncologist, medical oncologist, and ophthalmic pathologist. Being seen at a specialized ocular oncology center, even if it means traveling for an appointment or two, gives you access to doctors who see this specific cancer regularly rather than only occasionally. It is entirely reasonable, and encouraged, to seek a second opinion, particularly before deciding on a treatment plan that could affect your vision or your eye.

Your genetic test results, if you had them, become part of planning your surveillance schedule going forward. A lower risk result generally supports a somewhat less intensive monitoring schedule, while a higher risk result, or a finding of monosomy 3, typically leads to closer, more frequent liver imaging and blood testing, and may open the door to clinical trial options. You can read more about weighing treatment choices in our eye cancer treatment guide, explore ongoing clinical trials, and see our list of questions to ask your care team to help you prepare for your next appointment.

Every person's situation is different, and this guide cannot replace a conversation with your own doctor. Please talk with your care team about what your specific test results mean and what they recommend for you.