A mole in the eye: the conjunctival naevus on the white of the eye, iris freckles, and when to have a change checked

A mole in the eye is most often a conjunctival naevus (conjunctival nevus in American spelling), a small, flat, brown freckle-like spot on the conjunctiva, the thin clear skin over the white of the eye. It is usually harmless and usually present for years. What matters is whether it is changing, because a change in an adult is the one thing that moves it out of the "leave it alone" group. This page is for the adult who has noticed a spot on the eye and is asking what it is.

What is a mole in the eye, and is it usually harmless?

Usually harmless, yes. The American Academy of Ophthalmology (AAO) calls a nevus a common coloured growth on or in the eye, made of melanocytes, the cells that produce pigment, and likens it to a mole on the skin. A conjunctival nevus is the very common type on the white of the eye, and the AAO says it is usually not cancerous.

The AAO's EyeNet review adds that nevi make up more than 50 per cent of conjunctival lesions and are the most benign of the pigmented ones. They typically appear in childhood and stay stable, though they may darken with puberty or pregnancy. EyeWiki, the AAO's clinical wiki, puts the overall risk of change to melanoma at 1 per cent. Melanoma is the serious pigment-cell cancer, and it is why a surgeon watches these spots at all rather than ignoring them.

Under a slit lamp, the microscope with a light that an eye doctor uses to look at the front of the eye, a nevus is usually well defined and often shows tiny clear cysts inside the pigment. In a series of 410 consecutive patients by Shields and colleagues, cysts were seen in 70 per cent of compound nevi and 58 per cent of subepithelial nevi. A nevus can also be pink or have almost no colour, which surprises people who expect a mole to be dark.

Is a spot on the white of the eye the same as a freckle on the coloured part?

No. They are different lesions in different tissues, though both are called "eye freckles" in everyday speech. The conjunctival nevus sits on the white of the eye. An iris freckle sits on the iris, the coloured ring around the pupil.

The AAO describes iris freckles as tiny dark brown flecks on the surface of the iris, caused by a build-up of melanin, and says they are harmless and usually do not develop into melanoma. The EyeNet iris review calls them flat surface pigmentation, often multiple and in both eyes, and notes they are linked to ultraviolet exposure. An iris nevus is larger, around 3 mm, and grows down into the iris stroma, the thicker layer beneath the surface. It is usually benign too, but it is watched more closely: that review lists distortion of the pupil and a turned-out edge of the iris pigment (iris ectropion) as features of concern.

Where a conjunctival nevus sits is a clue as well. EyeWiki says it is typically found on the exposed part of the white of the eye near the limbus, the edge of the cornea, and rarely involves the cornea itself. A pigmented lesion on the inner surface of the lid, in the fleshy corner by the nose, or on the cornea should raise more concern.

Which changes mean a mole in the eye should be checked this week?

Growth, a change of colour, new blood vessels feeding it, bleeding, a raised or thickened surface, a spot in an unusual place, or a new mole appearing in an adult. Do not wait for the next routine visit with any of these. Book a check within the week.

The sources agree on the pattern. EyeWiki says a nevus can change colour and size in adolescence, but that change in an adult should raise suspicion of malignancy. Its red flags are a raised, nodular look instead of a flat one, change in colour or size in an adult, an unusual location and involvement of the cornea. The EyeNet review lists increased vascularity, enlargement and colour change as reasons for prompt evaluation. The AAO adds that a pigmented spot developing later in life may carry a greater risk than one present from birth.

Two reassurances belong beside that list. First, change is not the same as cancer. EyeWiki points out that hormonal changes, inflammation and the growth of cysts commonly explain a nevus that looks different. Second, the long-term numbers are calm. In the 149 patients Shields followed for a mean of 11 years, lesion size was stable in 92 per cent and colour in 87 per cent. Three patients in the whole series of 410 developed melanoma, over a mean of 7 years. Calm numbers are still no reason to guess from a mirror. A photograph and an examination settle it.

What does an examination of a mole in the eye involve?

A slit lamp examination, photographs, and a plan to compare. It is quick and does not hurt. Drops to widen the pupil are used when the surgeon needs to look at the back of the eye.

The EyeNet review advises slit-lamp photography at the first visit as the baseline, then a yearly examination while the lesion stays stable. The AAO says photographs are used to document nevi, with follow-up commonly at six-month intervals at first, and that a nevus which does not change over a year or two is not likely to be a melanoma. For an iris lesion, the EyeNet iris review adds measurements at the slit lamp, sometimes ultrasound imaging of the front of the eye, and a dilated examination of the back of the eye.

The photograph matters more than people expect. Memory cannot compare a spot against last year's size and shade, and a phone selfie varies with the light. A standardised image taken the same way each visit is what allows a surgeon to say "unchanged" and mean it. I would also ask whether a spot is truly pigment. A brown patch can be a nevus, a surface growth such as a pinguecula (see the page on growths on the white of the eye), or a flat, dusting-like pigmentation that deserves a different conversation.

When is a mole in the eye removed, and what does the biopsy decide?

It is removed when it is changing, when the diagnosis is uncertain, or when it irritates the eye or the person cannot live with its appearance. Excision means taking the lesion out with a small margin. The biopsy is the examination of that tissue under a microscope in the laboratory.

The medical case for removal is change. The AAO says most nevi do not need treatment, since they do not affect vision or health, and the EyeNet review recommends excision when a change in colour or size is documented. EyeWiki gives the same instruction for growth or colour change. Irritation and appearance are different reasons. They are legitimate, but they are a personal decision, made after the surgeon explains the risks of any operation on the eye surface and that the removed tissue is sent to the laboratory either way.

What the biopsy decides is the diagnosis. It says whether the tissue is a nevus, whether pigment-cell change has started, or whether it is a melanoma, and the answer sets the next step: reassurance and routine review for a nevus, or further assessment and treatment if it is not. It is also why a pigmented spot on the eye surface is not one to treat with a laser, a cream or a device that destroys it: once it is destroyed there is no tissue left to examine, so when removal is needed it is removed whole and sent to the laboratory. A spot that has been burned away cannot be looked at. If a lesion is removed for cosmetic reasons and turns out to be something else, the opportunity to know has gone.

What about a mole inside the eye, behind the pupil?

That is a choroidal nevus, and it belongs to a general ophthalmologist or a retina specialist, not to an oculoplastic surgeon. The choroid is the layer of blood vessels under the retina. A choroidal nevus cannot be seen from outside, only on a dilated examination of the back of the eye.

The AAO describes it as visible only at an eye exam, grey, yellow, brown or multicoloured, and lists a raised appearance, orange colouring or fluid leakage as warning signs. Most are found by chance at a routine examination, which is a good argument for having one. I explain surface lesions and their removal. For a spot seen inside the eye, the right doctor owns that decision, and I would rather say so than guess.

Sudden flashes, a new shadow in the vision or blurred sight are not features of a surface mole. They need an urgent eye examination of their own, whatever else is on the eye.

Where do a mole on the eyelid and a blue-grey patch fit?

They are separate problems with separate pages. A mole on the lid margin, where the lashes grow, is a skin lesion with its own rules, set out in the page on a mole on the eyelid margin. A blue-grey patch around the eye since birth is usually a different condition altogether, naevus of Ota, which needs an eye doctor for reasons that have nothing to do with a laser, explained in the page on naevus of Ota and eye monitoring.

The common thread is the same. A pigmented spot that is new, changing or in an unusual place deserves a proper look, and the same rule applies on the skin of the lid, covered in the page on eyelid skin cancer warning signs. More on the eye surface sits in the eye surface section, and the overview of what an eyelid and eye problem can mean is in the main guide to tired-looking eyes.

One sentence to keep: a mole in the eye that has not changed in years is usually a freckle, and one that has changed in an adult is a reason to be examined this week, not this year.