What is it?
Iris melanoma is a malignant tumour or the iris.
Pigmented iris lesions
The iris is the coloured part of the eye that surrounds the pupil. In most people the iris is a uniform blue or brown colour.
In some individuals clumps of pigment cells are present on the surface of the iris. Known as iris naevi, these “freckles” develop early in life and are quite normal in their behaviour. They almost never cause problems.
In very rare circumstanses iris naevi can change into malignant melanomas and it is also possible for melanomas to arise spontaneously.
Iris melanomas are cancers that slowly grow and will eventually threaten the eye and vision if not removed. In approximately one in ten patients the tumour will spread to other parts of the body and can cause death.
How is it diagnosed?
Iris naevi and melanomas are very small. They may be noted by the patient or friends but most are discovered during routine examination by an optometrist.
When a naevis or melanoma is discovered patients are referred to an ophthalmologist for futher examination.
Is it a melanoma?
Ophthalmologists examine the eye with a slit lamp microscope looking for the presence or absence of a number of features known to be more common in melanomas than naevi.
Changes that suggest a pigment spot is likely to be a melanoma include:
- Documented growth
- Larger size and greater thickness
- Variation in pigmentation
- Distortion of the iris or pupil margin
- Abnormal blood vessels
- Spread into surrounding parts of the eye
There are no drug or laser treatments for iris melanoma.
Radiation can be used to treat very large tumours when:
- Surgery is unlikely to preserve vision
- Life expectancy is short
In almost all cases the only treatment for a suspected iris melanoma is surgical removal. Occasionally it is appropriate to observe carefully.
The surgical process
The path to surgery and beyond involves several steps:
- The decision to operate
- The surgery itself
The decision to operate
The decision to operate is only made after consideration of many factors that include:
- Certainty of diagnosis
- The presence of other eye disease
- Health and age of the patient
- Patient wishes
Certainty of diagnosis
Naevi and melanomas are almost always diagnosed clinically, as opposed to diagnosis by a specific test. Sometimes it is difficult to be sure if an iris lesion is a melanoma. When surgery is contemplated a second opinion by another ophthalmologist is usually obtained.
Other eye disease
The decision whether to operate, and which operation to perform, may be modified by the presence of other eye disease. For example a suspicious lesion may be observed for longer if the eye involved has much better vision than the fellow eye.
Patient health and age
The critical decision is always “what is best for each patient”. Iris melanomas can spread throughout the eye and body, but are generally a slow growing tumour. Thus a patient’s general health and age may influence decision making.
In general, younger patients are more likely to need surgery due to the greater risk of the tumour slowly damaging their vision or affecting their life expectancy. Older and unwell patients may decide they are prepared to take the risk the tumour will not cause problems in their lifetime.
Prior to surgery patients undergo a medical examination to make sure they are fit for surgery and to ensure, as much as possible, that there has been no tumour spread.
Surgery for iris melanoma is a major undertaking. Some patients decline surgery after considering the stress and risks involved.
The surgery itself
The type of surgery depends on how large the tumour is and its location. There are two main operations:
Depending on where and how much tissue is removed, surgery may involve suturing of the iris to reconstruct the iris and pupil.
An iris melanoma treated by iridectomy. See preoperative photo above.
When the tumour is small it is usually possible to remove just a small piece of the iris, a procedure known as iridectomy.
An iridectomy is usually performed under general anaesthesia and takes approximately an hour.
Larger tumours may have spread backwards beneath the white of the eye and into an adjacent eye structure called the ciliary body. This requires a more extensive operation known as iridocyclectomy.
Surgery is usually performed under general anaesthesia and takes about two hours.
The process of surgery
Patients requiring iridectomy and iridocyclectomy are usually admitted to hospital overnight to ensure good postoperative pain and nausea control.
The removed piece of tissue is sent to a laboratory for review by a pathologist who specialises in eye disease. It usually takes a week to ten days to analyse the tissue.
Risks of surgery
There are many potential complications of iris surgery. In addition to the normal risks (infection, bleeding etc) the specific risks of iris surgery include:
- Abnormal appearance of the iris and eye
- Blurred or distorted vision
- Glare and halos
- Double vision
- Inadequate excision. All tumour surgery balances the need to remove the abnormal tissue while preserving normal tissue. It can be very difficult to define the exact borders of a tumour and occasionally the pathologist reports that it is not certain that all tumour is removed.
- Unnecessary surgery. A very important potential complication, which occurs in approximately 5% of cases is the unexpected diagnosis that the suspected melanoma was in fact a naevus.
- Eye pressure abnormalities
- Retinal detachment
- Spread of tumour cells, either undetected at time of surgery or as a result of surgery
FAQs and Links
If the spot has been there all my life, why does it need removal?
Naevi that have been present for many years can turn malignant and need removal.
How do we know it’s definitely a melanoma?
The diagnosis is made by observing a number of features known to be more common in melanoma than naevi. Unfortunately it is impossible to be sure until the lesion is examined by a pathologist.
Can a biopsy be done before surgery is performed?
In rare cases a biopsy is undertaken. Usually the diagnosis is so certain that biopsy would not give additional information. A biopsy can also miss tumour cells.
Will surgery affect my vision?
In most cases vision will be affected, but usually only to a minor degree.
Will I die from melanoma?
It is uncommon for melanoma to spread but the risk is very real.