Tumours of the Choroid

This is the pigmented, highly vascular layer of the globe lying between the sclera (on the outside) and the retina (on the inside).¹ It is one of the three components of the uveal tract and is shaped a little like the body of a rounded wine glass. The optic nerve emerges at its base and the other two components of the uveal tract sit anteriorly: the ciliary body lies around the rim and the iris stretches over the opening. It is made up of three layers, each of which can be affected by disease processes. There is the external vessel layer, the capillary layer and the internal sheet-like Bruch's membrane. The main function of the choroid is to nourish the outer layers of the retina but it is also thought to regulate retinal heat, to assist in the control of intra-ocular pressure and the pigment absorbs excess light so avoiding reflection.

This is a large topic - please refer to our record dedicated to choroidal melanoma. A brief overview is provided here.

• Nature - tumour arising from melanocytes within the choroid, usually developing from pre-existing melanocytic naevi. There are 3 subtypes of tumour, one of which (epithelioid type) is particularly aggressive.
• Epidemiology - most common primary intraocular tumour in adults (and the second most common type of primary malignant melanoma in the body) occurring mainly in Caucasians of Northern European descent. Very rare in Asian populations and exceptionally rare in children. No sex predilection (although in the unusual cases were it occurs in younger people, it is slightly more frequent in women).
• Presentation - usually during sixth decade (range 50-80 years old). Individuals with lighter coloured eyes are more at risk, particularly if there is a history of significant sunshine exposure. It may be an incidental finding or the tumour may be so advanced as to affect visual acuity or cause a visual field defect or loss of sight. Some patients may complain of brief balls of light travelling across visual field in dim lighting conditions. Floaters and pain are also reported. In later stages, may present with symptoms consistent with disseminated metastatic disease (e.g. weight loss, marked fatigue, cough, change in bowel or bladder habits).
• Investigations - diagnosis can usually be made on simple examination but an ultrasound scan, fluorescein angiography and MRI scanning all help to confirm this. If the diagnosis is still not certain, a fine needle aspiration biopsy can be performed. A general medical examination (including baseline serum biochemical tests and a chest x-ray) is mandatory as metastatic spread is common.
• Treatment - this depends on the size, progression and location of the tumour and on the health of the patient. Brachytherapy (radioactive material is placed in the near vicinity of the tumour) is often the first treatment of choice but external radiotherapy, local resection, radiosurgery and enucleation may all be considered. More recently, it has been found that there appears to be no survival benefit attributable to pre-enucleation radiation and enucleation alone may be carried out.
• Prognosis - 30-50% of these patients will die within 10 years. Where lung metastases are present, life expectancy is reduced to a year and if the liver is also involved, this drops further to 6 months. Mortality is correlated with certain characteristics of the tumour (e.g. size and location) and the patient's age. Patients with apparently small, 'cured' tumours will need ongoing observation for many years.

• Nature - these are similar to naevi present in other parts of the body and are probably present at birth, growing mainly in childhood and rarely beyond puberty.
• Epidemiology - these are present in about 5% of the general population, most commonly in people with dark features.
• Presentation - these tend to be incidental findings. Very occasionally, they may be associated with a retinal detachment and therefore present with symptoms characteristic of this (floaters, flashes, visual field defect).⁴
• Investigations - if the lesion looks suspicious or is thought to have grown during adulthood, it will be investigated as for a melanoma (see above).
• Treatment - typical naevi are left well alone but suspicious lesions are monitored every 3-6 months initially (later every 9-12 months). Fundus photographs are helpful in monitoring changes. Photodynamic therapy has been shown to be effective where the naevus is associated with a retinal detachment.⁴
• Prognosis - these are mostly harmless although certain types (which comprise only a small proportion of naevi) may be associated with a mild visual loss over many years.⁵

• Nature - rare non-malignant condition that may be circumscribed or diffuse (as is found in patients with Sturge-Weber Syndrome, ipsilateral to the naevus flammeus). They may be stationary or fast growing. They are only problematic in that they may be located near the macula (or grow over it) and they can leak so causing a retinal detachment.
• Presentation - visual impairment: third decade of life (diffuse), fourth to fifth decade (circumscribed).
• Investigations - ultrasound scan, fluorescein angiography.
• Treatment - photodynamic therapy has been used with some success;⁶ thermotherapy and radiotherapy are other treatment options.
• Prognosis - visual acuity drops to <6/12 in about 50% of cases (often to 6/60).

• Nature - 90% of metastatic disease affecting the uveal tract occurs in the choroid on account of its high vascularity.
• Epidemiology - occurs in 2-7% of patients with cancer. Breast and lung cancers are particular culprits. Other recognised cancers include those of the prostate, gastrointestinal tract, the kidney, the skin and leukaemia.
• Presentation - decreased visual acuity (most common presentation) and occasionally, diplopia, photophobia, blepharitis, pain, secondary glaucoma, exophthalmos and a detached retina can occur. It may be an incidental finding.
• Investigations - ultrasound scan, fluorescein angiography, biopsy and systemic investigations (blood tests and imaging).
• Treatment - this may range from observation (if the patient is asymptomatic and already on systemic treatment) to any of the treatments outlined above for choroidal melanoma (including enucleation for the painful, blind eye) depending on the nature of the lesions. Radiotherapy is a commonly used modality which, in many cases, enables patients to maintain useful vision for the remainder of their lives.
• Prognosis - this depends on the underlying cancer.

• Nature - rare, slow-growing benign tumour which progressively calcifies and ossifies. It occurs in both eyes in about 25% of cases with asymmetrical disease progression. Visual impairment occurs as a result of the damage to the retina overlying the lesion.
• Epidemiology - 90% of the patients affected are young women.
• Presentation - gradual visual impairment in the second to third decade of life.
• Investigations - ultrasound scan, fluorescein angiography.
• Treatment - the tumour itself does not need treatment but associated overlying retinal changes may require laser treatment.
• Prognosis - this depends on the site of the lesion: if it lies over the macula, it can be sight threatening.

This deeply pigmented tumour often occurs near the nerve head. It is benign and needs no treatment but very occasionally, it can undergo malignant transformation. The more common problem with these tumours is local growth affecting adjacent tissues through displacement effect. This can produce afferent pupillary defects (30%), subretinal fluid (10%), and an enlarged blind spot (75%). There are few treatment options available in the event of growth but if this is extreme, enucleation may be considered. These lesions will be observed for malignant transformation.