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.

• Nature - tumour arising from melanocytes within the choroid. There are 3 subtypes of tumour, one of which (epithelioid type) is particularly aggressive.
• Epidemiology - most common primary intraocular tumour in adults 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). Incidental finding or tumour may be so advanced as to affect visual acuity or cause a visual field defect. 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.
• 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.
• 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.

• 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
• 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.
• Prognosis - these are harmless.

• 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 - thermotherapy and radiotherapy have been used. Lately, photodynamic therapy has also been used with some success.⁴
• 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. ⁵
• Epidemiology - occurs in 2-7% of patients with cancer. Breast (women) and lung (both sexes) cancers are particular culprits. Other recognised cancers include those of the gastrointestinal tract, the kidney, the skin and leukaemia.
• Presentation - may be asymptomatic, decreased visual acuity and occasionally, diplopia, photophobia, blepharitis, pain, secondary glaucoma, exophthalmos and a detached retina
• Investigations - ultrasound scan, fluorescein angiography, biopsy and systemic investigations (blood tests and imaging)
• Treatment ⁵ - observation (if the patient is asymptomatic and already on systemic treatment) and any of the treatments outlined above for choroidal melanoma (including enucleation for the painful, blind eye) depending on the nature of the lesions
• 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.