Iris melanoma is a rare tumor in clinical practice and its development is primarily associated with increased exposure to ultraviolet radiation. The clinical presentation, apart from unilateral heterochromia, may be asymptomatic, but the unilateral development of glaucomas, as well as cataracts, have been described in the literature. The diagnosis rests on a detailed ophthalmological workup.
Iris melanoma, despite being a very rare occurrence, is the most common malignant disease of the iris  . Although the exact pathogenesis remains unknown, ultraviolet radiation is by far the most important risk factor which may explain (at least in part) why countries like New Zealand (due to the profoundly higher exposure to UV-B light) report higher incidence rates of this tumor  . Solid evidence, however, is yet to be discovered. Conflicting reports exist when it comes to the age of presentation - some authors claim that iris melanoma is most frequently encountered in the first few decades of life , whereas others have documented a mean age of approximately 50 years . Manifestations of iris melanoma are primarily of visual nature  . Most patients present with a pigmented (yellow, brown, or tan-colored) spot on the iris that is often noticed incidentally, and such findings are typical for circumscribed iris melanoma, the most common form  . Unilateral heterochromia of the eye is the characteristic symptom of diffuse iris melanoma     . In up to 30% of patients, additional symptoms and signs are absent, while some of the principal complaints seen in advanced stages of the disease include blurred vision, glaucoma, corectopia, ectropion, hyphema, and anterior chamber inflammation   .
The asymptomatic nature of an iris melanoma may significantly affect the ability of the physician to make the diagnosis, and up to 30 months might pass before the tumor is detected . Having in mind the known risk of metastatic disease (ranging from 5%-13% according to various reports)  , the importance of a properly obtained patient history and a detailed physical examination must be emphasized. If a new lesion on the iris (or a change in eye color) is reported, physicians must include iris melanoma in the differential diagnosis. Because of the fact that this tumor is most often diagnosed while still being very small (2.7mm in average) , a thorough inspection of both eyes is mandatory in order to recognize the lesion. More advanced methods are necessary, however, and techniques such as slit-lamp examination, ultrasound biomicroscopy, fluorescein angiography, and optical coherence tomography (OCT) are recommended in the workup   . Histology and immunohistochemistry have also been described in the literature as valuable tools for differentiation of malignant diseases of the iris  . A viable sample for testing can be obtained through fine needle aspiration biopsy (FNAB), incision biopsy, or a direct approach through the cornea, which might be favored due to the potential risk of seeding malignant cells during the former two procedures   .