Ocular Melanoma: Diagnosis and Staging
Though Ocular Melanoma can be lethal and is fairly difficult to recognize by symptoms alone, periodic retinal examinations by an ophthalmologist have the potential to diagnose a problem at an early stage, therefore saving a patient's life. An examination through a dilated pupil is one of the only ways that a doctor can diagnose ocular melanoma with enough time to save a patient's life.
Though a thorough eye examination by an experienced clinician is the most important procedure for detecting ocular melanoma, ancillary diagnostic testing may also be used. Ancillary diagnostic testing may include fluorescein angiography and ultrasonography.
Fluorescein angiography uses an injection of a fluorescent dye through the hand or arm to allow the photography of the blood vessels in the back of the eye. This procedure is most commonly used to confirm a diagnosis or to create guidelines for a treatment method.
Ultrasonography uses a small probe within the closed eyelid in order to bounce sound waves off of the eyeball. The reflected sound waves produce a 2D image of the interior of the eye, therefore helping a doctor to see abnormal tissues and the blood vessels in the eye.
A CT scan takes a series of detailed pictures of the eye using x-rays and a computer imaging system. These pictures allow doctors to see tumors within the orbits (eye sockets). In some cases, a dye may be injected into a vein so that the tissues are more visible in x-ray images.
An MRI uses a powerful magnet linked to a computer to create images of a targeted area such as the ocular orbits in order to see tumors and irregular tissues.
Ocular coherence tomography (OCT) is an imaging method that uses light beams and a reference mirror to reflect light on the retinal tissue in order to produce cross-sectional images of ocular tissue.
Classification and Staging:
Ocular tumors are typically nodular or dome-shaped. Sometimes, tumors of the eye can be flat with little height. There are four size classifications for ocular tumors:
Small - 1mm-3mm in height; base diameter of at least 5mm
Medium - ~3mm-10mm in height; base diameter less than 16mm
Large - height greater than 10mm; base diameter at least 16mm
Diffuse - a tumor with a horizontal growth pattern; tumor thickness is 20% or less than the greatest base dimension
Because the uveal tract exists without lymphatic channels, ocular tumors spread by local extension or through the blood stream. It is particularly unusual for any sized melanoma of the choroid to invade the optic nerve.