CASE PRESENTATION
On presentation at our clinic, the patient's eye was
comfortable, her visual acuity was 20/40 OD and 20/30
OS, and her IOP measured 25 mm Hg OD and 14 mm
Hg OS (with average corneal thickness) using the aforementioned
drops. An examination of her right eye
revealed a clear cornea and conjunctiva and a deep,
quiet anterior chamber. A lightly pigmented inferotemporal
iris mass appeared to have internal vascularity and
was associated with ectropion uvea (Figure 1). The surface
of the iris showed lightly scattered pigmentary deposition,
especially near the lesion. There was mild
nuclear sclerosis without focal opacification. The posterior
segment was unremarkable except for nearly total
cupping and excavation of the optic disc. Gonioscopy
showed increased pigmentation of the angle in the
patient's right eye compared with mild pigmentation in
her left eye. The view to the inferotemporal angle was
partially obscured by the mass, but no direct involvement
was discernible. Ultrasound biomicroscopy
(UBM) showed an iris mass that radially measured
3 mm X 1.4 mm, but no ciliary body involvement was
noted (Figure 2). Initial visual field testing of the patient's
right eye (24-2 Swedish interactive threshold
algorithm-standard) showed a nearly total blackout.
The examination of her left eye was unremarkable.
A review of the patient's records revealed that she had initially been seen 5 1/2 years earlier for a raised iris mass (Figure 3), with radial dimensions of 2.5 mm X 1 mm on UBM. At that time, the mass had somewhat distorted the pupil, but the IOP measured in the midteens with no evidence of glaucoma. Gonioscopy had revealed no involvement of the angle. A systemic workup at that time (including computed tomography and bone scans) was negative for any signs of malignancy. Notably, the patient had a medical history of breast cancer, and she had undergone a mastectomy with chemotherapy 12 years earlier, followed by a lumpectomy with chemotherapy and radiation 8 years later for a recurrence. She has been in remission and has been following up regularly with her oncologist for surveillance. At the time of her initial ophthalmic evaluation, the possibility of an iris melanoma was raised, and close observation was advised. The patient, however, was lost to ophthalmic follow-up until recently.
DISCUSSION
This uncommon case of secondary glaucoma from an
iris lesion raises concern about melanoma. The differential
diagnosis of an iris melanoma includes iris nevus,
melanocytoma, iris cyst, and metastasis to the iris.
Although nevi are common, iris melanomas are rare and
account for only about 3% of all uveal melanomas.1
Both nevi and melanomas usually occur in the inferior
half of lightly colored irides among white patients and
can be difficult to tell apart clinically. The presence of
findings such as corectopia, ectropion uveae, internal
vascularity, cataract formation, and even lesion growth
may not be diagnostic. Ophthalmologists, however,
must consider excising lesions that demonstrate growth
as suspected melanoma.2 A careful examination and
documentation of the tumor's size and location using
slit-lamp photography and UBM, if available, are critical
in this regard. Other signs of concern include a large
tumor (> 3 mm in diameter), prominent vascularity,
pigment dispersion or glaucoma, and signs of extension
into adjacent structures.3
Iris melanoma is not very aggressive, and the overall chance of metastasis of a biopsy-proven melanoma is only 5% after 10 years.1 Some risk factors for metastasis are older age, elevated IOP, involvement of the iris insertion and angle, and extraocular extension. Iris melanomas can be circumscribed lesions or diffuse infiltrating tumors that are seen as hyperpigmentation of the iris and/or angle. The standard options for treatment are excision by iridectomy or iridocyclectomy if the tumor is not too extensive, or enucleation if the tumor is not resectable. Plaque radiotherapy is also available as an adjunct or alternative to excision or enucleation in some cases.
Iris melanoma can be associated with elevated IOP in 7% of clinically suspected cases but in up to 30% of microscopically confirmed cases.4 The mechanism by which IOP elevation typically occurs is either direct infiltration of tumor cells into the angle or obstruction of the trabecular meshwork by dispersed pigment (and any engulfing macrophages). Less common mechanisms are angle closure and neovascularization. Treating glaucoma due to iris melanoma can be challenging in light of the contraindication to surgeries such as trabeculectomy, which create a pathway to potential extraocular extension.5 Even laser trabeculoplasty may pose a theoretical risk of promoting the tumor's spread; no evidence supports this concern, however, and a cautious attempt at laser trabeculoplasty away from the areas of tumor involvement may be reasonable if medical therapy fails. Likewise, transscleral cyclophotocoagulation can be performed, preferably in quadrants away from the tumor.
It is worth reiterating the possibility that iris melanoma will present in its diffuse infiltrative form, leading to unilateral glaucoma. If its spread is confined to the angle, creating a rare so-called ring melanoma, it may be mistaken for primary open-angle glaucoma if careful gonioscopy is not performed. Alternatively, if the melanoma also diffusely involves the entire iris, it can be mistaken for a unilateral pigmentary glaucoma and inappropriately treated with surgical filtration.6 A hyperchromic heterochromia of the iris with ipsilateral glaucoma should raise this possibility in the clinician's mind and trigger a careful investigation.
This case was highly suspicious for a primary iris melanoma given the size of the lesion, its documented growth, and the secondary glaucoma induced by the tumor. A metastatic lesion from breast cancer was also a consideration, but it was unlikely, particularly since the systemic workup was normal and typical features of metastatic carcinoma were absent. Because there did not appear to be any direct extension or seeding into the angle, pigment dispersion was the presumed mechanism of glaucoma. The patient began therapy with dorzolamide hydrochloride 2% in addition to her other eye drops, and her IOP decreased to the upper teens, which was acceptable. She was referred to a regional ocular oncologist. Because there was no evidence of extension of the tumor into the ciliary body, the patient did not require enucleation. Rather than undergo extensive iris resection, she elected to receive plaque radiotherapy.
Section Editor Eiyass Albeiruti, MD, is an assistant professor of ophthalmology at the University of Pittsburgh in Pennsylvania. Dr. Albeiruti may be reached at (412) 647- 8199; albeirutie2@upmc.edu.
