Aim: To identify clinical factors associated with secondary elevated intraocular pressure (IOP) in eyes with iris malignant melanoma
Methods: A retrospective case series of 169 consecutive patients with microscopically confirmed iris malignant melanoma. The main outcome measure was the presence of tumour induced secondary elevated IOP. Cox proportional regression models were used to calculate the relation of clinical features to elevated IOP.
Results: Of 169 patients with microscopically proved iris melanoma, 50 (30%) presented with tumour induced secondary elevated IOP. The mean pressure in those eyes with elevated IOP at diagnosis was 33 mm Hg (median 31 mm Hg, range 23-65 mm Hg). The tumour configuration was nodular in 23 (46%) and diffuse in 27 (54%) with a mean base dimension of 7.4 mm and thickness of 2.0 mm. Invasion of the angle structures by melanoma seeds was visible for a mean of 7 clock hours (median 7, range 0-12 clock hours). The mechanism of elevated IOP was judged to be outflow obstruction from tumour invasion into the trabecular meshwork. There were no cases of neovascular glaucoma. The tumour was ultimately managed with enucleation in 30 patients (60%), local resection (iridectomy, iridocyclectomy, or iridocyclogoniectomy) in 11 (22%), and plaque radiotherapy in five (10%). In four cases (8%), observation of cytologically low grade tumour was the patient's preference. Using multivariate analysis, the clinical factors at initial evaluation associated with tumour induced secondary elevated IOP from iris melanoma included increasing extent of tumour seeding in the anterior chamber angle (p=0.01) and poor visual acuity at presentation (p=0.02).
Conclusions: Microscopically confirmed iris melanoma demonstrates tumour related elevated IOP in 30% cases at the time of presentation, usually secondary to tumour involvement of the trabecular meshwork obstructing aqueous outflow. Enucleation is necessary in the majority of these patients (60%) as opposed to those cases without elevated intraocular pressure (18%).