Variation in intraocular pressure (IOP) from preoperative measurement throughout brachytherapy and postoperative measurements. Error bars indicate standard errors of the means.
Bhatia SK, Covert DJ, Wirostko WJ. Intraocular Pressure Elevation During Radioactive Plaque Brachytherapy for Uveal Melanoma. Arch Ophthalmol. 2011;129(5):664-676. doi:10.1001/archophthalmol.2011.94
Uveal melanoma is the most common primary intraocular malignant neoplasm in adults, with an average incidence of 6 cases per 1 million people per year.1 The Collaborative Ocular Melanoma Study has shown that radioactive iodine 125 plaque brachytherapy offers equivalent survival compared with enucleation.2 While allowing preservation of the eye, brachytherapy has many potential complications, including dry eye, cataract, radiation retinopathy and optic neuropathy, glaucoma, and vision loss.3 To our knowledge, intraocular pressure (IOP) fluctuation during brachytherapy has not been previously described. The purpose of this investigation was to quantify the IOP changes during brachytherapy. Based on clinical experience, we speculated that the IOP would increase during brachytherapy and that older age, presence of glaucoma or diabetes mellitus (DM), larger radiation doses, larger tumor size, lack of rectus muscle disinsertion, and anterior tumor location may be associated with larger IOP elevations.
This was a retrospective record review of all patients undergoing Collaborative Ocular Melanoma Study–style brachytherapy at the Eye Institute of the Medical College of Wisconsin between January 1, 1996, and December 31, 2007. Institutional review board approval was obtained. Patients were identified by billing record search. Exclusion criteria included being younger than 18 years, having nonmelanotic tumors, and having incomplete medical documentation. The following data were gathered: preoperative IOP, age, sex, history of DM or glaucoma, tumor location and height, radiation dose, plaque diameter, daily IOP during brachytherapy, muscle disinsertion, and use of topical antiglaucoma medications.
Of 113 patients identified as having uveal melanoma, 40 were excluded owing to incomplete records. There were 33 men and 40 women. The mean (SD) age was 61.9 (15.7) years. One patient had open-angle glaucoma, no patients had ocular hypertension, and 12 patients had DM.
Three IOP variables were constructed: a preoperative IOP composite for each patient, defined as the average of preoperative IOP measurements (≤3 measurements); delta IOP (ΔIOP), or the change in IOP as measured on a perioperative day minus the preoperative composite; and the maximum ΔIOP (ΔIOPmax) for each patient.
The mean preoperative IOP composite was 16.0 mm Hg. This was statistically different from the mean IOPmax of 24.3 mm Hg during brachytherapy (P < .001) but not statistically different from the mean IOP of 15.5 mm Hg 1 day after plaque removal (P = .24) (Figure). The mean (SD) ΔIOPmax during plaque therapy was 8.5 (6.0) mm Hg. This was not statistically different for tumors at the posterior pole, midperiphery, and ciliary body (P = .15). Using a linear regression model, there was no relationship between tumor height and ΔIOPmax (P = .53) or between the mean total radiation dose and ΔIOPmax (P = .46). There was limited correlation between plaque diameter and ΔIOPmax using a linear regression model (r2 = 0.07; P = .02). The ΔIOPmax for patients with DM was not statistically different from the ΔIOPmax for those without DM (P = .40). Eighteen patients with extraocular muscle disinsertion did not have statistically different ΔIOPmax compared with 55 patients without extraocular muscle disinsertion (P = .72).
This study demonstrated a statistically significant trend of increased IOP of 8 mm Hg in eyes treated with Collaborative Ocular Melanoma Study–style iodine 125 brachytherapy that persisted while the plaque was in place but resolved by the first postoperative day. Ten patients (14%) experienced IOP increases of 15 mm Hg or more, and 23 (32%) required topical hypotensive therapy. These medications may minimize the IOP elevation associated with brachytherapy. Factors such as age, DM, plaque size or location, tumor height, and radiation dose do not serve as reliable indicators of who will experience these marked elevations in IOP. Given the number experiencing moderate IOP elevation and our inability to identify these patients preoperatively, regular IOP monitoring may be advisable for patients while undergoing iodine 125 brachytherapy.
Correspondence: Dr Wirostko, Retina Service of the Eye Institute, Medical College of Wisconsin, 925 N 87th St, Milwaukee, WI 53226 (firstname.lastname@example.org).
Financial Disclosure: None reported.
Funding/Support: This research was supported in part by the Heed Ophthalmic Foundation, Cleveland, Ohio, and by an unrestricted grant from Research to Prevent Blindness, New York, New York.