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Editor,—Iris cysts may be primary—that is, developmental in nature, or secondary following surgery or penetrating trauma. In the latter case, the condition is due to implantation of epithelial cells from the ocular surface, and thus these lesions are also referred to as epithelial implantation cysts.1 We report the successful treatment of a post-traumatic, recurrent, giant iris cyst by needle aspiration combined with intracyst administration of dilute mitomycin C.
A 32 year old woman was referred with the complaint of decreased vision as a result of a recurrent giant iris cyst in the left eye. She had a vague history of penetrating trauma involving a piece of glass at the age of 8. Laser cystotomy had been performed at other institutions 7 and 4 years before presentation at our hospital; however, recurrence of the cyst occurred soon each time. On our initial examination, the visual acuity was 20/15 right eye and 20/200 left eye. Slit lamp biomicroscopy revealed a full thickness corneal scar and a large iris cyst centred in the inferonasal quadrant, extending over the central visual axis and occupying roughly 60% of the anterior chamber (Fig1A). The anterior surface of the cyst appeared to be in contact with the posterior cornea although the overlying cornea was clear and compact. The intraocular pressure was normal. After pupillary dilatation the cyst was noted to still be blocking the visual axis, with lens opacification in the inferotemporal quadrant observed. The fundus was unremarkable. Ultrasound biomicroscopy (UBM) revealed that the cyst also extended posteriorly to a substantial degree (Fig 1B). Endothelial cell density (ECD) at the central cornea was 2720 cells/mm2 right eye and 1600 cells/mm2 left eye.
Given the history of recurrence following previous attempts at laser treatment of the cyst, a surgical procedure was performed. The cyst was pierced directly using a 30 gauge needle through the peripheral cornea at 1 o'clock. After approximately 0.3 ml of clear fluid was aspirated, the cyst was reduced to roughly one fifth of its original size, and the anterior surface of the cyst was observed to separate from the posterior cornea. Next, 0.3 ml of 10−3 mg/ml mitomycin C (2 mg in 2000 ml of balanced salt solution) was injected into the cyst and left for 5 minutes, after which most of the fluid in the cyst was aspirated. This was followed by injection and aspiration of 0.3 ml of balanced salt solution, repeated three times, in order to wash out any residual mitomycin C. No complications were observed during the procedure. The intraocular pressure (IOP) rose transiently to 22 mm Hg and mild anterior chamber fibrin was noted on the first postoperative day, although these symptoms resolved quickly with topical corticosteroids. At 18 months postoperatively, the visual acuity in the left eye was 20/30, with no recurrence of the cyst by slit lamp or ultrasound biomicroscopy (Fig 2A, B). The IOP was normal and there was no evidence of epithelial downgrowth. At this time, the ECD was 1538 cells/mm2 in the left eye, representing a decrease of only 4%. No other toxicity related to the intracameral use of mitomycin C was detected by clinical examination, electroretinography, colour testing, contrast sensitivity testing, and Humphrey automated perimetry.
Photocoagulation of iris implantation cysts can induce a rise in IOP believed to be due to clogging of the trabecular meshwork by released viscous contents of the cyst.2 Moreover, since the original structure and function of the epithelial lining of the cyst remains fundamentally unchanged, recurrence after photocoagulation is common.2 Total surgical excision may be performed, although the cyst can be adherent to the posterior surface of the cornea and excessive surgical manipulation may induce epithelial downgrowth. Simple transcorneal needle drainage is much less invasive and has the advantage of little cyst fluid entering the anterior chamber; however, it too is associated with recurrence.1
In this case report, we have demonstrated that needle drainage combined with intracyst administration of dilute mitomycin C may be an effective and safe alternative to other treatment modalities. Mitomycin C is a DNA cross linking antineoplastic agent used at doses of 0.2–0.5 mg/ml on exposed Tenon's capsule and sclera in glaucoma filtering surgery, and at somewhat lower doses in surgery for recurrent pterygium, in the attempt to inhibit fibroblast proliferation.3 Toxicity associated with such use can include conjunctival irritation, tearing, and superficial punctate keratopathy. The dose of mitomycin C we used was the same as the dose shown to inhibit proliferation of retinal pigment epithelial cells.4 We speculate that mitomycin C, applied transiently to the lining of the cyst, caused permanent damage to the epithelial and goblet cells which secrete cyst fluid, resulting in regression of the cyst. Although implantation iris cysts represent a relatively rare condition, larger numbers of cases would be necessary to confirm the efficacy and safety of this novel treatment.