Systemic radioiodine (131I) is used for the management of thyroid carcinoma and has well-documented ocular side effects, including xerophthalmia and chronic conjunctivitis [31]. Symptomatic lacrimal outflow obstruction is less well recognized, occurring in at least 5% of patients, with the distal nasolacrimal duct more commonly affected than the canalicular systems [5]1; whether this effect is mediated by local toxicity from passive flow of 131I into the tears or is due to active uptake by the sodium–iodide symporter (known to exist in both lacrimal and thyroid gland) remains uncertain, although at least one report supported the latter mechanism [4].

Canalicular disease has been reported in 3/14 (21%) patients receiving topical MMC for 2 weeks [16], although another report found punctal stenosis in only 14/100 eyes of 91 patients who received the drop for 1 week (of which only 1 required lacrimal surgery), suggesting that symptomatic canalicular stenosis occurs only rarely and may be related to duration of topical therapy [17]. To reduce canalicular toxicity, some authors advocate temporary punctal occlusion with removable plugs while using MMC drops, which has the additional advantages of increasing drug bioavailability on the ocular surface.

4.5.3 Topical Ophthalmic Treatments

4.5.3.1Preservative-Related Chronic Conjunctivitis

Lacrimal canalicular occlusion may occur after exposure to topical ocular medications, with one study reporting obstruction as little as a month after beginning treatment [21]. Outflow obstruction is most commonly observed 2–5 mm from the lacrimal punctum, with other associated findings including symblepharon, keratinization of the medial canthal tissues, and cicatricial medial entropion.

Canalicular occlusion may follow a chronic inflammatory response to drop preservatives and, if a patient has symptoms of dry eye, features suggestive of chronic allergy (e.g., skin changes, ocular redness or irritation, and a conjunctival papillary response) (Fig. 4.4b) should not be confused with those of aqueous insufficiency.

4.5.3.2Mitomycin C (MMC) Therapy

Topical MMC is proven in the treatment of ocular surface malignancy, such as intraepithelial carcinoma, primary acquired melanosis with atypia, superficial conjunctival malignant melanoma, and sebaceous carcinoma with pagetoid spread. Transient side effects of MMC include an allergic reaction in a third of patients in addition to kerato-conjunctivitis and punctate epithelial keratopathy.

1 A lower dose 131I is used in controlling hyperthyroidism (therapeutic activity 10–15 mCi 131I) compared to managing thyroid carcinoma (30–200 mCi 131I), which in the context of metastatic disease may require substantial cumulative activities (up to 300 mCi 131I).

4.5.4Lacrimal Stents and Plugs

All foreign bodies within the lacrimal outflow tract, including stones, stents, and plugs, incite a mucosal inflammatory response. At about a month after lacrimal surgery, silicone stents typically cause medial canthal irritation and mucus production due to punctal and canalicular inflammatory changes; when stent removal is delayed beyond 3 months, frank exophytic granulomas may occur (Fig. 4.4c, d). Thus, even the most inert of materials is capable of inciting mucosal inflammation, with secondary submucosal fibrosis and risk of canalicular stricture.

Although the vast majority of lacrimal plugs are not used appropriately, a variety of punctal and canalicular plugs are available to treat symptoms of true aqueous insufficiency. Self-degrading collagen plugs are effective for a few weeks, and silicone punctal plugs, which are reasonably well tolerated, are best used to identify those patients in whom permanent outflow occlusion would be appropriate. Other materials include a flexible thermosensitive acrylic material (SmartPlug) that molds to the internal contour of the ampullae, but none is without complication, and all may cause canaliculitis [8, 9, 29, 30]. Intracanalicular plugs have been advocated for the treatment of dry eye for some years, but these tend to migrate into the nasolacrimal sac, be held up at the entrance to the sac (Fig. 4.4e), or become embedded through the common canalicular wall. The presence of a chronic intracanalicular foreign body can fuel a gross conjunctival inflammatory response, and the retrograde discharge of purulent debris further compromises the ocular surface. Indeed, intracanalicular plugs were the cause of lacrimal outflow symptoms in 6% of eyes in one series, with the high prevalence possibly reflecting practice within one particular catchment population [19]; over a quarter of eyes in this study had persistent epiphora after plug removal or reparative lacrimal surgery, presumably due to persistent canalicular stenosis.