Chapter 4

■Canalicular inflammation may lead to loss of compliance and stenosis, with lacrimal symptoms occurring despite anatomical patency.

■Microbial canaliculitis is frequently overlooked, leading to a delay in diagnosis and management.

■Failure adequately to remove canalicular stones and debris is a common cause for persistent canaliculitis.

■Canalicular epithelial inflammation due to primary herpes simplex infection is a common cause of canalicular, or common canalicular, occlusion.

■Subepithelial canalicular inflammation—as seen with lichen planus (LP)—may lead to a more severe and extensive annular fibrosis and carries a poor prognosis.

■Systemic chemotherapeutic agents, including radioiodine, 5-fluorouracil (5-FU), mitomycin C (MMC), and docetaxel, may injure the canalicular epithelium, the evidence suggesting active concentration of these agents by the lacrimal outflow structures.

■The surgical approach to canalicular occlusion depends on the extent of disease.

■Dacryocystorhinostomy (DCR) with retrograde canaliculostomy is the preferred surgery for proximal and midcanalicular occlusion.

■The indication for primary placement of a Jones canalicular bypass tube is the total absence of all distal canalicular and common canalicular structures, with this ascertained during open lacrimal surgery.

■The indication for secondary Jones tube placement is a functional failure after primary DCR with retrograde canaliculostomy.

■A canalicular bypass tube should be sutured such that the tube flange is held clear of the healing carunculectomy site; the function is not to prevent prolapse of the tube. As such, an encirclage suture is required only during primary placement of a bypass tube, when carunculectomy has just been performed.

4.1Introduction

Canaliculitis, either epithelial or pericanalicular inflammation, has many underlying causes with rather characteristic clinical patterns. Although certain etiologies, such as herpetic canaliculitis, are rapidly progressive, others are insidious and frequently pass unrecognized until the onset of lacrimal symptoms. Inflammation, either within the epithelium or deep to its basement membrane, leads to scarring with a reduction of both longitudinal compliance and cross-sectional area of the affected canaliculus; these changes result in impaired function of both the active pumping mechanism and the static drainage (Table 4.1).

This review considers idiopathic, infective, and iatrogenic causes of canalicular inflammation and obstruction, but canalicular trauma—comprehensively reviewed elsewhere—is excluded [24, 27].

4.2Embryology, Anatomy, Physiology, and Pathophysiology of the Canalicular System

The lacrimal drainage pathway arises, at day 32, from a thickening of the ectoderm in the naso-optic fissure. This ectoderm descends into the surrounding mesoderm and forms a cord that extends from the developing eyelids to the nasal space, the cord subsequently forming a lumen by disintegration of the central ectoderm.

The lacrimal puncta, ampullae, and canaliculi form the proximal, high-resistance, elements of the lacrimal drainage system: Measuring 0.3 mm in diameter, the puncta lie within the lacrimal papillae and drain into the

6 mm long in the upper lid and 8 mm in the lower, have an internal diameter of about 0.4 mm, and are surrounded

Table 4.1. Canalicular inflammation: etiology

Infection

1. Chronic staphylococcal lid disease

42. Periocular herpes simplex infection

3. Bacterial and fungal canaliculitis

Systemic inflammatory diseases

1.Lichen planus

2.Ocular cicatricial pemphigoid

3.Drug eruptions (Stevens–Johnson syndrome)

Iatrogenic causes

1.Chemotherapeutic agents

■5-Fluorouracil

■Taxanes: docetaxel (taxotere) and paclitaxel

2.Local radiotherapy

3.Topical treatment

■Preservative related

■Mitomycin C

4.Lacrimal stents and plugs

by the muscle of Duverney–Horner, which is one element of the physiological lacrimal pump. In about 80% of individuals, the upper and lower canaliculi unite to form the common canaliculus, which—with a diameter of about 0.6 mm—runs medially for 2–3 mm before angulating anteriorly to enter the sac. The internal opening of the common canaliculus lies near the midpoint of the sac, at the level of the lower border of the medial canthal tendon, and the anterior angulation of the common canaliculus (about 60°) as it passes through the lateral wall of the sac forms, in part, the physiological “valve” of Rosenmüller; in addition to punctal apposition on lid closure, the valve helps to prevent the retrograde flow of tears [33].

These structures are lined by a stratified squamous epithelium, with a change to pseudostratified, nonciliated columnar epithelium—similar to that found in the upper respiratory system—occurring near the common canaliculus (Fig. 4.1a). The canaliculi form a low-con- ductance conduit, with tear delivery to the lacrimal sac being dependent on the active “compression pump” mechanism of the pretarsal orbicularis oculi. Thus, physiological pump failure, anatomical misalignment, and canalicular stenosis or obstruction may all lead to lacrimal symptoms, examples being facial palsy, ectropion, and herpetic canalicular block, respectively. Depending on the rate of tear clearance, symptoms include a troublesome awareness of wet or moist eyelids, impaired vision due to a raised tear meniscus (Fig. 4.1b), a “wicking” of the tear meniscus onto the skin at the lateral canthus (Fig. 4.1c), and frank epiphora, with this frequently associated with a secondary eczema of the eyelids.

The relative contribution of the upper and lower canaliculi to tear drainage varies between individuals, and most reports suggest that a single canaliculus is adequate for basal tear drainage [18] but will not cope with drainage during reflex lacrimation.

Summary for the Clinician

■In about 80% of individuals, the upper and lower canaliculi unite to form the common canaliculus.

■Physiologic pump failure, anatomic misalignment, and canalicular stenosis or obstruction may all lead to lacrimal symptoms.

■Most reports suggest that a single canaliculus is adequate for basal tear drainage.