The Lacrimal Drainage System

Definition

The tear drainage system of the eye consists of the lacrimal puncta, canaliculi, lacrimal sac, and nasolacrimal duct. It serves to transport tears from the eye and conjunctival sac to the nose. The eyelids also form an important component of this system by serving as a physiological pump, propelling tears to the medial canthus.

Key Features

The orbicularis muscle and eyelids act as a lacrimal pump for tear drainage.
The drainage system is composed of the puncta, canaliculi, lacrimal sac, and lacrimal duct.
Eyelid malposition or malfunction can result in epiphora by not moving tears into the lacrimal drainage system.
Stenosis or occlusion anyplace along the drainage conduit results in epiphora and possible infection.
Careful clinical testing can help localize the site of obstruction.

Associated Features

Congenital obstruction is usually caused by an imperforate membrane at the nasal end of the lacrimal duct (valve of Hasner).
Acquired obstruction may result from chronic fibrosis of the duct, trauma, or previous nasal or sinus surgery.
Correction of congenital obstruction is typically achieved with a simple probing procedure.
For acquired obstructions, a dacryocystorhinostomy is usually required for permanent resolution.
Eyelid position, laxity, and malfunction must be assessed.

Introduction

Under normal circumstances the tears secreted should equal those eliminated so that neither a dry eye nor symptoms of a watery eye occur. Tearing (a watery eye) may be caused by hypersecretion of tears or decreased elimination, called epiphora ( Table 12.12.1 ). Hypersecretion may result from an increased production of tears from stimulation of the neurophysiological pathway either centrally or as a local reflex. Decreased elimination is caused by reduced passage of tears into or through the lacrimal drainage system, as a result of eyelid malfunction or malposition, or outflow stenosis/obstruction. The cause of the tearing can be estimated by the clinical symptoms and confirmed by clinical signs and tests.

Table 12.12.1

Causes of Tearing

Lacrimation (Hypersecretion)	Epiphora (Decreased Tear Elimination)
Lacrimation (Hypersecretion)	Anatomical Factors	Physiological Dysfunction
Anterior blepharitis and meibomian gland dysfunction Corneal foreign bodies Corneal irritation with dry spots Ocular surface inflammation Refractive errors Thyroid dysfunction	Punctal, canalicular, or nasolacrimal duct strictures or obstructions Foreign bodies (e.g., lacrimal stones) Extrinsic or intrinsic tumors	Orbicularis muscle weakness Punctal or eyelid malpositions Nasal obstruction with normal lacrimal pathway

Anatomy and Physiology

Tears are secreted by the lacrimal gland, with a 24-hour secretory volume of approximately 10 mL. With blinking, the palpebral aperture closes from lateral to medial, and tears are pumped along the marginal tear strips of the upper and lower lids toward the lacrimal lake at the inner canthus. In the normal resting state, most tears are lost by evaporation, and only a small volume passes down through the nasolacrimal passageways.

Tears pass from the lacrimal lake into the canaliculi through the puncta mainly by capillarity. It is important that the puncta of each lid contact the opposite lid on closure and thereby become physiologically occluded. When the lids separate, capillarity draws the tears into the empty canaliculi. Tears then flow to the common canaliculus and lacrimal sac because of a combination of factors :

A change in the caliber of these passages
A change in pressure within the canalicular passages
A pumping function (lacrimal pump) of the orbicularis muscle that surrounds these passages

Tears flow into the inferior meatus of the nose through the effect of the lacrimal pump, gravity, and to a lesser extent, pressure changes within the nose as a result of respiration. Valves within the drainage system permit only one-way flow of tears.

Evaluation of Epiphora

Clinical History

The history of symptoms associated with tearing is important. Outflow obstruction is typically worse in the morning, when outside, or in the cold. The tears usually drain down medially along the tear trough.

Pain at the side of the nose suggests dacryocystitis, but pain in the eye may be caused by foreign bodies, keratitis, recurrent corneal erosion, iritis, or glaucoma. Itchiness suggests an allergic problem rather than lacrimal obstruction. Grittiness and burning of the eyes associated with tearing suggest a lid margin and tear film problem, such as occurs in blepharitis and meibomian gland dysfunction, keratitis sicca, or dysthyroid eye disease.

A history of topical medication such as echothiophate iodide (phospholine iodide), epinephrine (Adrenalin), or pilocarpine drops is important, because they may produce lacrimal obstruction. Chemotherapy such as 5-fluorouracil and radiotherapy can cause obstruction in the canaliculi. Photodynamic therapy also has been associated with canalicular stenosis.

Physical Examination

Eyelids

Poor orbicularis muscle tone and reduced lacrimal pump dysfunction may be presumed if the lid can be pulled more than 8 mm away from the globe, if there is decreased snap-back, or if there is frank ectropion or floppy eyelid syndrome. The puncta should normally be directed backward into the lacrimal lake to catch the tears. Lesions of the caruncle, such as megacaruncle, may interfere with tear drainage. Blepharitis and meibomian gland dysfunction with dry eyes may cause secondary oversecretion of tears. It is important to detect and correct any eyelid malposition or laxity and treat eyelid margin disease well to reduce watering before embarking on lacrimal surgery.

Lacrimal Passages

Facial asymmetry suggests congenital or traumatic anatomical blockage of the nasolacrimal canal. Any mass at the inner canthus should be palpated to determine whether it is soft (indicating mucus) or firm (suggesting a possible tumor) and whether it is compressible or noncompressible. Orbital signs such as proptosis, displacement of the globe, diplopia, and ptosis could indicate that the lacrimal lesion involves the orbit or vice versa.

Nose

The endoscopic nasal examination is an essential part of every lacrimal evaluation. Nasal and sinus conditions, which range from infections and inflammations to tumors, may result in epiphora. Coexistent sinus disease often causes chronic inflammation and narrowing of the nasolacrimal duct. Symptoms include anosmia (loss of smell), epistaxis, anesthesia around the roof of the nose, and nasal obstruction, which may occur with intranasal tumor.

Clinical Diagnostic Tests

Tear Tests

Dye Tests

The tear meniscus can be seen elevated with fluorescein 2% instilled into the conjunctival fornix when there is delayed outflow.

The fluorescein dye retention test is a physiological test where more fluorescein-stained tears are visible on the white of the eye after 3–5 minutes when there is outflow narrowing or obstruction. Often the tears overflow medially down the tear trough in outflow obstruction and laterally over the outer cheek when there is an eyelid cause, such as wick syndrome caused by excess upper eyelid overhanging skin.

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