Introduction
Anatomy
The lacrimal drainage system consists of the following structures ( Fig. 2.1 ):
- •
The puncta are located at the posterior edge of the lid margin, at the junction of the lash-bearing lateral five-sixths (pars ciliaris) and the medial non-ciliated one-sixth (pars lacrimalis). Normally they face slightly posteriorly and can be inspected by everting the medial aspect of the lids. Treatment of watering caused by punctal stenosis or malposition is relatively straightforward.
- •
The canaliculi pass vertically from the lid margin for about 2 mm (ampullae). They then turn medially and run horizontally for about 8 mm to reach the lacrimal sac. The superior and inferior canaliculi usually (>90%) unite to form the common canaliculus, which opens into the lateral wall of the lacrimal sac. Uncommonly, each canaliculus opens separately into the sac. A small flap of mucosa (Rosenmüller valve) overhangs the junction of the common canaliculus and the lacrimal sac (the internal punctum) and prevents reflux of tears into the canaliculi. Treatment of canalicular obstruction may be complex.
- •
The lacrimal sac is 10–12 mm long and lies in the lacrimal fossa between the anterior and posterior lacrimal crests. The lacrimal bone and the frontal process of the maxilla separate the lacrimal sac from the middle meatus of the nasal cavity. In a dacryocystorhinostomy (DCR) an anastomosis is created between the sac and the nasal mucosa to bypass an obstruction in the nasolacrimal duct.
- •
The nasolacrimal duct is 12–18 mm long and is the inferior continuation of the lacrimal sac. It descends and angles slightly laterally and posteriorly to open into the inferior nasal meatus, lateral to and below the inferior turbinate. The opening of the duct is partially covered by a mucosal fold (valve of Hasner).
Physiology
Tears secreted by the main and accessory lacrimal glands pass across the ocular surface. A variable amount of the aqueous component of the tear film is lost by evaporation, with the remainder of the tears hypothesized to drain substantially as follows ( Fig. 2.2 ):
- •
Tears flow along the upper and lower marginal strips ( Fig. 2.2A ), pooling in the lacus lacrimalis medial to the lower puncta, then entering the upper and lower canaliculi by a combination of capillarity and suction.
- •
With each blink, the pretarsal orbicularis oculi muscle compresses the ampullae, shortens and compresses the horizontal canaliculi, and closes and moves the puncta medially, resisting reflux. Simultaneously, contraction of the lacrimal part of the orbicularis oculi creates a positive pressure that forces tears down the nasolacrimal duct and into the nose, mediated by helically arranged connective tissue fibres around the lacrimal sac ( Fig. 2.2B ).
- •
When the eyes open, the canaliculi and sac expand, creating negative pressure that draws tears from the canaliculi into the sac ( Fig. 2.2C ).
Causes of a watering eye
Epiphora is the overflow of tears at the eyelid margin; strictly, it is a sign rather than a symptom. There are two mechanisms:
- •
Hypersecretion secondary to anterior segment disease such as dry eye (‘paradoxical watering’) or inflammation. In these cases watering is associated with symptoms of the underlying cause, and treatment is usually medical.
- •
Defective drainage due to a compromised lacrimal drainage system; this may be caused by:
- ○
Malposition (e.g. ectropion) of the lacrimal puncta.
- ○
Obstruction at any point along the drainage system, from the punctal region to the valve of Hasner.
- ○
Lacrimal pump failure, which may occur secondarily to lower lid laxity or weakness of the orbicularis muscle (e.g. facial nerve palsy).
- ○
Evaluation
History
Enquiry should be made about ocular discomfort and redness to aid in excluding hypersecretion. Drainage failure tends to be exacerbated by a cold and windy environment, and to be least evident in a warm dry room; a complaint of the tears overflowing onto the cheek is likely to indicate drainage failure rather than hypersecretion.
External examination
Punctal abnormality is the most common cause of lacrimal drainage failure.
- •
The puncta and eyelids should be examined using a slit lamp. It is critical that examination of the puncta is performed prior to cannulation for diagnostic irrigation, which temporarily dilates the punctal opening and masks stenosis.
- ○
There will often be obvious tear overflow from the medial, or less commonly the lateral, canthal region; this is more likely to indicate defective drainage than an irritative cause.
- ○
Visible mucopurulent discharge is more likely to occur with nasolacrimal duct obstruction than a blockage more proximally.
- ○
Punctal stenosis ( Fig. 2.3A ). This is extremely common, and has been reported as present in up to about half of the general population; over half of patients with evident stenosis are asymptomatic, in many cases due to insufficiency of tear production or increased evaporation.
Fig. 2.3
(A) Marked punctal stenosis; (B) punctal ectropion and stenosis; (C) conjunctivochalasis; (D) punctal obstruction by an eyelash; (E) large caruncle; (F) pouting punctum
- ○
Ectropion, either localised to the punctal region or involving the wider lid, is often associated with secondary stenosis ( Fig. 2.3B ).
- ○
Punctal obstruction, usually partial, by a fold of redundant conjunctiva (conjunctivochalasis – Fig. 2.3C ) is common but underdiagnosed.
- ○
Occasionally an eyelash may lodge in the ampulla ( Fig. 2.3D ).
- ○
A large caruncle may displace the punctum away from the globe ( Fig. 2.3E ).
- ○
In the presence of substantial lid laxity, the puncta may rarely over-ride each other.
- ○
A pouting punctum ( Fig. 2.3F ) is typical of canaliculitis.
- ○
The eyelid skin will often be moderately scaly and erythematous in chronic epiphora.
- ○
- •
The lacrimal sac should be palpated. Punctal reflux of mucopurulent material on compression is indicative of a mucocoele (a dilated mucus-filled sac; US spelling – mucocele) with a patent canalicular system, but with an obstruction either at or distal to the lower end of the lacrimal sac. In acute dacryocystitis palpation is painful and should be avoided. Rarely, palpation of the sac will reveal a stone or tumour.
Fluorescein disappearance test
The marginal tear strip of both eyes should be examined on the slit lamp prior to any manipulation of the eyelids or instillation of topical medication. Many patients with watering do not have obvious overflow of tears but merely show a high meniscus (marginal tear strip) of 0.6 mm or more ( Fig. 2.4 ) versus 0.2–0.4 mm normally. The fluorescein disappearance test is performed by instilling fluorescein 1 or 2% drops into both conjunctival fornices; normally, little or no dye remains after 5–10 minutes. Prolonged retention is indicative of inadequate lacrimal drainage. This should be distinguished from the ‘fluorescein clearance test’ used to assess tear turnover in dry eye, in which retained stain is measured in the meniscus 15 minutes after instillation of 5 µl of fluorescein.
Lacrimal irrigation
Lacrimal irrigation should be performed only after ascertaining punctal patency; if absent or severely stenosed, surgical enlargement of the punctum may be needed before canalicular and nasolacrimal duct patency can be confirmed. It is contraindicated in acute infection.
- •
Local anaesthetic is instilled into the conjunctival sac.
- •
A punctum dilator is used to enlarge the punctal orifice ( Fig. 2.5A ), entering vertically and then tilting the instrument horizontally whilst exerting lateral tension on the lid ( Fig. 2.5B,C ).
Fig. 2.5
(A) Dilatation of the inferior punctum; (B,C) dilatation technique; (D) irrigation
(Courtesy of K Nischal – figs A and D)
- •
A gently curved, blunt-tipped 26- or 27-gauge lacrimal cannula on a 3 ml saline-filled syringe is inserted into the lower punctum and, whilst keeping a gentle stretch laterally on the eyelid, advanced a few millimetres, following the contour of the canaliculus ( Fig. 2.5D ).
- •
A hard stop occurs if the cannula enters the lacrimal sac, coming to a stop at the medial wall of the sac, through which can be felt the rigid lacrimal bone ( Fig. 2.6A ). This excludes complete obstruction of the canalicular system. Gentle saline irrigation is then attempted. If saline passes into the nose and throat, when it will be tasted by the patient, a patent lacrimal system is present, although there may still be stenosis; alternatively, symptoms may be due to subtle lacrimal pump failure. Failure of saline to reach the throat is indicative of total obstruction of the nasolacrimal duct. In this situation, the lacrimal sac will distend slightly during irrigation and there will be reflux, usually through both the upper and lower puncta. The regurgitated material may be clear, mucoid or mucopurulent, depending on the contents of the lacrimal sac.
Fig. 2.6
Possible results of probing. (A) Hard stop; (B) soft stop
- •
A soft stop is experienced if the cannula stops at or proximal to the junction of the common canaliculus and the lacrimal sac. The sac is thus not entered – a spongy feeling is experienced as the cannula presses the soft tissue of the common canaliculus and the lateral wall against the medial wall of the sac and the lacrimal bone behind it ( Fig. 2.6B ). As a crimped canaliculus with occlusion of the cannula tip against the canalicular wall can also give this impression, it is worthwhile slightly retracting the tip, increasing the lateral tension on the lid, and gently repeating the attempt to advance the probe. In the case of lower canalicular obstruction, a soft stop will be associated with reflux of saline through the lower punctum. Reflux through the upper punctum indicates patency of both upper and lower canaliculi, but obstruction of the common canaliculus.
Jones dye testing
Dye testing is indicated only in patients with suspected partial obstruction of the drainage system. Epiphora is present, but there is no punctal abnormality and the patient tastes saline in his or her throat on irrigation.
- •
The primary test ( Fig. 2.7A ) differentiates partial obstruction of the lacrimal passages and lacrimal pump failure from primary hypersecretion of tears. A drop of 2% fluorescein is instilled into the conjunctival sac of one eye only. After about 5 minutes, a cotton-tipped bud moistened in local anaesthetic is inserted under the inferior turbinate at the nasolacrimal duct opening. The results are interpreted as follows:
- ○
Positive: fluorescein recovered from the nose indicates patency of the drainage system. Watering is due to primary hypersecretion and no further tests are necessary.
- ○
Negative: no dye recovered from the nose indicates a partial obstruction (site unknown) or failure of the lacrimal pump mechanism. In this situation the secondary dye test is performed immediately. There is a high false-negative rate – that is, dye is commonly not recovered even in the presence of a functionally patent drainage system. Modifications involving direct observation of the oropharynx using cobalt blue light for up to an hour may reduce the false-negative rate almost to zero.
- ○
