Ординатура / Офтальмология / Английские материалы / Oxford American Handbook of Ophthalmology_Tsai, Denniston, Murray_2011

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Lacrimal

Anatomy and physiology 128

The watery eye: assessment 130

The watery eye: treatment 132

Lacrimal system infections 134

128 CHAPTER 5 Lacrimal

Anatomy and physiology

The lacrimal system comprises a secretory component (tear production by the lacrimal gland) and an excretory component (tear drainage by the nasolacrimal system).

Anatomy

Lacrimal gland

This almond-shaped bilobar gland is located in the shallow lacrimal fossa of the superolateral orbit. It is held in place by fascial septa and divided into palpebral (smaller superficial part) and orbital (larger deeper part) lobes by the levator palpebrae superioris aponeurosis. Around 12 ducts run from the orbital lobe through the aponeurosis and palpebral lobe to open into the superolateral fornix.

The gland is of serous type, but also contains mucopolysaccharide granules. It is innervated by the parasympathetic system: superior salivary nucleus (pons) lgreater petrosal nerve lsynapse at pterygopalatine ganglion lzygomatic nerve (V2) llacrimal nerve (V1) llacrimal gland.

Nasolacrimal system

Tear drainage starts with the upper and lower lacrimal puncta (0.3 mm diameter), which are located around 6 mm lateral to the medial canthus. These are angled backward and are located within the slightly elevated lacrimal papilla.

The superior and inferior canaliculi comprise a vertical part (the ampulla: 2 mm long, up to 3 mm wide) and a horizontal part (8 mm long, up to 2 mm wide). The terminal canaliculi usually fuse to form the common canaliculus, on average 2 mm before entering the lacrimal sac. The sac is around 12 mm in length and lies within the lacrimal fossa. The lacrimal fossa lies posterior to the medial canthal tendon and lateral to the ethmoid sinus (although this is variable).

The nasolacrimal duct is around 18 mm long and runs parallel to the nasojugal fold (i.e., inferolaterally). The first 12 mm lies in the bony nasolacrimal canal and the last 6 mm within the mucous membrane of the lateral wall of the nose. It opens into the inferior meatus via the ostium lacrimale just beneath the inferior turbinate.

There are a number of valves along the system, the most important ones being the valves of Rosenmuller (entry into the lacrimal sac) and Hasner (exit from the nasolacrimal duct).

Physiology

Production (secretion) of tears may be basic or reflex.

Basic secretion

•Lid: meibomian glands (number around 60) louter lipid layer, which reduces evaporation.

•Conjunctiva: glands of Krause (number around 28) and glands of Wolfring (number around 3) lmiddle aqueous layer, which has washing and antimicrobial functions; and goblet cells linner mucin layer, which helps stabilize the tear film.

•Lacrimal gland may also contribute to basal secretion.

130 CHAPTER 5 Lacrimal

The watery eye: assessment

This is a common complaint, particularly in the elderly population. It ranges from the transient and trivial (e.g., associated with a local irritant) to the permanent and disabling. Objective quantification is difficult, but the main issue is how much of a problem it is for the patient.

Box 5.1 A systemic approach to assessing the watery eye

Perform nasendoscopy when possible. Consider formal Jones testing and imaging (contrast dacryocystography, lacrimal scintillography) if required. For specific tests, see Chapter 1 (p. 38).

THE WATERY EYE: ASSESSMENT 131

Table 5.1 Causes of the watery eye (common causes in bold)

FB, foreign body; 5-FU, 5-fluorouracil; HSV, herpes simplex virus; KCS, keratoconjunctivitis sicca; OCP, ocular cicatricial pemphigold; TED, thyroid eye disease.

132 CHAPTER 5 Lacrimal

The watery eye: treatment

Increased production

This is usually due to reflex tearing in response to a chronic irritant or disease. Treatment is directed toward controlling the disease process, e.g., ocular lubricants for keratoconjunctivitis sicca (KCS). It is important to explain this to the patient, since it will seem counterintuitive to be treating a watery eye with drops.

Lacrimal pump failure

This is usually a function of lid laxity and ectropion causing punctal eversion. This often leads to secondary punctal stenosis. Treatment is directed toward restoring the position of lid and punctum, often with a lid-shortening procedure (see Table 5.2 and p. 118).

Table 5.2 Surgical procedures to improve nasolacrimal drainage

DCR, dacryocystorhinostomy.

THE WATERY EYE: TREATMENT 133

Decreased drainage

Obstruction may arise at the level of the punctum, the canaliculi, the sac, or the nasolacrimal duct. The extent of surgery required will depend on the level of blockage, but most cases arising distal to the puncta require a dacryocystorhinostomy (Table 5.2).

Dacryocystorhinostomy (DCR)

The aim of a dacryocystorhinostomy is to create an epithelium-lined tract from the lacrimal sac to the nasal mucosa. The conventional external route has a success rate of around 90%.

Endonasal DCR has the advantage of no external scar but is less effective. Laser-assisted endonasal DCR has the lowest success rates, possibly because of the smaller ostium created.

Indication

DCR is used for acquired nasolacrimal duct obstruction or congenital nasolacrimal obstruction in which a probe cannot be passed.

Method

Box 5.2 Outline of external DCR

1.Make cutaneous incision on lateral aspect of nose and inferior to medial canthal tendon (around 8–10 mm long).

2.Dissect down to bone, reflect periosteum from anterior lacrimal crest, and divide the superficial limb of the medial canthal tendon.

3.Reflect the lacrimal sac laterally.

4.Use Kerrison punches to create an opening through the bone of the sac fossa to the nasal cavity.

5.Divide the lacrimal sac and the exposed nasal mucosa vertically to form anterior and posterior flaps.

6.Anastamose mucosa of the sac and the nose by suturing the posterior and then the anterior flaps together.

7.Silastic tubes can be inserted to keep the ostium open if there is concern about premature closure by granulation tissue.

8.Close skin incision.

Postoperative care

If the nose has been packed at the end of the operation, the packing can usually be removed on the first day after surgery. Prophylactic oral antibiotics are commonly prescribed.

Complications

Hemorrhage with epistaxis may occur early (within 24 hours) or late (4–7 days) when clot retraction occurs. Treat with nasal packing (± thrombinsoaked packs). If hemostasis is still not achieved, the vessel may need embolization.

Other complications include failure (closure of the ostium), scar formation, infection, and, very rarely, orbital hemorrhage.

134 CHAPTER 5 Lacrimal

Lacrimal system infections

Canaliculitis

This uncommon chronic condition usually arises from the gram-positive bacteria Actinomyces israelii (streptothrix), but may be due to Nocardia, fungi (Candidia, Aspergillus) or viruses (HSV, VZV).

Clinical features

•Unilateral epiphora, recurrent “nasal” conjunctivitis, inflammation of the punctum and canaliculus, expression of discharge, or concretions from the canaliculi.

•In Actinomyces infection, these are bright yellow concretions (“sulfur granules”). The lacrimal sac is not swollen, and both sac and nasolacrimal duct are patent.

Investigation and treatment

Remove concretions (send for microbiological analysis) and consider irrigation (e.g., with penicillin G 100,000 U/mL or iodine 1%—ensure drainage out through nose, not nasopharynx) and topical antibiotics.

Acute dacryocystitis

This condition is relatively common in patients with complete or partial nasolacrimal duct obstruction. It is usually due to staphylococci or streptococci. Acute dacryocystitis is easily identified and requires urgent treatment to prevent a spreading cellulitis.

Clinical features

•Pain around sac, worsening epiphora.

•Tender, erythematous lump just inferior to medial canthus, may express pus from puncta on palpation, + preseptal cellulitis.

Investigation and treatment

Send discharge to microbiology.

•Antibiotics: systemic (e.g., cephalexin 500 mg 4x/day for 7 days). Consider warm compresses, gentle massage (encourages expression), and incision and drainage if pointing (but may not heal until DCR is performed).

•Surgery: most cases have associated nasolacrimal duct obstruction requiring DCR.

Chronic dacryocystitis

In chronic dacryocystitis, there may be recurrent ipsilateral conjunctivitis, epiphora, and a mucocele. It may be identified by demonstration of nasolacrimal duct obstruction and expression of the contents of the mucocele. Surgical treatment is with DCR.

Conjunctiva

Anatomy and physiology 136 Conjunctival signs 137 Bacterial conjunctivitis 140 Viral conjunctivitis 142 Chlamydial conjunctivitis 144 Allergic conjunctivitis 146 Cicatricial conjunctivitis 148 Keratoconjunctivitis sicca 150

Miscellaneous conjunctivitis and conjunctival degenerations 152 Pigmented conjunctival lesions 154

Nonpigmented conjunctival lesions 156