Normally, the tears drain through two minute openings at the inner end of the lid margins, known as the upper and lower lacrimal puncta.
Most of the tears drain through the lower punctum. The puncta mark the opening of the lacrimal canaliculi and these small tubes conduct tears medially to the common canalicu lus and thence into the tear sac (Figure 5.1). The tear sac is connected directly to the naso-lacrimal duct, which opens into the inferior meatus of the nose below the inferior turbinate bone. The lacrimal puncta are easily visible to the naked eye and, in the elderly, the opening of the lower punctum can appear to project upwards like a miniature volcano. Inadequate drainage of tears can result from displacement of the punctum; the lower lid in the elderly sometimes becomes turned inwards (entro-pion) because the whole tarsal plate rotates on a horizontal axis (Figure 5.2). This, in turn, is caused by slackening of the fascial attachments of the lower margin of the tarsal plate. At first, the eyelid turns in whenever the patient screws up the eyes but, eventually, the lid becomes permanently turned in so that the lashes are no longer visible externally and rub on the cornea. Such patients complain of watering, sore eyes and the matter can be corrected effectively by eyelid surgery. Entropion can also result from scarring and contracture of the conjunctiva on the inner surface of the eyelid.
Not only can the punctum become turned inwards, but it can also be turned outwards. Sometimes the eversion is slight, but enough to cause problems. The patient might have been using eyedrops, which, combined with the overflow of tears, sometimes causes excoriation and contracture of the skin of the lower eyelid. This leads to further eversion or ectropion of the lower eyelid (Figure 5.3). Often, the ectropion arises as the result of increasing
Figure 5.3. Ectropion.
laxity of the skin in the elderly but it might also result from scarring and contracture of the skin caused by trauma (cicatricial ectropion). Ectro-pion can be corrected effectively by suitable lid surgery.
Drainage of tears along the lacrimal canali-culi depends to some extent on the muscular action of certain fibres of the orbicularis oculi muscle. This band of fibres encloses the lacrimal
Figure 5.3. Ectropion.
sac and it is thought that the walls of the sac are thereby stretched, producing slight suction along the canaliculi. Whatever the exact mechanism, when the orbicularis muscle is paralysed, the tear flow is impaired even if the position of the punctum is normal. Sometimes patients who have suffered a Bell's palsy complain of a watering eye even though they appear to have otherwise made a complete recovery.
Misplacement of the drainage channels, particularly of the punctum, can thus affect the outflow of tears, but perhaps more commonly the drainage channel itself becomes blocked. In young infants with lacrimal obstruction, the blockage is usually at the lower end of the naso-lacrimal duct and takes the form of a plug of mucus or a residual embryological septum that has failed to become naturally perforated. In these cases,there is nearly always some purulent discharge, which can be expressed from the tear sac by gentle pressure with the index finger over the medial palpebral ligament. The mother is shown how to express this material once or twice daily and is instructed to instil antibiotic drops three or four times daily. This treatment alone can resolve the problem and many cases undoubtedly resolve spontaneously. Sometimes it is necessary to syringe and probe the tear duct under a short anaesthetic. Usually one waits until the child is at least nine months old before considering probing. In adults, the
obstruction is more often in the common canaliculus or nasolacrimal duct. In these cases the tear duct can be syringed after the instillation of local anaesthetic drops. This procedure is simple, although it must be done with care to avoid damaging the canaliculus, and even if the obstruction is not cleared, it can allow the surgeon to identify the site of the obstruction. Sometimes a permanent obstruction is identified at the lower end of the nasolacrimal duct, which can be relieved by surgery under general anaesthesia or the more recently introduced laser treatment applied through the nose. The initial investigation of lacrimal obstruction entails syringing and if this does not give the information required, it is possible to display the tear duct by X-ray using a radio-opaque contrast medium. This is injected into the lower canaliculus with a lacrimal syringe (Figure 5.4). The technique is known as dacryocystography.
Sometimes the lacrimal sac can become infected. This can occur in children or adults but is more common in adult females. The condition might present initially as a watering eye and, in its early stages,the diagnosis can be missed if the tear sac is not gently palpated and found to be tender. Subsequently, there is marked swelling and tenderness at the inner canthus and eventually the abscess can point and burst. In its early stages, the condition can be aborted by the use of local and systemic antibiotics, but once an abscess has formed this can point and burst on the skin surface. Surgical incision and drainage of a lacrimal abscess can lead to the formation of a lacrimal fistula (Figure 5.5).
Rarely, the lacrimal canaliculi can become infected by the fungus Actinomycosis and a small telltale bead of pus can be expressed from the punctum. The condition is resistant to ordinary treatment with local antibiotics, and is best treated by opening up the punctum with a fine knife specially designed for the purpose -the procedure being called canaliculotomy -and then irrigating the canaliculi and tear duct with a suitable antibiotic.
The diagnosis of lacrimal obstruction therefore depends firstly on an examination of the eyelids, secondly on syringing the tear ducts, and then if necessary dacryocystography. Figure 5.6 illustrates the diagnostic use of lacrimal syringing.
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