Endonasal approach to correct nasolacrimal obstruction was described way back in 1800 by Caldwell, West and later during the begining of 1900 by Mosher. This approach was not popular because of technical limitations which included visualisation and availability of instruments for soft tissue and bone removal. Toti popularised external dacryocystorhinostomy, and this procedure was in vogue for quite sometime. The introduction of rigid nasal endoscopies kindled interest in the endo nasal approach to the lacrimal sac. The first dacryocystectomy was performed by Celsus in 50 AD. McDonogh was the first to perform endoscopic dacryocystorhinostomy in 1989.
Anatomy of lacrimal apparatus:
Knowledge of lacrimal apparatus is a must before embarking on endonasal lacrimal sac surgery. The lacrimal system consists of a superior and inferior puncta at the medial ends of upper and lower eyelids. These two drain into upper and lower canaliculi. These two canaliculi join to form the common canaliculus. This zone is known as the upper lacrimal system. The common canaliculus inturn leads into the lacrimal sac. The sac is about 12 - 15 mm long. It eventually narrows and leads into the nasolacrimal duct which drains into the inferior meatus of the nose. The naso lacrimal duct is about 18 mm long. The sac and the duct comprise the lower lacrimal system. The junction between the common canaliculus and the lacrimal sac is guarded by the Rosenmuller valve. This valve prevents tear reflux.
The nasal end of the nasolacrimal duct at the level of inferior meatus is guarded by Hasner's valve.
Physiology of lacrimal apparatus:
Tears move from the eye into the nose through a mechanism known as the lacrimal pump. Movements of the lids cause the puncta to close against each other, pushing tears into the lacrimal sac. Tears accumulating in the sac (lacrimal lake) are further pushed down into the nasolacrimal duct when the eyes open because of the relative negative pressure caused in the lacrimal lake.
Location of lacrimal sac:
A good intranasal landmark for the location of lacrimal sac is the anterior portion of middle turbinate, the sac lies just lateral to it. The lacrimal fossa is bounded by the anterior lacrimal crest, which consists of the frontal process of the maxillary bone. The posterior lacrimal crest is made up of the lacrimal bone itself.
The maxillary line is a mucosal projection along the lateral nasal wall that serves as a landmark for endoscopic sinus and orbital procedures.
Indications for Primary endoscopic dacryocystorhinostomy:
1. In the management of tearing associated with primay acquired nasolacrimal duct obstruction
2. Infection of lacrimal sac associated with primary acquired nasolacrimal duct obstruction
3. Nasolacrimal duct obstruction secondary to specific inflammatory or infiltrative disorders
4. The level of obstruction should be distal to the junction of the lacrimal sac and the duct.
5. In the management of lacrimal duct injuries associated with sinus surgeries
Contraindications of endoscopic DCR:
1. Presence of a firm indurated mass above the level of medial canthus.
2. Bloody epiphora
3. Presence of bony destruction as seen in radiological films
4. Pseudoepiphora: is essentially reflux tearing: the main gland over compensates secretion because of lack of secretion from minor glands of along the lid margin.
History & patient examination:
1. History of unilateral or bilateral tearing must be sought. Unilateral tearing mostly indicates obstructive pathology.
2. Nature of the discharge must also be sought i.e. whether clear or purulent
3. Environmental factors, such as allergies should be elicited. Medication histories are important as well as previous history of trauma or surgery.
4. On physical examination - palpate the region of the nasolacrimal sac to see if you can elicit any reflex from the puncta.
5. Eyelids should be carefully examined for evidence of excessive laxity, punctum should be examined for evidence of obstruction or inflammation. Excessively lax eyelids could cause epiphora. DCR may not help these patients.
6. The canaliculi must be probed using a Biwman probe. A hard obstruction could be caused by bone or calculi, a soft obstruction could be caused by obstruction by soft tissue. Nasolacrimal duct can be further examined by irrigating the duct with a syringe.
7. Jones test should be performed to identify the level of obstruction:
The Jones test is a test of the patency of the nasolacrimal system. The test is performed by placing fluorescein in the conjunctival sac and seeing whether or not this fluorescein can be visualized in the nose. If after a period of five minutes there is impaired outflow, it is likely that there is an obstruction somewhere in the duct or somewhere in the system. If you do not see any dye in the nose after five minutes, then you can perform a secondary test, by irrigating the duct. If after irrigating the duct no dye is found in the nose, the dye has never really reached the lacrimal sac to begin with. The obstruction is likely proximal. If you do see dye in your irrigate, then dye did reach the nasolacrimal sac, and it is likely that your obstruction is distal.
CT scan of paranasal sinuses should be taken to identify the cause of nasolacrimal duct obstruction.
This surgery can be performed either by using General or local anaesthesia. If general anesthesia is preferred, the nasal mucosa should be decongested by placement of cotton pledgets dipped in 0.05% oxymetazoline in the middle meatus, this is followed by an injection guided endscopically of 1% xylocaine with 1:200,000 epinephrine into the lateral nasal wall and middle turbinate. If local anaesthesia is preferred, topical anaesthesia is achieved by the use of pledgets dipped in 4% xylocaine mixed with 1:200,000 adrenaline to pack the nasal cavity. 1% xylocaine with 1:200,000 adrenaline is used to infiltrate the lateral nasal wall and middle turbinate for adequate anesthesia.
Localisation of lacrimal sac:
The sac must be identified endsocopically. A guide to its position is the insertion of the root of the middle turbinate on the lateral nasal wall and the maxillary line. In patients with distorted nasal anatomy following previous nasal surgeries the use of fibreoptic endoilluminator can be resorted to. This 20 guage illuminator is advanced gently through the superior or inferior canaliculus until a hard stop occurs signifying the lacrimal bone medial to the lacrimal sac is identified. The location of the sac can now be visualised endoscopically.
After localising the position of the sac endoscopically, the lateral wall mucosa is incised with a sickle knife and is elevated using a Freer elevator. It will be of immence help if this incision could be placed well anterior to the location of the sac as this will allow adequate exposure of bone. The incision is made vertically from inferior to superior. After elevation the mucosa is removed using a Blakesley forceps.
To expose the lacrimal sac, the bony lacrimal fossa must be uncovered first. The endoilluminator if used will greatly help in identifying the position of the sac. Bone removal can be performed using a Kerrison's punch forceps or by using a motor and burr. The bone removal should commence from the maxillay line and should proceed anteriorly.
Opening of lacrimal sac:
After overlying bone removal the lacrimal sac can be incised using a sickle knife. It will be helpful if an assistant could tent out the medial wall of the sac with lacrimal probes introduced through the canaliculi. The whole of the medial wall of the sac is removed. Topical mitomycin can be applied to the site of surgery to prevent restenosis of the sac.
Advantages of endoscopic dcr:
1. There is no external scar.
2. The lacrimal pump system is preserved.
3. Any concomitant intranasal pathology causing epiphora can be addressed
4. Lacrimal sac mucosa is preserved