Terminology and Classification
A DCR is the creation of a fistula from the lacrimal sac into the nose. Its main use is when there is distal outflow obstruction to the nasolacrimal system. It is important that with the history and examination including syringing and probing the correct diagnosis is made.
One of the most important aspects of this surgery is to first make sure that the primary pathology is due to distal obstruction of the nasolacrimal system. If there is proximal obstruction, then surgery will fail.
Often distal obstruction is mixed with a varying degree of proximal obstruction and this needs to be taken into consideration when counseling the patient about their expectations from surgery. Syringing and probing is the main way to define the site of obstruction.
A dacryocystogram is indicated if there is any mass within the sac. Scintigraphy helps to define a functional problem. A bloody discharge from the punctum is a symptom that needs investigating to exclude malignancy in the sac. The common symptoms are epiphora, recurrent dacryocystitis, or swelling from a mucocele. Epiphora causes not only tearing but an alteration in refraction that requires the patient to repeatedly blink or wipe their eye. Its prevalence is much more common with aging. It is unusual for intranasal pathology to be responsible, but conditions such as Wegener granulomatosis and sarcoidosis can affect this. Nasolacrimal duct obstruction can occur following a middle-third facial fracture. When this is the case, it can pose a surgical problem as the bone in the region of the lacrimal fossa may be thicker owing to callus formation or a concertina effect of the facial bones. Distal nasolacrimal obstruction can also occur secondary to endoscopic sinus surgery if back-biters used to remove the uncinate process are used too far forward. A contraindication to DCR is the presence of a benign or malignant lesion in the lacrimal system or the surrounding tissues and active Wegener granulomatosis.
Endonasal DCR can be done under local or general anesthesia. It is possible to open the lacrimal sac endonasally with either conventional instruments or a laser. The laser procedure has the advantage that it can be done more readily as a day-stay procedure as there is a minimal amount of bleeding. The disadvantages of the laser are its expense, the precautions that need to be taken, and the fact that the results are not as good as with conventional instruments. One technique that will help the operator to find the site of the lacrimal sac and the lacrimal bone is to insert a rigid light-pipe through the upper punctum and canaliculus and angle it down into the sac. The site of the lacrimal fossa can then readily be identified endonasally by seeing the discrete pinpoint of light, and this will help the operator define where the bone is thinnest in the lacrimal fossa. In approximately 8% of patients there is an agger nasi cell in this area and the light will be more diffuse. Very occasionally, the light is difficult to see and then the light on the endoscope can be turned off to help define where the bone is thinnest. If the light is diffuse and there is an agger nasi air cell, it will be necessary to open this up and go through it before going through the lateral wall and the lacrimal bone into the sac. It is best not to open the sac very high up without also opening it inferiorly, as a sump can form that collects mucus and can predispose to recurrent infection. If the procedure is done under local anesthesia, amethocaine drops are placed in the eye, followed by a nasal pack (1 cm ribbon gauze or a patte soaked in cophenylcaine or 6% cocaine) and an injection of 1% lignocaine injected through the surface of the conjunctivaaround the sac. The latter may look alarming to the novice, but the conjunctiva is well anaesthetized with topical anesthetic drops. Discomfort can be minimized by injecting slowly to avoid pressure and by warming the local anesthetic to near body temperature. Local anesthetic is injected around and not into the lacrimal sac. After 2 minutes, a subcaruncular injection will help anaesthetize the bone around the lacrimal fossa. This is followed up 5 minutes later with an injection of 1% lignocaine and 1:200000 epinephrine intranasally where the rhinostomy is to be made.
Endoscopic Marsupialization of the Sac with Conventional Instruments
The best way to expose the lacrimal sac with conventional instruments endoscopically is to incise the mucosa on the lacrimal crest, producing a posteriorly based flap. The anterior lacrimal crest is thick white bone, and the surgeon may recognize it as being the hard bone that they first approached with a sickle knife when they tried to perform a conventional uncinectomy and found that they could not incise this area. When a mucosal flap has been reflected, the white hard bone of the anterior lacrimal crest is readily seen and palpated. It is possible to remove this using a Kerrison or sphenoid punch, which can remove the greater part of it in three or four bites. In order to obtain a large ostium, the upper part of the lacrimal crest also needs to be removed. In a child this can be removed with a sphenoid punch, but in an adult a coarse diamond burr is needed to remove it as it is very thick. This exposes the lacrimal sac more widely, to the extent that the common canaliculus can often be seen. Just posterior to the hard lacrimal crest lies the uncinate process, and just lateral to that the thin bone that forms the medial aspect of the lacrimal fossa. The very thin bone over the lacrimal sac can easily be removed as it is paper thin. The sac has a magenta hue, and it can be divided vertically with either a sickle knife or a 45° beaver scalpel. Placing a probe within the sac will help tense it medially and make incision into it easier. Microscissors can be used inferiorly and superiorly to create anterior and posterior flaps from the lacrimal sac. Alternatively, a punch can be used to enlarge the rhinostomy. These flaps of sac mucosa can then be placed in continuity with the mucosa of the nasal wall in order to avoid cicatrization and help maintain a patent rhinostomy. Stents are placed in position for 6−8 weeks.
Some surgeons do not insert a stent, while others leave a stent in for several months. In our hands, the success rate of a laser DCR has been worse if we have removed the stents within 8 weeks. If we leave the stents in for longer than 3 months, the incidence of granulations around the tube is increased. In an endoscopic DCR using conventional instruments, the rhinostomy requires no stents if it is wide open.