Traverses only the involved canaliculus
Traverses both the canaliculi
Monocanalicular simple intubation
Bicanalicular nasal intubation
Stent brought out to skin through a Dacryocystostomy
Lateral stent fixation to lid margin, skin, conjunctiva, or within punctum
Greaves’ technique or pigtail probe method
Modified Quickert-Dryden method of nasolacrimal intubation
Simple Monocanalicular Intubation
Here the medial portion of the stent extends variably into the lacrimal sac and the nasolacrimal duct. The lateral portion lies at the punctum or within the canaliculus or deeper eyelid tissue (Fig. 30.1). It may also lie on the conjunctiva, skin, or eyelid margin. The stability of a monocanalicular stent depends on a snug fit into the punctum or fixation to the eyelid margin by sutures. Traditionally, an angiocath silicone glide was used for intubation of a lacerated canaliculus. Improvement was achieved by a manufactured coupling of a punctal plug (as popularized by Freeman) and a silicone rod used for lacrimal intubation (Long & Fayet), available as the Monoka and Mini-Monoka devices (FCI Ophthalmics, MA, USA) .
Schematic diagram representing a simple monocanalicular intubation
The Mini-Monaka Device
The mini-Monoka is a silicone stent that can be securely anchored at the punctum with no need for sutures. It is threaded through the punctum into the lacrimal system. As the Mini-Monoka does not feed all the way through the nasolacrimal system, it eliminates possible injury to the normal canaliculus and nasolacrimal duct.
This device consists of three components: (1) a silicone rod, which is a hollow tube 0.64 mm in external diameter and 27 cm long; (2) a superior fixation device (SFD), which allows for a secure seating of the punctal plug part of the device in the ampulla; and (3) a seating instrument, which can either be a metallic or a plastic probe point to push the plug securely into the punctum.
The superior fixation device has a collaret, which is wider than the lacrimal meatus to prevent burying or migration of the Monoka into the canaliculus. It is the only part of the device which is visible once the Monoka has been properly placed in the lacrimal duct. It permits postoperative evaluation and simple removal when appropriate. Three sizes of collarets are available. These are fused to a bulb, which forms the inferior part of the SFD. When the Monoka is in place, the bulb is securely fixed in the ampulla. Its bulbous shape prevents the spontaneous extrusion of the SFD. Yet its size is not so wide that it would prevent simple removal when desired. The silicone tubing is fused together with the bulb, forming a right angle (Fig. 30.2). The Mini-Monoka device does not require a probe to be inserted into the nasolacrimal duct as it has a solid silicone rod. Placement of this device requires gentle punctal dilation. The proximal part of the punctum and canaliculus is intubated with the free silicone rod part of the device, which is brought out via the wound. Then a smooth pulling of the free silicone part of the Mini-Monoka allows the SFD to set into the punctum. The punctal plug seating delivery device may sometimes be needed. The end of the rod is then shortened sufficiently to pass into the distal canalicular wound and the lacrimal sac. Since these are commonly used for canalicular lacerations, sutures are carefully placed to close the canalicular wound and to reconstruct the canthal tendon by standard techniques (Fig. 30.3a– l). The average duration of intubation following trauma is 3 months . Removal of the stent is simple and is accomplished by pulling out the collaret with a forceps.
The Mini-Monoka stent
Technique of insertion of a Mini-Monoka stent for lower canalicular laceration. Identification of the lateral cut end of the canaliculus (a). Identification of the medial cut end (b). Probe through the medial cut end (c). Confirming hard stop with the probe (d). Mini-Monoka pass through the punctum (e). Retrieval through the lateral cut end (f). Securing the SFD at the punctum (g). The pass of Mini-Monoka through the medial cut end (h). Approximating the two cut ends of the eyelid (i, j). Securing with a suture (k). The completed lid repair with a snugly fitting Monoka (l)
Self-Threading Monoka Over a Ritleng Probe
The self-threading Monoka (Ritleng style) tube (Fig. 30.4) is attached to a thin thread-guide, which is fed through a Ritleng probe and gently out the nose. The probe is then removed, and the thread-guide is pulled along with the silicone tubing into proper position in the nasolacrimal duct. The tube is securely anchored at the punctum by the SFD. Intubation can be a complicated process in infants and small children, as the nasal passages are compact with narrow anatomical confines. The removal of a thin suture or thread-guide from the nose is easier and less traumatic than traditional metallic probes, facilitating canalicular procedures in young children.
Monoka over a Ritleng probe
The Monoka-Crawford (Fig. 30.5) can be used for monocanalicular repairs, DCR with agenesis or proximal obstruction of one canaliculus, pre-saccal stenosis, or partial nasolacrimal duct obstructions. This stent feeds all the way down into the nasolacrimal duct, and unlike the Mini-Monoka, it is anchored at the punctum by the SFD and then retrieved using a Crawford Hook.
Monoka-Crawford intubation set
The Masterka Device
Designed by Oculoplastic surgeon Bruno Fayet, the Masterka offers a safer and faster intubation of tear ducts as it does not require the frequently difficult step of recovery inside the nasal cavity . Unlike the traditional “pulled” technique in which the stent is advanced through the nasolacrimal system and retrieved through the nose by pulling on the guide probe or thread, the Masterka has no metallic probe or suture attached to it and, therefore, it is not pulled out of the nose. Instead, the Masterka is pushed into the nasolacrimal duct and anchored in place at the punctum by a plug-like fixation head similar to Monoka stents. A pushed intubation is more similar to a simple probing than a pulled intubation and significantly reduces time for the intubation procedure. The Masterka device consists of a silicone tube moulded to a fixation head and premounted on an introducer to facilitate insertion (Fig. 30.6). The introducer is easily and completely removed once the intubation of the lacrimal passages has been completed. The Masterka comes in three different lengths of 30, 35, and 40 mm.
Masterka Device mounted on the inserter
In a monocanalicular–annular stent placement, the lacrimal stent is passed through the length of the involved canaliculus only and into the lacrimal sac. The stent is then exteriorized to the skin through the wall of the sac and the medial end of the stent may be tied to the laterally protruding end in the form of a “sling.”  (Fig. 30.7) In addition to silk, various materials used for these monocanalicular–annular stents included chromic gut, nylon suture, and polyethylene tubing. However, with the advent of the Mini-Monaka, the annular technique of monocanalicular stenting has taken a backseat.
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In this “closed loop” system, it is possible to expose only a short segment of the stent between the superior and inferior puncta or canaliculostomy, and is therefore to a certain extent protected from extrusions .
In bicanalicular–annular stent, both the canaliculi are occupied as a part of a continuous loop. The lateral portion of the loop lies between the lacrimal puncta and the medial portion is united to itself in the common canaliculus or the lacrimal sac (Figs. 30.8 and 30.9). Stallard cited Greaves’ technique of bicanalicular–annular stenting using a nylon suture over a lacrimal cannula . Pigtail probes have also been used for annular stent placement . The ends of the stent can be secured with a suture or a sleeve. The flexibility of silicone allows it to be tied to itself in a knot between the punctae . Alternatively, the ends of the tubing may be tied and fixated away from the eye to the skin of the canthus [27, 28]. Marube recommended placing a nylon thread within the lumen of the silicone tube along its entire length and then tying the nylon . The united ends of the tube can then be rotated into the canaliculus (Figs. 30.8 and 30.9). Self-retaining stents are an example of bicanalicular–annular intubation.
A patient with bicanalicular–annular intubation (Photo courtesy: Dr Gangadhar Sundar, Singapore)
Self-retaining stents made of silicone are a recent development (Fig. 30.10). They consist of a silicone tube in three different lengths (25, 30, and 35 mm) to cover for patients anatomical variations and two flexible anchoring ends designed to stabilize the stent into the common canaliculus. The outer diameter of the silicone tube is 0.64 mm. It has a central reference marking that offers control over proper positioning. Each end has two flexible flaps that fold inward during insertion through the punctum. Flaps open at the lacrimal sac for secure fixation. The flaps fold backward upon removal of the stent.
Bicanalicular Nasal Stent
In a bicanalicular nasal stent, both canaliculi are occupied as a part of a continuous loop. The lateral portion of the loop lies between the lacrimal puncta and the medial portions of the stent together pass down the nasolacrimal duct to be fixated within the naris (Fig. 30.11). Passing one arm of the stent from the superior canaliculus to the nose and the other arm from the inferior canaliculus to the nose does this.
Schematic diagram of bicanalicular nasal intubation
The Crawford Bicanalicular Nasal Intubation System
The Crawford Bicanalicular Intubation attaches to a metallic glide with an olive tip that is fed through the system and retrieved below the inferior turbinate using a Crawford Hook (Fig. 30.12). This is a simple procedure designed by the Crawford, which speeds up the process of inserting a lacrimal stent with less trauma and tearing of the nasal floor. The Crawford Intubation set comprises of two flexible stainless steel wires 0.40 mm in diameter and a hollow silicone tube with an outside diameter of 0.64 and a 0.30 mm lumen. The stainless steel wires have olive-shaped tips for grasping with a special retrieval hook and permit ease of extraction from the inferior meatus of the nose (Fig. 30.12).
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