Monocanalicular versus bicanalicular intubation in the treatment of congenital nasolacrimal duct obstruction

Silicone intubation was first described by Quickert and Dryden in 1970 and the procedure has become part of the standard management of CNLDO [2, 3, 6]. Among the factors that affect the treatment success of CNLDO are age, severity of symptoms, the history of previous interventions, time of the interventions, and compliance with treatment. However, there are no generally accepted and defined rules concerning age, length of intubation, and/or different variations in intubation systems [6, 11].

Although tube placement in children requires general anesthesia, the normal anatomy of the lacrimal system is not destroyed, and the success rates range from 80% to 100% [1‐3, 6, 12]. BCI has been used more frequently, not only for treatment of CNLDO, but also for dacryocystorhinostomy, canalicular stenose, etc. [2, 6].

One of the factors that may determine whether or not to use BCI or MCI is the number of complications [1‐3, 6]. One of the main advantages of BCI is that BCI is generally very well-tolerated by the cornea because it is significantly smoother than MCI [1, 7, 9]. If MCI is used, corneal abrasions or ulcers can be caused by the ocular end of the MCI. The abrasions usually occur in the inferior nasal quadrant (if the tube is fixed in the the inferior canaliculus), and usually heal in a few days after local treatment [9]. Fayet et al. observed only three (1.5%) corneal ulcers in 223 eyes with MCI, whereas no corneal ulcers were observed in 1,620 BCI placements [9]. They assumed that the placement of the MCI in the superior canaliculus is a predisposing factor for corneal irritation, especially if the size and length of the collarete is larger [9]. On the other hand, Engel et al. recommend performing MCI through the superior canaliculus, and found only a 2% risk of conjunctival or corneal abrasions in their series of 635 eyes [3]. In our study, in which monocanalicular tubes were inserted into the inferior canaliculus, corneal abrasion was observed in only one child (2.8%) a few days after the surgery. The abrasion healed within 3 days without the premature removal of the tube. Our experience confirms that it is necessary to use tubes of an appropriate size with a small flange (collar) that does not exceed the eyelid margin and does not irritate the cornea, so that corneal abrasion and ulceration is prevented. Conversely, Fayet et al. found the diameter of the collar to be unimportant and without influence on the rate of corneal erosions [7].

MCI offers a chance to achieve better success rates than simple probing, and requires only a single pass through the nasolacrimal system [3]. The technical insertion of MCI as well as its removal is easy, and the difficulties associated with BCI are minimized [1, 4]. Based on our 17 years of experience with lacrimal surgery, we agree that the manipulation in only one canaliculus may be advantageous because the risk of possible iatrogenic traumatisation of the lacrimal system is lower.

Unexpected side-effects should be taken into consideration, too. While we observed no granuloma pyogenicum in the BCI group, we observed two granulomas in children who had MCI. Though these occurences resolved a few weeks after removal of the tube, they seem to be related to the ocular end of MCI. Fayet et al. recommended not leaving a MCI in for longer than 3 months to decrease the likelihood of complications [9]. While we usually removed MCIs within 3 to 4 months after placing the tubes, the question of whether or not the number of complications would increase with longer MCI placement is unclear. In our study, there were only two children with a longer (5 and 11 months respectively) tube placement (they did not return for removal of the tube until these times); however, no complications were observed in these two cases, and full success was achieved.

In order to prevent damage to the punctum and fibrous meatal ring while inserting the MCI, an appropriate technique should be used [7]. That is why performing an excessively aggressive dilation of the punctum is not recommended. Fayet, who developed the Monoka system (FCI, France), recommends only gentle traction on the distal end at the time of insertion and gentle dilation of the punctum [7, 9]. A special dilator for inserting the tube can help to avoid inadvertent damage to the puntal and canalicular systems [7]. Although we did not use this dilator, no difficulties during the time of tubing were observed.

On the other hand, excessive dilation might increase the incidence of some complications, especially spontaneous loss of the tubing [7]. This complication was observed in 35.4% in a study of 48 eyes with CNLDO treated with MCI reported by Kaufman and Guay-Bhatia, where premature removal was observed in 21 of 48 eyes (43.7%) [1]. Our results did not confirm these findings. Dislodgement of BCI causing premature removal was observed in four eyes, whereas premature loss of the monocanalicular tube was observed twice.

Few reports compare the success rates of MCI with BCI. The success rates of BCIs for the treatment of CNLDO range from 83% to 100% [2, 6, 11, 12]. Feyet et al. observed complete resolution of epiphora in 67.7% with Monoka and 62.4% with BCI in their study of 120 cases [13]. In their study comparing MCI and BCI in 48 eyes of adults, Kashkouli et al. achieved nearly the same complete success rate (MCI 61.5%, BCI 59.0%); moreover, higher partial success and lower failure rate was achieved than in the group with BCI [4]. In our study, we found no significant differences in the sucess rates between the BCI (88.5%) and MCI (97.1%) groups. On the other hand, in the study by Kaufman et al. of 48 eyes with MCI, full and partial success was achieved in only 30 cases (78.0%), and 21 cases of premature tube removal occurred (43.7%) [1]. In the study by Engel et al. of 635 children with probing and MCI, the success rate was 97%, declining to 90% when surgery was performed in infants older than 24 months of age [3]. We agree with Engel et al. that, for those patients with CNLDO requiring general anesthesia, MCI may reduce recurrence and reoperations, and is an appropriate alternative in the treatment of CNLDO [3].

Our results raise the question of whether or not it would be better to prefer MCI over BCI in the treatment of CNLDO. Although our study supports a preference for MCI, further prospective, randomised studies would better determine the advantages and disadvantages of the two intubation methods.