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The human VSX1 is required for cone ON bipolar cell function but not for rod and cone OFF bipolar cells, giving a unique example of such a selective heritable retinal defect in humans. Furthermore, the authors provide the first clinical support for a new alternative role of VSX1 in cone biology, probably similar to that proposed for its goldfish ortholog during retinal differentiation.

The authors conducted a retrospective study on 120 consecutive cases of nasolacrimal duct obstructions (NLDO) in 85 children, operated on by a single surgeon (BF) from January 1988 to July 1992. Mean age at the time of surgery was 5.4 years (1 to 11 years). Seventyseven bicanaliculo-nasal intubations (BCNI) and 43 monocanaliculo-nasal intubations (MCNI) were performed. MCNI were performed using the Fayet-Bernard 'MonoKa' tubing material (FCI, Paris, France). This device permits monocanalicular intubation with meatic fixation by a punctum-plug-like extremity. Among MCNI, 39 were placed into the superior canaliculus. Nine MCNI were indicated because of a true monocanalicular agenesis (inferior canaliculus agenesis in five cases and superior canaliculus agenesis in four cases).Mean follow-up was ten months. Average duration of intubation was seven months for BCNI and 5.1 months for MCNI. BCNI and MCNI resulted in complete resolution of the epiphora in 62.2 and 67.6% of cases respectively.Intermittent tearing was observed post-operatively in 30.1% of BCNI and 23.5% of MCNI. Permanent tearing was present in 7.5% of BCNI and 8.8% of MCNI.Complications associated with BCNI were observed in 20.7% of cases and occurred an average of 96 days post-operatively. These complications included the loss of tubing (I .3Vo), stricturotomies (2.6V0), and non-reducible exteriorization of tubing (16.8%).Complications associated with MCNI were noted an average of 109 days post-operatively in 25.5% of cases. These complications included two cases (4.7%) of pyogenic granuloma, of which one was associated with the loss of the tubing. One case (2.3%) of superficial corneal erosion, eight cases (18.6%) of exteriorization resulting in loss of tubing and one case of intracanalicular migration of the tubing were also observed with MCNI. Functional results obtained with BCNI and MCNI for NLDO are comparable. However, complications associated with MCNI may be anatomically less damaging given the absence of stricturotomy.

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