Computed tomographic dacryocystography combined with multiplanar reconstruction technique in lacrimal duct probe placement

CT dacryocystography (CT-DCG) combined with multiplanar reconstruction (MPR) enables precise evaluation of the bony nasolacrimal duct (BNLD) anatomy, which may guide surgical treatment for nasolacrimal duct obstruction (LNDO). This retrospective study aimed to identify key anatomical factors influencing lacrimal probe placement and to assess whether preoperative imaging improves clinical outcomes. Between December 2018 and January 2022, 230 patients (257 eyes) with LNDO underwent CT-DCG and MPR before planned lacrimal probing and intubation. Reconstructed images were used to measure BNLD angle, diameter, length, and the spatial relationship between its long axis and the forehead soft tissue and frontal bone. Probe insertion success was recorded intraoperatively. Postoperative outcomes were evaluated in a subset of 78 patients (78 eyes) at 6 months using Munk score and lacrimal irrigation, defining success as complete (Munk 0–1 + irrigation return < 50%) or partial (Munk 2–3 or return < 50%). Probe insertion succeeded in 246 eyes and failed in 11 eyes (10 patients). The failed group had a significantly smaller angle between the BNLD long axis and the coronal plane (NC angle) (P < 0.05). At 6 months, complete success was achieved in 59/78 eyes (75.6%), partial success in 3/78 (3.8%), and failure in 16/78 (20.5%); overall effectiveness was 79.5%, similar to reported intubation rates. Successful intraoperative probe placement was associated with no overlap or < 2/3 overlap of the BNLD axis with forehead soft tissue. The mean NC angle was 19.1°; 66% of BNLDs were inwardly oriented (mean 7°). CT-DCG with MPR provides detailed BNLD anatomy and can predict difficult probe placement, potentially reducing false passages. However, its impact on long-term symptomatic success is comparable to conventional probing, and its main value lies in preoperative planning and avoiding unnecessary attempts.