[Preliminary study on CT retrograde intubation dacryosystography (CT-RIDC) and its impact factors]

To observe practicality and safety of CT-RIDC for the patients with presaccular lacrimal obstruction and study the related factors. To provide guidance for the diagnosis and treatment of the patients with presaccular lacrimal obstruction.

Fifty-four patients (75 eyes) with presaccular lacrimal obstruction, including 3 cases (5 eyes) of upper and lower lacrimal punctum atresia, 15 cases (24 eyes) of superior and inferior canalicular obstruction, 18 cases (28 eyes) of common canaliculus obstruction, 18 cases (18 eyes) of old laceration of superior and inferior canalicular, were recruited. All patients underwent the examination by using 0° and 30° ear endoscope and the imaging characteristics of the inferior orifice of nasolacrimal duct were obtained. Fifty-three cases (65 eyes) with the opening inferior orifice were randomly divided into four groups (15 eyes, 17 eyes, 17 eyes, 16 eyes) according to different angle of head hypsokinesis in the supine position. The OM lines back along the sagittal plane of the head back 10°, 20°, 30°, 40° were measured. The angles of head hypsokinesis were set in accordance with the OM line measurement results.Intubation was successful when the intubation guided needle within the set of epidural anesthetic catheter aided with endoscopy was inserted into the inferior orifice of nasolacrimal duct and then the epidural anesthetic catheter was inserted into the lacrimal duct 6 mm. The angle (θ) between the long axis of the curved part of the intubation guided needle and the long axis of the guided needle was measured. The numbers of intubation success cases in each group were recorded.χ² test was used to compare intubation success rate under the different angle of head hypsokinesis.Scheffe method was used to compare intubation success rate between each group. Contrast medium was then injected into lacrimal duct through the epidural anesthetic catheter for patients with successful intubation and CT scan was carried out. 3D model of lacrimal passage was reconstructed with CT axial scanning.

The intubation guided needle was successfully inserted into the inferior orifice of nasolacrimal duct in 44 eyes among 65 eyes with the opening orifice. The number of successful intubation cases were 4 eyes, 15 eyes, 13 eyes, 12 eyes and the intubation success rate was 26.67%, 88.24%, 76.74%, 75.00% according the angle of head hypsokinesis 10° group (15 eyes), 20° group (17 eyes), 30° group (17 eyes), 40° group (16 eyes). The intubation success rate of head hypsokinesis 10° group was significantly lower than that of the other groups. Multiple Comparison by Scheffe Test demonstrated that there was a remarkable difference (P < 0.05) in the intubation success rate between head hypsokinesis 10° group and the other three groups. There were no significant differences in the intubation success rate among head hypsokinesis 20° group, head hypsokinesis 30° group and head hypsokinesis 40° group. The mean of θ was 108° with a range of 93.2°-120.5° by measuring the angle θ of the successful intubation cases. According to the frequency distribution plot, most θ was in 104°-115°. The successful intubation cases (44 eyes) underwent CT scan in the same position immediately after injected contrast medium (Optiray) through the epidural anesthetic catheter. CT images of 28 eyes showed retained contrast medium in the nasolacrimal duct and lacrimal sac. The findings from CT-DCG images were basically agreed with the operation.

CD-RIDC may apply to pre-operative examination for the patients with the opening orifice and presaccular lacrimal obstruction.It provideed imaging evidence for diagnosis and therapy and it was safe and practical. Many factors could affect CD-RIDC. The main verified facors were the shape of the inferior orifice of nasolacrimal duct, head position of the patient and the bending angle of the tip of intubation guided needle.