AIM:To compare the canalicular diameter when eyes opened and closed using ultrasound biomicroscope. METHODS:Twenty volunteers(20 eyes)with nasolacrimal duct obstruction were included. The lower canaliculus of one eye in every volunteer was detected and measured with ultrasound biomicroscope when eyes opened and closed. Before measurements sodium hyaluronate was injected through the upper lacrimal puncta until it overflowed from the lower lacrimal puncta. The length of the vertical canaliculus, anteroposterior diameter of the vertical canaliculus at the proximal, middle, distal, anteroposterior diameter and vertical diameter of the horizontal canaliculus at the proximal, middle, distal were measured. According to elliptical area formula S=πab(a =1/2 anteroposterior diameter,b=1/2 vertical diameter), transverse area of the horizontal canaliculus at the distal, middle and proximal were calculated. The differences of measurement when eyes opened and closed were compared by paired t test. RESULTS:When eyes opened and closed, the length of vertical canaliculus of inferior canaliculus were respectively 2.56±0.33 and 2.76±0.34mm; anteroposterior diameters at the distal part were respectively 0.29±0.04 and 0.32±0.04mm; those at the middle were respectively 0.32±0.03 and 0.35±0.04mm; those at the proximal were respectively 0.38±0.02 and 0.40±0.04mm and those differences between opened and closed eyes were statistically significant(t=-5.346, -5.12, -4.94, -4.682; P2; those at the middle were respectively 0.67±0.04 and 0.75±0.08mm2; those at the proximal were respectively 0.51±0.10 and 0.56±0.15mm2 and those differences between opened and closed eyes were statistically significant(t=-7.453, -6.73, -6.43; PCONCLUSION:Compared with the opened eyes, the vertical length of lower canaliculus become shorter, the anteroposterior diameter of vertical canaliculus and transverse areas of horizontal canaliculus become smaller.
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