Hydrostatic pressure changes during simulated lacrimal sac massage on a congenital nasolacrimal duct obstruction(CNLDO)modelOA

Objective:Congenital nasolacrimal duct obstruction(CNLDO)affects 5%-20%of infants.Lacrimal sac massage is considered the first-line therapy for CNLDO,yet there is a lack of quantitative comparisons among different massage techniques.The aim of this study is to quantitatively evaluate the changes in hydrostatic pressure at the inferior nasolacrimal duct(NLD)orifice during the application of different lacrimal sac massage techniques for CNLDO,using a validated simulation model.Methods:This was an experimental biomechanical study that used a CNLDO model equipped with sensors.The simulation was conducted in a laboratory setting at an academic ophthalmology center.First,seven expert ophthalmologists validated the model,and then three of them performed the massage techniques.A total of four massage techniques were applied:Technique Ⅰ(Horizontal),Technique Ⅱ(Vertical),Technique Ⅲ(45°Oblique),Technique Ⅳ(Crigler’s,inferomedial).The primary outcome measure was the hydrostatic pressure(mmHg)at the lower NLD orifice during the application of each massage technique.Secondary measures included force vectors and the degree of compression of the common canaliculus.Results:The Crigler’s technique(Ⅳ)generated the highest median and maximum hydrostatic pressure at the lower NLD orifice,followed by Technique Ⅲ(45°oblique).In contrast,Techniques Ⅰ and Ⅱ produced significantly lower pressures.Sensor data collected during the application of maximal Crigler’s pressure(0.7 N at NLD orifice)showed several key findings.There was a concurrent force>0.3 N over the common canaliculus,which effectively prevented reflux.Additionally,there was a rapid application of a 1.9 N force over the lacrimal sac directed inferomedially,resulting in a 0.2 N pressure at the sac/NLD junction.During the generation of maximal Crigler’s pressure:1)A force of 0.7 N was recorded at NLD orifice;2)There was a concurrent 1.9 N inferomedial force applied to the lacrimal sac.3)A pressure of 0.2 N was measured at the sac/NLD junction.In all applications of Crigler’s technique,the compression of the common canaliculus remained>0.3 N,which is the threshold for preventing reflux.Conclusions:This quantitative study demonstrates that Crigler’s lacrimal sac massage generates significantly higher hydrostatic pressure at the lower NLD orifice compared to alternative techniques,while simultaneously maintaining a compression of the common canaliculus that prevents reflux.These findings provide biomechanical evidence to support the use of Crigler’s technique as the optimal massage method for the treatment of CNLDO.Clinical adoption of this technique may lead to improve rates of obstruction clearance and a reduced need for invasive procedures.