Assessment of lacrimal resistance using a manometric tear duct irrigation system

Lacrimal surgery aims to provide a low-resistance tear drainage passage. An assessment of lacrimal resistance guides decisions on surgery. We present results of a modified tear duct irrigation system that reliably measures lacrimal outflow resistance. Patients in a specialist lacrimal clinic had a full work-up to the point of tear duct syringing. The tear ducts were irrigated using a manometric system, which applied a fixed, known head of fluid pressure to a lacrimal cannula. Fluid flow is recorded and the lacrimal resistance derived as fluid pressure/fluid flow (units cmH20 secml-1, for simplicity presented as drops per minute, dpm). Patient groups were: A: Asymptomatic, A1: subgroup where the fellow symptomatic eye had a visible cause for watering, B: external visible cause for watering (ocular surface/lid/punctum), C: no externally visible cause, D: post op DCR, E: post syringing and probing, F: mixed/other. 444 tear ducts were examined. Mean flows (dpm) were: A1 (n = 19) 55; B (n = 183) 46; C (n = 142) 22: D (n = 38) 52. Excluding complete obstruction (n = 29), tear duct syringing only detected 48% of those with impaired manometric flow. Of those with a normal tear duct syringing, 53% had impaired manometric flow; 34% had a flow of 0 dpm. Differences in A1 versus C; B versus C and pre versus post dacryocystorhinostomy were all statistically significant (p < 0.05). The manometric system presented reliably measures lacrimal resistance and provides a substantial increase in sensitivity and specificity over conventional lacrimal syringing.