Dacryocystography (DCG) has been used to exclude areas of narrowing or stenosis, and if the lacrimal system is patent, dacryoscintigraphy (DCS) is use to define the level of outflow delay [1, 13]. Wearne et al. [14] studied the feasibility of DCG and DCS in patients with FNLDO and showed that when used together, they have a high sensitivity of 98 %. Montanara et al. [3] described outflow difficulties of contrast medium without anatomical narrowing as characteristic features on DCG. Hurwitz and Welham [6] divided the functional abnormalities radiologically at two levels: upper part (orbicularis, puncta, canaliculi) and lower part (sac, duct, inferior meatus). Chan et al. [1] further refined these as those with pre-sac and post-sac delay. Francis et al. [15] showed increased tear meniscus height in FNLDO using videoreflective dacryomeniscometry but found no statistical difference was noted when compared with PANDO, making it a nonspecific diagnostic tool.

The author of this chapter believes that with the advent of dacryoendoscopy, it would be easier to identify any anatomical narrowing or stenosis. Since the management does not differ markedly, exclusion of anatomical abnormalities with demonstrable patent lacrimal passage should be sufficient for a diagnosis in a routine practice.

The management of functional epiphora is controversial, and no consensus has evolved over the last six decades since its first description in 1955 [2]. One of the fundamental reason for this is the variations in terminologies exclusion criteria and management. Do these patients really need treatment? Evidence suggests in the affirmative. Cheung et al. [7] conducted a detailed study on 33 FNLDO patients and studied their symptoms in relation to the vision, reading, driving, moods, work, and embarrassment. All these parameters were affected specifically vision, reading, and embarrassment, resulting in lower quality of life. Overall symptom scores significantly reduced after dacryocystorhinostomy (DCR) from a mean preoperative score of 3.50 (SD = 2.07) to 2.0 (SD = 1.65) in the postoperative period (p < 0.05).

Lacrimal pump failures with severe symptoms can be candidates for a conjunctivodacryocystorhinostomy, or CDCR, with Jones tubes [16]. These tubes have also shown to benefit persistent epiphora following a patent DCR [16, 17]. There is an increasing evidence of benefits of silicone intubation (SI) in FNLDO patients [4, 18, 19]. Moscato et al. [4] studied 44 eyes of 30 patients diagnosed with FNLDO, who underwent SI for a mean duration of 4 (±4.1) months. They were followed for a mean of 2.6 (±2.0) years from the time of intubation. The overall success for resolution of symptoms was seen in 77 %. Extrapolating the data showed success at 50 % between 5 and 6 years. They concluded that SI has good long-term success in cases of FNLDO.

Multiple mechanisms have been postulated to explain the benefit seen with SI in FNLDO [4, 20, 21]. Stent placement increases the volume and hence reduces resistance to outflow. Poiseuille’s law states that resistance to flow is inversely proportional to the fourth power of the radius. Hence, by increasing the diameter of the lumen, the stents reduce resistance to flow (Fig. 14.5). In addition, Moscato et al. [4] proposed the riverbed phenomenon where an increased outflow following reduced resistance helps to maintain the enlarged passage. In addition, the stents may straighten up acute curves impeding outflow as well as help tear outflow by capillary action.

There is good evidence in literature that supports the beneficial effects of DCR in FNLDO patients. Both external DCR (Ex-DCR) and endoscopic DCR (En-DCR) have shown good results. However, these results should be interpreted with caution since few studies did not take into account a strict criteria not to include NLD stenosis, but did demonstrate preoperative patency. The success rates in those with strict criteria ranged from 54 to 84 % [17, 22] and in those without from 50 to 94 % [23–26]. Cho et al. [27] performed a comparative trial between SI (n = 108), En-DCR (n = 32), and Ex-DCR (n = 13) in FNLDO patients. At 6 months’ follow-up, complete resolution of symptoms was achieved in 68.5 % of SI, 81.3 % of En-DCR, and 53.9 % of Ex-DCR. However, these results need to be interpreted with caution because of grossly variable number in each group and variable SI duration and SI confounding effects in DCRs.