The location of an ostium should be described in relation to the middle turbinate, which is the most prominent landmark in the vicinity. The most common location of the lacrimal sac is in front of the axilla of middle turbinate (MT) with two-thirds of the sac length above the insertion [23, 24]. Hence, most of the healed ostia should ideally be in front of axilla of MT with some portion above it (Fig. 29.1). Occasionally it may be found behind the axilla of MT or completely above the axilla of MT owing to lacrimal sac’s location (Fig. 29.2).

With a good primary intention healing, majority of the ostia are circular to oval (Figs. 29.1 and 29.3). The more important part of a shape is the depression of the base. The base is depressed but shallow in cases of good mucosa to mucosa approximation all across after a sufficient osteotomy to completely expose the sac (Fig. 29.4). Deep bases are also noted with good mucosal approximation but when the osteotomy is beyond what is sufficient (Fig. 29.3). Although ostia with deep bases are not a problem, the one with shallow bases should be strived for to be as natural as possible. Other shapes like crescentric or vertically narrow are seen in cases of irregular healing and inadequate, patchy cicatrization (Fig. 29.5).

Numerous studies have demonstrated multiple techniques of measuring an ostium (Fig. 29.6) [14–22]. The percentage of reduction from original size subsequently are variable and the reasons are probably multifactorial. However, if mucosa-to-mucosa approximation is achieved all across and the healing completes with primary intention, the reduction in surface area is around 20 % only [23]. Based on the literature and one of the authors’ (PJW) publication and detailed study of ostium, at 4 weeks evaluation, we propose to consider any ostium better than 8 × 5 mm as good (Figs. 29.1 and 29.3) and <4 × 3 mm as a mini-ostium (Fig. 29.7).

Evolution of an ostium in the postoperative period is an important parameter to monitor (Figs. 29.8, 29.9, 29.10, 29.11, and 29.12). It helps in sequentially assessing the healing process and any deviant behaviors that demands intervention. Most of the ostium shrinkage happens in the first 4 weeks and very little if at all beyond that [19, 20]. Regular monitoring helps the surgeon also understand the response to the operative technique and if there is any need to modify step(s) of the surgery. Studying evolution of an ostium would perhaps be partly helpful in determining the benefits or harm of adjunctive procedures in DCR.

Cicatrization is healing of the ostium with a scar tissue. The authors here describe a term, “ostium pseudocicatix,” where the ostium and its parameters are good but much medially toward the septum, there is a vertical thin layer of scar tissue like a curtain (Fig. 29.13). It is important to differentiate this from true cicatrization.

The patient is asymptomatic and functional endoscopic dye test (FEDT) and irrigation are patent. On endoscopy with a 2.7-mm telescope, there is usually a dehiscence, and on visualizing from the edge or through it would make one visualize the normal ostium or FEDT flow (Fig. 29.13). Irregular healing can lead to incomplete cicatrization (Fig. 29.14) or a complete cicatricial closure (Fig. 29.15).

It is important to evaluate any synechiae involving the ostium in the early phases and if found to be directly threatening the tear flow pathway, synechiolysis may be required. Early detection and management prevents consolidation of synechiae. Based on the anatomical location and threat, synechiae can be broadly divided into noninterfering and those interfering or likely to interfere with ostium functions (Fig. 29.16).

The ICO is the junction between the canaliculi and lacrimal sac and represents the distal end of the common canaliculus. The position of the ICO and its dynamicity should be evaluated. The most common location in an ideal ostium is at the base (Fig. 29.3). Occasionally, it is in close relation to one of the four edges (Fig. 29.17) and uncommonly may be hidden by an overhanging edge (Fig. 29.18). ICO can be traced by simple visualization of an opening (Fig. 29.3), its movements, or using a dye test (Fig. 29.17). Beginners can also trace it with the help of silicone tube. While viewing the ICO, the patient is asked to blink and the dynamic movements of ICO are studied with opening and closing of the eyelids. Presence of any obstructive tissues like membranes or rarely granulomas covering the ICO should be noted and appropriate measures like endocanaliculotomy initiated if warranted (Fig. 29.19).

Silicone stents and ostium’s response to their presence should be carefully assessed. After clearing the discharge, the stent should be traceable from its distal cut end right up to the internal common opening (Figs. 29.8, 29.9, 29.10, and 29.11). The dynamicity of the ICO is transmitted to the stents and it is common to observe the tubes moving with each blink. Hence, the stent movements are an indirect indicator of ICO dynamicity. It is important to assess any developing contact granulomas or stent entrapment within healing tissues. Entrapment may rarely occur if the tube is cut very short combined with an aggressive cicatrization.