Modern medicine has witnessed evolution and establishment of numerous subspecialties, and dacryology is one such recent addition to the list [1,2,3]. Dacryology is the science of tears and its drainage through the lacrimal system into the nasal cavity. This branch is mostly practiced by ophthalmologists (mainly the oculoplastic surgeons) and otorhinolaryngologists. The chapter focusses on the advances in this newer subspecialty of dacryology over the past few years.

Introduction

The science of dacryology is progressing at a rapid pace taking leaps and bound in both clinical and basic sciences arena across the globe. There is an increasing interest in this subspecialty of ophthalmic plastic surgery and this augurs well for both the science and the patients it deals with. The advances in recent past are numerous [4, 5] and outside the purview of this chapter. The authors however discuss 12 of them in brief, where they have been directly involved in the past 3 years.

Etiopathogenesis of PANDO: The Gender Angle

Primary acquired nasolacrimal duct obstruction (PANDO) is a clinical syndrome and one of its most recognized feature is the female preponderance. Recent qualitative hormonal analyses have shown the presence of numerous hormonal receptors with variable distribution patterns across the lacrimal drainage system [6]. These include estrogen alpha (ERα), estrogen beta (ERβ), aromatase (CYP19), oxytocin (OXTR), progesterone (PGR), testosterone (TSTR), prolactin (PRL), and somatostain receptors 1–5 (Figs. 4.1 and 4.2). Estrogen alpha and beta and aromatase were predominantly epithelial in location, progesterone and testosterone to the basement membranes, stomatostatins to the adluminal vilus surfaces, and oxytocin and prolactin to the cavernous blood vessels and sub mucosal glands, respectively. There were specific patterns and distinctive distribution of receptor expression in healthy males, healthy females and diseased individuals. There is a strong possibility of hormonal micro-environments which are likely to influence the functions and anti-inflammatory milieu in the lacrimal drainage system.

Fig. 4.1
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Immunohistochemistry microphotograph showing high expression of estrogen alpha receptors in the lacrimal drainage epithelia (ERα, ×200)

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Fig. 4.2
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Immunohistochemistry microphotograph showing prolactin receptor expression in the sub mucosal glands of the lacrimal sac (PRL, ×400)

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Ultrastructure of Lacrimal System

Recently, ultrastructural anatomy of lacrimal system has been revisited with scanning electron microscopy (SEM; Fig. 4.3). SEM study of normal adult lacrimal system revealed the presence of distinct features of canalicular valves, specific orbicularis muscle arrangement in the periphery of the canalicular walls and variably rugged external surfaces of the lacrimal system owing to crisscross arrangement of collagen bundles in lacrimal sac and nasolacrimal ducts (NLD) [7]. Presence of dense vascular plexus around lacrimal sac and NLD was noted similar to as shown by Paulsen et al. [8], which facilitates tear outflow via “wrung out” mechanism. No valvular areas were seen in NLD. Reasonably well discernable thickened junctional areas between inner-punctal surface–vertical canaliculus and lacrimal sac–NLD were noted, leading to a speculation about their possible functional roles. The exact role of these areas needs to be studied further, which might help further with etiopathogenesis of NLD obstructions (NLDO).

Fig. 4.3
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Scanning electron microphotograph of the external surface of a punctum

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Etiopathogenesis of Punctal Stenosis

Punctal stenosis is one of the commonly encountered etiologies of epiphora, but its exact pathogenic mechanism is elusive as of now. A step toward unraveling its etiopathogenesis was attempted where immuno-phenotyping and electron microscopy of puncta was performed (Fig. 4.4) [9]. Infiltration of CD45+ and CD3+ T lymphocytes, focal B cell and plasma cell immunoreactivity along with numerous fibroblasts were the significant findings. Electron microscopy showed blunting of epithelial microvilli, abundant fibroblasts, disorderly arranged collagen bundles and mononuclear infiltration in the vicinity of fibroblasts or in between collagen bundles. The presence of specific T lymphocytes in the vicinity of fibroblasts had led to speculation about the possible role of immune cells rather than fibroblasts in triggering the events leading to punctal stenosis.

Fig. 4.4
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Microphotograph showing pathological changes in punctal stenosis (Stain: Masson Trichrome, ×100)

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Lacrimal System Ocular Coherence Tomography

Proximal lacrimal system imaging using Fourier-domain optical coherence tomography (OCT) questioned the long-standing belief that the length of vertical canaliculus is 2 mm long. Maximal visualized depth of vertical canaliculus across published literature on OCT was 1400 μm with an average of 890 μm (Fig. 4.5) [10]. Imaging with spectralis using EDI technology has been found to be of prognostic value in punctal disorders like punctal stenosis, thereby helping in better preoperative counseling [11]. In addition, OCT features of numerous disorders of the proximal lacrimal system like incomplete punctal canalization [12], punctal keratin cyst [13], and canaliculops [14] have been explored recently.

Fig. 4.5
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Ocular coherence tomography image depicting the punctum and the vertical canaliculus

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Mitomycin C

Mitomycin C (MMC) has been used extensively in dacryocystorhinostomy (DCR) surgery; however, the appropriate concentrations and duration have not been standardized. A concentration of 0.2 mg/mL for 3 min was noted to inhibit the proliferation of human nasal mucosal fibroblasts without inducing apoptosis [15] and also correlated with in vitro collagen contractility and wound simulation [16] and hence was considered as an appropriate dose and duration in dacryocystorhinostomy surgeries (Fig. 4.6) [15]. Clinically, wound healing in the postoperative ostium is mediated by several cell types and occurs over a period of 6–8 weeks. Maintenance dose of MMC during healing period can be attained with injectable rather than topical application of MMC. Hence a newer technique of using Circumostial MMC injection in DCR at defined time-points have been proposed, which resulted in anatomical success of 89% in revision DCR (93% after one repeat surgery) and 97% in combined primary DCR and complex cases [17]. These effects were maintained in long-term assessments as well [18]. Transmission electron microscopic studies later confirmed the beneficial effects of both topical and COS MMC on the nasal mucosal healing, hence having implications in healing following dacryocystorhinostomy [19].

Fig. 4.6
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Effect of mitomycin C (MMC) on fibroblast. The image shows the Phalloidin-DAPI merge image of cellular proliferation arrest with the use of MMC

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Lacrimal Stents

The great debate for and against stent usage in DCR surgeries is still unsettled. However, many surgeons agree upon selective intubation for canalicular stenosis, revision DCR, prolong surgeries, poor flaps and post-acute dacryocystitis. Bio-films have recently been studied on the external and luminal surfaces of extubated stents (Fig. 4.7) [20,21,22,23]. Biofilms were noted to be significant beyond 4 weeks of intubation. This combined with the data on postoperative ostium healing [24] suggests that stents, when used in lacrimal surgeries, should ideally not be kept beyond 4 weeks. In addition, extensive deposits and thick mixed biofilms constituted by fungal filaments and bacteria were found within the lumen and this led to a speculation about the possible benefits with the use of non-luminal stents.

Fig. 4.7
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Scanning electron microscopic image of a surface of lacrimal stent showing biofilms

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Image Guided Lacrimal Surgeries

Complex SALDOs with distorted facial anatomy pose a difficult surgical challenge. Stereotactic navigation facilitates safe and precise dacryolocalization in such cases (Fig. 4.8) [25]. Imaging data is acquired preoperatively in the form of 3D CT/MRI and built into the navigation system, which then can be used for radio-anatomic correlation during surgery. Successful outcomes have been demonstrated in all complex cases in one of the series using Stealth navigation system [26, 27]. Newer introductions like telescopes enabled navigation, use of continuously variable viewing telescopes (Endochameleon) have transformed the endoscopic lacrimal surgeries [27, 28].

Fig. 4.8
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Intraoperative image of an infrared navigation guidance

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I-131 and NLDO

The reported frequency of NLDO ranges from 3.4% to 11% following iodine therapy [29]. Radio-uptake studies showed a significant intranasal localization of I-131 in patients receiving dose more than 150 millicurie (mCi) [30]. This could possibly reflect the underlying etiology for bilateral acquired NLDO observed in these cases. Screening of all patients (pre- and post-I-131 therapy), specifically those who receive a dose of more than 150 mCi should be performed. A screening protocol is now in place for patients receiving I-131 along with their risk stratification and clinical assessments [29].

Lacrimal Piezosurgery

The advent of ultrasonic bone emulsification in neurosurgery helped multiple subspecialties to explore this option. Ultrasonic endoscopic DCR has been explored as an alternative modality of managing NLD obstructions [31]. It was found to be safe and effective in both adult and pediatric populations and surgical outcomes were comparable to that of regular powered endoscopic DCRs [32]. In addition, it was also found that the time taken for superior osteotomy with the help of piezo techniques is not significantly different from that of mechanical drills [33]. There is also evidence to suggest that this may be a better modality to use for training in endoscopic DCR as compared to mechanical drills in view of its safety even in the hands of beginners.

Three-Dimensional (3D) Endoscopic Lacrimal Surgeries

The recent development of a 3D enabled 4 mm rigid telescope for nasal surgeries has the potential to revolutionize the way we perform endoscopic lacrimal surgeries (Fig. 4.9). Operating lacrimal surgeries like probing and DCR in 3D planes was found to enhance depth perception, dexterity, and precision compared with the routine 2D intraoperative views [34]. The surgical observers noted enhanced anatomical and surgical understandings in 3D compared with the 2D views [34]. Further detailed comparisons would help formulate guidelines for the routine use of 3D endoscopy in lacrimal surgeries.

Fig. 4.9
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The 3D-ORL Tipcam system for 3D nasal endoscopy

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Quality of Life in Lacrimal Disorders

There is an increasing shift from surgeon-reported outcomes to patient-reported outcomes in lacrimal disorders and quality of life (QOL) assessment is an essential outcome measure. Numerous QOL questionnaires like the Holmes, Glasgow benefit inventory, NLDO-symptom score (NLDO-SS), and lacrimal symptom scores (Lac-Q) are available. The use of Lac-Q is simple and reliable and has specific components addressing the lacrimal symptoms and social symptoms in brief [35]. The usefulness of Lac-Q has been studied in assessing the outcomes of powered endoscopic DCR and monoka stent dilatation for punctal stenosis which appears as a promising tool [36].