Symptomatic and functional effects of N-Acetylcysteine in primary acquired nasolacrimal stenosis

Purpose: To research the effects of N-Acetylcysteine on lacrimation complaint and the opening of the nasolacrimal duct in the cases with primary acquired nasolacrimal duct stenosis (PANS). Materials and methods: A total of 56 patients aged between 16-69 were diagnosed with PANS was started the treatment with NAS four drops per a day. The presence of epiphora and feeling of watering in the nasal passage with nasolacrimal canal (NLC) lavage before drug use was compared after one month of treatment. Results: Twenty-seven (48.21%) of 56 patients had a feeling of nasal watering with lavage. In 32 (57.14%) of the patients, it was found that subjectively watering and epiphora were decreased. Recurrence was observed in 30 of 56 patients (53.57%) at the end of the treatment of 3 months. Conclusion: In the patients with PANS due to mucus plug formation, NAS may provide symptomatic and functional success. It may be considered in the treatment of patients who are not suitable for surgery or who do not want surgery. As a next step, the lavage of NLC with NAS can provide more effective and long-term results. Introduction Primary acquired naso-lacrimal duct stenosis (PANS) is a common cause of epiphora and is thought to be associated with chronic inflammation due to an unknown cause and to be a result of the development of fibrosis causing stenosis. Ocular and periocular diseases such as conjunctival and nasal infections, trauma, sinusitis, toxicity (exposure to trichloramine in pool water) and chronic anti glaucomatous drop treatment, mechanical causes, atopic diseases, and allergic rhino-conjunctivitis may cause secondary nasolacrimal stenosis with inflammation and fibrosis [1-8]. The treatment of PANS is conventional external and endonasal dacryocystorhinostomy and modified surgical procedures with nonendoscopic or mechanical or laser, osteotomy opening of various sizes with mucosal flap, mitomycin-C applied or stent placement. Success rates range from 50% to 100%, and recurrence may occur in some cases [9-22]. N-Acetylcysteine (NAS) is an acetyl derivative of L-cysteine, a natural amino acid, and has mucolytic, antioxidant and corneal collagenase enzyme inhibitor effects. It regulates the production and secretion of mucus by its action on the mucus elasticity/viscosity. Due to its mucolytic and anticholinergic effects, it has been used successfully in dry eye, meibomian gland dysfunction, filamentary keratitis, corneal ulcer, corneal mucous plaque, and alkali corneal burns. In cases of excessive mucus secretion and cases due to filaments, the mucolytic effect occurs when the free sulphydryl (-SH) group in the NAS breaks the disulfide (-S-S-) bridges in mucoprotein molecules of the mucus [22-44]. In the literature, we could not detect the publication regarding the use of NAS in the treatment of PANS. For this reason, we aimed to *Correspondence to: Burak Turgut, Onsekiz Mart University, Faculty of Medicine, Department of Ophthalmology, 17270 Çanakkale, Turkey, E-mail: drburakturgut@yahoo.com


Introduction
Primary acquired naso-lacrimal duct stenosis (PANS) is a common cause of epiphora and is thought to be associated with chronic inflammation due to an unknown cause and to be a result of the development of fibrosis causing stenosis. Ocular and periocular diseases such as conjunctival and nasal infections, trauma, sinusitis, toxicity (exposure to trichloramine in pool water) and chronic anti glaucomatous drop treatment, mechanical causes, atopic diseases, and allergic rhino-conjunctivitis may cause secondary nasolacrimal stenosis with inflammation and fibrosis [1][2][3][4][5][6][7][8].
N-Acetylcysteine (NAS) is an acetyl derivative of L-cysteine, a natural amino acid, and has mucolytic, antioxidant and corneal collagenase enzyme inhibitor effects. It regulates the production and secretion of mucus by its action on the mucus elasticity/viscosity. Due to its mucolytic and anticholinergic effects, it has been used successfully in dry eye, meibomian gland dysfunction, filamentary keratitis, corneal ulcer, corneal mucous plaque, and alkali corneal burns. In cases of excessive mucus secretion and cases due to filaments, the mucolytic effect occurs when the free sulphydryl (-SH) group in the NAS breaks the disulfide (-S-S-) bridges in mucoprotein molecules of the mucus .
In the literature, we could not detect the publication regarding the use of NAS in the treatment of PANS. For this reason, we aimed to evaluate the effects of NAS on irrigation complaints and duct patency in PANS cases which we think that the occlusion is caused by a mucous plug.

Material and methods
56 patients were included in the study, ranging in age from 16-69 and diagnosed as PANS. NAS 4x1 drops started to be applied to eyes with PANS. Nasal and throat examinations were performed before the lavage procedure in order to determine the possible pathologies in the nasal cavity and the lower meatus. The patients who had no nasal pathology and were included in the study. The nasolacrimal duct (NLC) lavage was performed from the lower punctum. Epiphora and NLC lavage and the presence of nasal tearing sensation were compared before the beginning of drug use and after one month of treatment. The study was conducted in accordance with the Helsinki Criteria. Written consent was obtained for the publication of the results of the study and the study.

Results
The mean age of patients was 44,7 years (ranging from 16 to 69 years). Twenty-seven (48.21%) of 56 patients had nasal watering sensation with lavage. In 32 (57.14%) of the patients, it was found that subjectively watering and complain epiphora were decreased.
Recurrence was observed in 30 of 56 patients (53.57%) at the end of the treatment of 3 months.

Discussion
NAS is the acetyl derivative of L-cysteine, a natural amino acid, and it has mucolytic, antioxidant and anticholinergic effects. NAS regulates the production and secretion of mucus by its action on the mucus elasticity/viscosity. The mucolytic effect on the cases of excessive mucus secretion and filaments is caused by the free sulphydryl (-SH) group in the NAS, which breaks down the disulfide (-S-S-) bridges in the mucoprotein molecules of the mucus . In the literature, pressure NAS application in the treatment of NLK obstruction in rabbits has been reported . This is aimed at removing obstruction due to thickened mucus. We have achieved partial success with NAS drop in this case series with no pathology causing secondary stenosis. In our study, the application was not made with pressure lavage but as a drop. This may be a reason for the partial success in our study. We think that the NAS may possibly be due to its anti-inflammatory and mucolytic properties. However, detailed and histopathological studies are needed for the effect of fibrosis.

Conclusion
Although the relapse rate is high, or the treatment is temporary, the NAS may be able to achieve symptomatic and functional success in PANS cases, probably due to a mucus plug formation. In cases where the stenosis is thought to be due to the mucous plug, it may be considered in the treatment if it is not suitable for the operation or does not want the operation.