external or endoscopic dacryocystorhinostomy ( dcr ) is the standard treatment for nasolacrimal duct obstruction ( nldo ) , with or without a previous history of dacryocystitis . the external approach is made through a skin incision near the lacrimal sac and the endoscopic approach is made through the nasal cavity with the aid of a nasal endoscope . the primary benefits of the endoscopic approach are the lack of skin scarring ( there are no skin incisions ) and quicker healing time , and the primary benefits for the external approach are a faster and easier surgery to perform . the surgical success rate was found to correlate with the duration of obstruction and patient 's age ; the surgical success rate was lower when the obstruction lasted longer and the patient was younger . the success rates of the endoscopic approach in nldo are similar to those of the external approach and range between 80% and 96% [ 311 ] . this variability in success rates is likely due to differences in surgical techniques , patient demographics , and lack of standardized outcome measures . only a few earlier studies examined the effect of past dacryocystitis on the success rates of external dcr . the success rates in those studies were lower than studies who examined dcr without dacryocystitis . their reported success rates range from 69% to 88% [ 12 , 13 ] . according to our clinical experience , the success rates of dcr for patients with and without previous episodes of chronic or acute dacryocystitis should be similar . our current study presents a series of patients with or without previous episodes of dacryocystitis who underwent external dcr for nldo and compares their preoperative characteristics , postoperative outcomes , and surgical success rates . institutional review board ( irb ) approval for conducting this study was granted by the tel aviv sourasky medical center . we retrospectively reviewed the medical files of all patients who were referred to our tertiary referral center and underwent external dcr between 2006 and 2011 . the patients were divided into two groups : patients with and without previous episodes of chronic or acute dacryocystitis ( as determined by physical examination ) . acute dacryocystitis was defined by the appearance of pain , erythema , or pus discharge and swelling of the lacrimal sac . chronic dacryocystitis was defined by the appearance of epiphora and purulent discharge from the punctum . in the presence of dacryocystitis , the pus was drained and antibiotic treatment with oral amoxicillin and clavulanate ( 875  mg  2/d ) was started . only after resolution of the acute phase , an external dcr was performed . in some cases , if the main complaint was epiphora , lacrimal syringing was performed followed by external dcr in patients with nldo . the extracted data included patients ' demographics , indication for surgery , background diseases ( systemic and ocular ) , duration of epiphora , side of obstruction , previous external dcr , early and late postoperative complications , duration of the stenting tube , and surgical outcome . they all underwent external dcr and had a complete postoperative followup of at least 6 months . excluded were patients who underwent endoscopic dcr , those with a functional obstruction , those aged less than 16 years , and those with inadequate followup . success was determined by postoperative patency on syringing and resolution of epiphora at 6 months after surgery . we use a standard technique based on a straight incision made medial to the angular vein at the level of the medial canthal ligament . an osteotomy of 1.52  1.52  cm was created , and the lacrimal sac and mucosa were opened to form anterior and posterior flaps . a silicon tube ( bica , 2012 fci ophthalmics , marshfield hills , ma ) was inserted and tied , after which the anterior and posterior flaps are sutured with 6/0 vicryl sutures . the wound is closed with absorbable sutures ( 5/0 vicryl rapide or 6/0 coated vicryl ) . all patients were treated postoperatively with topical maxitrol ( dexamethasone , polymyxin b sulphate , and neomycin sulphate ) ointment on the skin incision and ofloxacin eye drops 3 times a day for 710 days . if dacryocystitis was evident during the surgery ( pus in the lacrimal sac ) , treatment with oral amoxicillin and clavulanate ( 875  mg  2/d ) for 5 days was added . the removal of the silicone tube took place only when there was a patency on syringing and resolution of epiphora and at least 6 weeks passed from the surgery . fisher 's exact test and  analysis were used for comparison between categorical variables , and a t - test was used for comparing continuous variables . for multivariate analyses , a logistic regression was used to calculate the odds ratio ( or ) which was used to predict the odds of developing dacryocystitis in the presence of glaucoma or past cataract surgery . during the study period , 185 patients underwent external dcr and 152 of them met the inclusion criteria . the participants included 100 females and 52 males ( mean age 67  15 years ) , of whom 60 were diagnosed with dacryocystitis ( acute or chronic ) and 92 were not . the mean duration of epiphora prior to the first admission to the clinic was 33 months for patients without dacryocystitis and 28 months for patients with a previous episode of dacryocystitis ( p = 0.001 ) . there was no difference in the percentage of laterality of the obstruction in the former group ( 27 ( 29.3% ) right , 29 ( 31.5% ) left , and 36 ( 39.1% ) bilateral ) . in contrast , significantly fewer patients with a previous episode of dacryocystitis had bilateral obstruction ( 12 ( 20% ) , p = 0.028 ) , and significantly more of them had a left - side obstruction ( 29 ( 48.3% ) , p = 0.031 ) compared to the patients without dacryocystitis ( table 1 ) . there was no significant association between hypertension , ischemic heart disease , hyperlipidemia , diabetes , hyperthyroidism , and anemia and the occurrence of dacryocystitis . two ( 2.2% ) of the 92 patients without a previous episode of dacryocystitis were diagnosed with glaucoma , compared to 10 ( 16.7% ) of the 60 patients with dacryocystitis ( p = 0.002 ) . the presence of glaucoma with epiphora duration of less than 11.5 months was significantly predictive of the development of dacryocystitis ( p = 0.019 ) ; the odds were 6.71 times greater than those for nonglaucomatous patients . fourteen patients without dacryocystitis ( 15.2% ) and 17 patients with a previous episode of dacryocystitis ( 28.3% ) underwent cataract surgery in the past , and they had a tendency to develop dacryocystitis in the presence of nldo ( p = 0.064 ) ( table 2 ) . the mean postoperative follow - up time was 19 months for patients without dacryocystitis and 20 months for patients with a previous episode of dacryocystitis ( p = 0.783 ) . it occurred in 6 patients without dacryocystitis ( 6.5% ) and in 6 patients with a previous episode of dacryocystitis ( 10% ) ( p = 0.542 ) . the silicone tube was removed after a mean duration of 86 days in patients without dacryocystitis and after a mean duration of 79 days in patients with a previous episode of dacryocystitis ( p = 0.333 ) . after a minimal period of 6 months , patency on syringing and resolution of epiphora was documented in 80 patients without dacryocystitis ( 86.7% ) and in 56 patients with previous episode of dacryocystitis ( 94.4% ) ( p = 0.337 ) . our comparisons of patients ' characteristics and surgical outcome results of external dcr in patients with nldo , with and without a past history of dacryocystitis , revealed no significant differences between the two groups . in the literature , the reported surgical success rates of external dcr in patients with no prior episodes of dacryocystitis ranged from 80% to 96% [ 311 ] . only a few earlier studies examined the effect of past dacryocystitis on the success rates of external dcr and reported them as being lower than in cases without dacryocystitis . follow - up assessments of 662 patients with chronic dacryocystitis who underwent external dcr included symptom evaluation and irrigation of the lacrimal passage . surgical success was defined by being asymptomatic and having patent lacrimal passages , and it was achieved in 88.6% of their patients . successful outcomes were defined as diminished epiphora or no observable reflux from the canaliculus during or after lacrimal irrigation . the patients of both studies were followed up at 1 , 3 , and 6 months and one year after surgery . additional predictive factors for lower external dcr success rates are the duration of obstruction and patient 's age . noted that lower success rates are common in younger patients compared to older ones , while early operations offer greater success . .   found that patients who had longer - lasting symptoms of chronic dacryocystitis had lower success rates . we found that , in patients with previous episodes of dacryocystitis , the obstruction was more common on the left side . a suggested explanation is that the angle formed between the left nasolacrimal sac and duct is smaller than that on the right side , and this allows proliferation of bacteria [ 14 , 15 ] . we found that a shorter mean duration of epiphora ( equivalent to a shorter duration of nldo ) correlated with previous episodes of dacryocystitis and that there was no difference in the surgical success rates in these patients . we believe that the reason for similar surgical results in both groups is a shorter duration of epiphora in patients with dacryocystitis . our results revealed that patients with glaucoma have higher odds ( 6.71-fold ) to develop dacryocystitis in the presence of nldo compared to patients without glaucoma . to the best of our knowledge , neither a direct correlation between glaucoma and nldo nor between glaucoma and dacryocystitis has been reported previously . there are , however , a few reports on antihypertensive medications as a cause of nldo or lacrimal canalicular obstruction . reported that chronic use of timolol - containing topical glaucoma therapy preparations in glaucoma patients is associated with an increased risk of developing nldo . mcnab [ 17 , 18 ] demonstrated that the punctum and canaliculus are the main anatomical sites of lacrimal drainage system obstruction associated with topical antihypertensive medications . although topical glaucoma therapy can cause nldo , we found no reports on a correlation between glaucoma / antihypertensive medications and dacryocystitis , nor any correlation between nldo caused by topical antihypertensive medications and the occurrence of dacryocystitis . the correlation we observed between past cataract surgery and nldo with dacryocystitis did not reach a level of significance ( p = 0.064 ) . we did not find any studies in the literature on such an association . according to our findings , patients with glaucoma or past cataract surgery who have nldo are prone to develop dacryocystitis . we therefore suggest that these patients be warned about this complication and instructed to seek medical treatment at the first occurrence of epiphora . in addition , the information on the patients ' diseases was taken from their medical charts , and the duration of epiphora was self - reported by the patients . in conclusion , we found no significant difference in the success rates of external dcr in patients with or without a previous episode of dacryocystitis . our finding that patients with glaucoma and nldo have a higher risk of developing dacryocystitis should be confirmed in larger - scale studies .