retinal detachment is the separation of multilayer neurosensory retina from the underlying retinal pigment epithelium . the incidence of rhegmatogenous retinal detachment ( rrd ) has significant geographic variations ranging between 6.3 and 17.9 per 100,000 people per year.1 in current clinical practice , scleral buckling , pars plana vitrectomy ( ppv ) , and pneumatic retinopexy ( pr ) are used to treat rrd2 with reported primary success rates of 95% , 71%92% , and 64% , respectively.3 pr is both safe4 and cost - effective.5 it is used in 14%17% of cases of rrd making it the second most popular primary modality after ppv.6 the classic indications for pr are retinal breaks confined to the superior clock - hours , retinal break or breaks within 12 clock - hours , absence of proliferative retinopathy grade c or d , a cooperative patient who can be positioned , and clear media.7 in addition , in cases with other relative indications , pr was shown to have satisfactory results.7 in spite of the fact that the immediate anatomical success rate of pr has been reported to be lower than that of other techniques , the final best - corrected visual acuity ( bcva ) has been shown to be similar.810 it seems that though the success rate reported by studies investigating pr in the past 3 decades is declining,1012 it remains a popular technique.6 two recent large retrospective studies that investigated the risk factors for failure of pr reported an initial anatomical success rate of 61%63.3% with a final rate of 96.1%99.2%.13,14 the aim of this article was to 1 ) evaluate the initial and final success rate ( both anatomically and functionally ) of pr surgery for primary treatment of rrd ; 2 ) characterize the complications directly related to this procedure ; and 3 ) identify the subset of patients who are most likely to benefit from this procedure as a primary modality . all necessary authorizations were obtained from the institutional review board of the tel aviv medical center . the medical records of patients who underwent pr between the years 2009 and 2012 at the department of ophthalmology of the tel aviv medical center , a tertiary care hospital in tel aviv , israel , were reviewed . in our department , pr is used to repair rrd with retinal breaks located between 8 oclock and 4 oclock . the procedure is not performed in cases with inferior breaks or lattice between the 4 oclock and 8 oclock positions , retinal break > 1 hour , inability to detect retinal breaks in detached retina , clinically significant media opacity preventing identification of breaks , proliferative vitreoretinopathy grade c , previous retinal surgery , or poor patient compliance . patients who underwent ocular surgery ( except cataract surgery ) in the same eye prior to pr were excluded from this study . the demographic and preoperative characteristics extracted from each patient s medical record are depicted in table 1 . all patients were treated with a similar pr technique , adapted from hilton et al by one of the three surgeons ( la , ba , or ss).15 after attempting to identify all the retinal breaks via fundal examination , the necessity , alternatives , and potential complications of the procedure were explained to the patient by the physician before obtaining consent . the pr was performed under retrobulbar or subconjunctival combined with topical anesthesia . in the first stage , afterward , 0.5 ml of sf6 or 0.3 ml of c3f8 was injected into the vitreous . all patients were postoperatively positioned in order to correctly apply pressure to the area of detached retina . single operation success : successful retinal reattachment following a single pr throughout 2 months of follow - up.13 this group included patients who received additional laser or cryotherapy in the postoperative period . additional retinal detachment repair procedures performed in this group were the result of re - detachment occurring after a period of 2 months . final anatomical success : eyes in which the retina remained attached throughout the follow - up period . statistical analyses were performed using spss 21.0 ( ibm corporation , armonk , ny , usa ) . we compared both baseline and follow - up characteristics of primary success patients and failure patients by using , whenever appropriate , student s t - test for normally distributed variables or kruskal we used  or fisher s exact test as indicated for the analysis of categorical variables . we then performed stepwise backward multivariate logistic regression analysis that attempted to determine the baseline variables that enabled to predict success or failure introducing as independent variables those that reached a significant level of < 0.3 in univariate analysis . snellen bcva values were converted to logmar units . a p - value of < 0.05 was considered significant . the medical records of patients who underwent pr between the years 2009 and 2012 at the department of ophthalmology of the tel aviv medical center , a tertiary care hospital in tel aviv , israel , were reviewed . in our department , pr is used to repair rrd with retinal breaks located between 8 oclock and 4 oclock . the procedure is not performed in cases with inferior breaks or lattice between the 4 oclock and 8 oclock positions , retinal break > 1 hour , inability to detect retinal breaks in detached retina , clinically significant media opacity preventing identification of breaks , proliferative vitreoretinopathy grade c , previous retinal surgery , or poor patient compliance . patients who underwent ocular surgery ( except cataract surgery ) in the same eye prior to pr were excluded from this study . the demographic and preoperative characteristics extracted from each patient s medical record are depicted in table 1 . all patients were treated with a similar pr technique , adapted from hilton et al by one of the three surgeons ( la , ba , or ss).15 after attempting to identify all the retinal breaks via fundal examination , the necessity , alternatives , and potential complications of the procedure were explained to the patient by the physician before obtaining consent . the pr was performed under retrobulbar or subconjunctival combined with topical anesthesia . in the first stage , afterward , 0.5 ml of sf6 or 0.3 ml of c3f8 was injected into the vitreous . all patients were postoperatively positioned in order to correctly apply pressure to the area of detached retina . single operation success : successful retinal reattachment following a single pr throughout 2 months of follow - up.13 this group included patients who received additional laser or cryotherapy in the postoperative period . additional retinal detachment repair procedures performed in this group were the result of re - detachment occurring after a period of 2 months . final anatomical success : eyes in which the retina remained attached throughout the follow - up period . statistical analyses were performed using spss 21.0 ( ibm corporation , armonk , ny , usa ) . we compared both baseline and follow - up characteristics of primary success patients and failure patients by using , whenever appropriate , student s t - test for normally distributed variables or kruskal we used  or fisher s exact test as indicated for the analysis of categorical variables . we then performed stepwise backward multivariate logistic regression analysis that attempted to determine the baseline variables that enabled to predict success or failure introducing as independent variables those that reached a significant level of < 0.3 in univariate analysis . snellen bcva values were converted to logmar units . a p - value of < 0.05 was considered significant . out of a total of 102 eyes of 102 patients that underwent pr between the years 2009 and 2012 , 84 patients fulfilled the inclusion criteria . reasons for exclusion were a follow - up period of < 2 months ( n=15 ) and incomplete procedure or lack of data in medical records ( n=3 ) . there were 52 men and 32 women with a mean age of 60.2511.82 years ( median , 60.50 years ; range , 3487 ) who were followed for a mean duration of 11.89.1 months ( median , 9.5 months ; range , 258 months ) . the mean interval between appearance of visual symptoms and patient arrival was 57.9 days ( median , 3 days ; range , 060 days ) . in 56% of the patients , all retinal tears were located in the superior half of the retina , while 61.9% were located specifically in the superotemporal quadrant . retinal tears were limited to 1 hour in 90.5% of the patients , and the size of the retinal detachment was limited to one quadrant or less in 56% of the patients with macular sparing detected in 56% as well . the follow - up time lasted > 3 months in 82% of the patients , > 12 months in 39% , and > 24 months in 9.5% . out of 84 eyes , 50 reached single operation success ( 59.5% ; 95% confidence interval [ ci ] , 48.8170.24 ) , while 82 obtained final anatomical success ( 97.6% ; 95% ci , 94.33100.87 ) . out of the 34 patients from the single operation failure group , 79.4% underwent a single additional reattachment procedure . the mean interval between the primary pr and additional reattachment procedure was 15.4 days ( median , 17 days ; range , 1570 days ) . an overall average of 0.7021.095 additional retinal detachment operations was necessary to achieve final anatomical success . table 1 depicts the clinical characteristics at baseline and after follow - up of the 50 ( 59.5% ) single operation success patients versus the 34 ( 40.5% ) single operation failure patients . briefly , patients from both groups did not differ significantly in any of the variables examined . we used stepwise backward multivariate analysis to determine the effect of the variables that were associated with single operation success at a p - value of < 0.3 ( age , preoperative logmar , time after cataract surgery , and clock - hours detached ) . when examining the subgroup of pseudophakic patients ( n=22 ) , 52.65% of the variation in single operation outcome was explained by the number of clock - hours detached ( partial r=43.76% , p=0.001 ) and to a lesser extent by time after cataract surgery ( partial r=8.89% , p=0.074 ) . table 2 depicts the outcomes of the single operation success group versus the single operation failure group . there was a significant difference between both groups in terms of final bcva ( logmar 0.2290.249 and logmar 0.7470.567 , p<0.001 ) . the difference in delta ( final bcva preoperative bcva ) , however , was not significant ( logmar 0.5440.816 and logmar 0.311.15 , p=0.314 ) . the single operation failure group had higher rates of cataract development and cataract surgery than the single operation success group ( 12.5% vs 30.3% , p=0.048 , and 6.12% vs 48.48% , p<0.001 , respectively ) . the single operation success group required less additional retinal detachment operations to achieve final anatomical success ( 0.20.5 vs 1.41.3 , p<0.001 ) . out of 84 eyes , 50 reached single operation success ( 59.5% ; 95% confidence interval [ ci ] , 48.8170.24 ) , while 82 obtained final anatomical success ( 97.6% ; 95% ci , 94.33100.87 ) . out of the 34 patients from the single operation failure group , 79.4% underwent a single additional reattachment procedure . the mean interval between the primary pr and additional reattachment procedure was 15.4 days ( median , 17 days ; range , 1570 days ) . an overall average of 0.7021.095 additional retinal detachment operations was necessary to achieve final anatomical success . table 1 depicts the clinical characteristics at baseline and after follow - up of the 50 ( 59.5% ) single operation success patients versus the 34 ( 40.5% ) single operation failure patients . briefly , patients from both groups did not differ significantly in any of the variables examined . we used stepwise backward multivariate analysis to determine the effect of the variables that were associated with single operation success at a p - value of < 0.3 ( age , preoperative logmar , time after cataract surgery , and clock - hours detached ) . when examining the subgroup of pseudophakic patients ( n=22 ) , 52.65% of the variation in single operation outcome was explained by the number of clock - hours detached ( partial r=43.76% , p=0.001 ) and to a lesser extent by time after cataract surgery ( partial r=8.89% , p=0.074 ) . table 2 depicts the outcomes of the single operation success group versus the single operation failure group . there was a significant difference between both groups in terms of final bcva ( logmar 0.2290.249 and logmar 0.7470.567 , p<0.001 ) . the difference in delta ( final bcva preoperative bcva ) , however , was not significant ( logmar 0.5440.816 and logmar 0.311.15 , p=0.314 ) . the single operation failure group had higher rates of cataract development and cataract surgery than the single operation success group ( 12.5% vs 30.3% , p=0.048 , and 6.12% vs 48.48% , p<0.001 , respectively ) . the single operation success group required less additional retinal detachment operations to achieve final anatomical success ( 0.20.5 vs 1.41.3 , p<0.001 ) . in this retrospective study , single operation success via pr was achieved in 59.5% of the cases . these rates are consistent with the lower part of the wide spectrum of rates reported in the literature with reported success rates ranging from 44% to 94%.16 the relatively low single operation success rate may be the result of including rrd cases that have , by classic definition , lower primary success rates ( multiple breaks in multiple quadrants ) . vitreous hemorrhage , which coexisted in 11.9% of the rrd cases , may have prevented full identification of all the retinal tears . it is worth mentioning that the nine initial studies between 1986 and 1988 reported single operation success rates that ranged from 84% to 93.55%.16 this is in sharp contrast to the findings of this study and the lower rates reported by three recent studies that demonstrated a range of 60.7%69.6%.13,14,17 no statistically significant differences were found when comparing the baseline characteristics of the single operation success versus single operation failure groups . previous studies have reported substantially higher success rates for phakic rrds in comparison to pseudophakic or aphakic rrds.16 our findings are similar to those of a recent study by fabian et al13 who came to the conclusion that the anatomical outcome is similar in both groups . the main theory for the reported lower success rate is the presence of multiple missed breaks in pseudophakic and aphakic eyes . therefore , before performing pr in pseudophakic rrd , an in - depth examination of the peripheral retina is warranted.15 multivariate analysis of the subgroup of pseudophakic patients revealed that 43.76% of the variation in single operation outcome was explained by the number of clock - hours detached ( r=43.76% , p=0.001 ) . the odds ratio for each clock - hour detached in this group was 3.83 ( 95% ci , 1.0414.12 ) . this in fact means that the size of detachment in pseudophakic patients predicted an increased risk of single operation failure . a study by tornambe et al4 on 302 eyes concluded that more extensive detachments are associated with lower single operation success . we speculate that larger detachments could potentially harbor numerous breaks that are more likely to go undetected in pseudophakic patients . the mean bcva at the final follow - up for single operation success was statistically significantly better for single operation success patients when compared to single operation failure ( logmar 0.2290.249 and logmar 0.7470.567 , p<0.001 , respectively ) . these findings are supported by previous studies that reported better visual outcomes in the single operation success groups.13,14,16 in this study , the difference in delta ( final bcva  preoperative bcva ) between both groups was not statistically significant . we speculate that this may be a result of a relatively low amount of additional retinal detachment procedures required in the single operation failure group ( 1.41.3 ) . these findings are supported by those of ambler et al18 who demonstrated that initial failure of pr does not adversely affect the visual outcome . as there was a substantial difference in the final bcva of both groups , cataract is one of the leading causes of blindness in israel.19 in this study , the single operation failure group had higher rates of cataract development and cataract surgery than the single operation success group ( 12.5% vs 30.3% , p=0.048 , and 6.12% vs 48.48% , p<0.001 , respectively ) . the higher rate of cataract development and cataract surgery in the single operation failure group may have been the result of additional retinal detachment operations performed , such as ppv , which increase the likelihood of developing clinically significant cataract.20,21 therefore , combined surgery by phacoemulsification and vitrectomy in one session may be considered in cases with a significant cataract.22 the retrospective nature of this study in itself is a limitation as there may be several additional factors that were not studied , which may influence the outcomes . as part of the methodology of this study , a relatively large number of parameters that may have affected the outcomes were collected and studied in order to minimize the influence of such factors . in summary , pr as demonstrated in this study carries a lower single operation success rate than initially published 3 decades ago . careful patient selection is warranted before performing pr in rrd , particularly in pseudophakic patients with large detachments . those in which the procedure does not succeed the first time will require on average 1.4 additional procedures to achieve final anatomical success .