thirty - eight eyes of 35 glaucoma patients were enrolled in this retrospective cohort study .
the patients were identified from surgical logbooks and clinical databases at department of ophthalmology , uludag university faculty of medicine .
all of the patients had previously undergone viscocanalostomy for primary open - angle glaucoma ( poag ) and secondary open - angle glaucoma ( pseudoexfoliation , pigmentary , and postinflammatory glaucoma ) between 2008 and 2014 .
the eyes with a history of trauma , with previously undergone glaucoma surgery , any eyes suffered from angle closure glaucoma , and insufficient data were excluded from the study .
presurgery data included best - corrected visual acuity , assessed with the snellen chart , goldmann applanation tonometry , slit lamp biomicroscopy , fundoscopy , and gonioscopy .
all the patients had uncontrolled glaucoma that was defined as progressive glaucomatous optic nerve morphology , on maximum tolerated medical therapy .
viscocanalostomy was performed by one surgeon ( author mehmet baykara ) using the method described by stegmann et al . an upper fornix - based conjunctival flap was made .
then , a 5 mm  5 mm , one - third thickness scleral flap was dissected 0.5 mm into the clear cornea . a second square scleral flap , 4 mm  4 mm , two - third thickness , was dissected .
spur , schlemm 's canal was deroofed and peeled its floor . a 30-gauge cannula was used to inject sodium hyaluronate ( 1.4 mg / ml ) , both left and right schlemm 's canal .
the superficial scleral flap was sutured with 10.0 polyglactin sutures , and the conjunctiva was closed with 10.0 polyglactin running sutures .
postoperative laser procedure was performed in cases of higher postoperative intraocular pressures ( iops ) than targeted ( iops equal to or higher than 21 mmhg with or without medications ) .
nineteen of the 38 eyes underwent slt - gr ( 532-nm , frequency - doubled , q - switched , solo lazer ; ellex , adelaide , australia ) ( group 1 ) , and the remaining 19 eyes underwent nd : yag - gp ( conventional 1064-nm , free - running , q - switched , lpulsa syl 9000 ; lightmed , san clemente , ca ) ( group 2 ) . before laser intervention
, all eyes underwent gonioscopic examination and any condition that can lead to complications such as neovascularization , convex peripheral iris configuration was ruled out .
the laser was applied under topical anesthesia , over the surgical area only ( tdm ) , by the same surgeon who carried out the viscocanalostomy ( author mehmet baykara ) . using a glass cgal gonioscopy lens ( haag - streit ag , koeniz , switzerland ) ,
the laser beam was aimed just anterior to the pigmented part of the tdm to avoid iris prolapse .
the conventional nd : yag - gp was conducted with energy levels of 26 mj , spot size of 8 m , and 810 shots ; the modified slt - gr was performed with energy levels of 0.61 mj , spot size of 400 m , and 46 shots .
gonioscopic view of the trabeculo - descemet 's membrane ( surgery area ) and aimed laser spots laser procedures were applied at anterior and lateral edge of the tdm over the surgical area , starting with lower energy levels .
because of high iris incarceration risk , laser goniopuncture was avoided to perform at the center of the tdm with high energy levels , especially during nd : yag - gp . while performing nd : yag - gp , several tiny holes or slit was seen , at slt - gr group champagne bubbles were seen
, there were no visible holes . while sudden drop at iop and bleb formation occurs right after nd : yag - gp , bleb distension happened at the midterm period after slt - gr .
after the laser procedure , examinations included goldmann applanation tonometry , slit lamp biomicroscopy , fundoscopy , and gonioscopy were performed at 1 week , 1 month , 3 months , 6 months , and at 6-month intervals .
the following data were recorded for each subject : sex , age , failure time after viscocanalostomy , iops ( goldmann applanation tonometer ) before and after laser interventions ( 1 week , 1 month , 3 months , 6 months , 1 year , and last visit ) , number of glaucoma medications , complications from the laser procedures , and follow - up periods .
success was defined as maintenance of iop < 20 mmhg for two consecutive visits without increasing prelaser glaucoma medications or 20% decrease from levels before laser procedure .
if the iop failed to drop to target levels , glaucoma medications were added and if the iops higher than 21 mmhg despite the laser procedures and topical antiglaucomatous treatment were defined as surgical failure .
spss 20.0 ( ibm , chicago , usa ) was used to evaluate the results .
all tests were two - tailed , and p < 0.05 was considered statistically significant .
the study was approved by the local ethics committee , according to the tenets of the declaration of helsinki .
patient demographic characteristics mean times between viscocanalostomy and laser procedure were 17.3  9.6 months in group 1 and 14.0  11.4 months in group 2 ( p = 0.096 ) .
iop measurements before laser procedure were 21.2  1.7 mmhg in group 1 and 22.8  1.9 mmhg in group 2 ( p = 0.454 ) .
iop at 1 week after slt - gr was 12.1  3.4 mmhg ; iop at 1 week after conventional nd : yag - gp was 13.6  3.7 mmhg ( p = 0.214 ) .
mean iops at the last visit were 13.8  1.7 mmhg in the slt group at 16.6 months follow - up and 14.9  4.8 mmhg in the conventional nd : yag - gp group at 18.9 months
iop reduction rate after slt - gr at the last visit was 34.9% ; for nd : yag - gp , it was 34.6% . comparing iop values before laser procedures to all follow - up values , the iop - lowering effect was statistically significant in both groups ( p < 0.001 ) .
iop reductions at all follow - up visits were found to be consistent ( p = 0.214 , p = 0.064 , p = 0.242 , p = 0.582 , p = 0.473 and p = 0.703 respectively ) .
intraocular pressure changes after selective laser trabeculoplasty gonioreconditioning and neodymium - doped yttrium - aluminum garnet laser goniopuncture procedures while slt - gr success rate was 100.0% at 6 months , 94.7% at 12 months , nd : yag - gp success rate was 94.7% at 6 months , 89.4% at 12 months .
one eye ( pseudoexfoliation glaucoma ) at slt - gr group and two eyes ( poag ) at nd : yag - gp were identified as a surgical failure despite laser goniopuncture procedures and medical treatment .
while mean number of glaucoma medications was 2.5  1.1 ( range 04 ) before laser intervention and 1.0  0.9 ( range 02 ) at the last follow - up examination ( p < 0.001 ) at slt - gr group , for nd : yag - gp , they were 2.4  1.2 ( range 04 ) and 1.1  0.8 ( range 02 ) , respectively , ( p < 0.001 ) . mean number of glaucoma medications was found to be consistent in both groups at pre- and post - laser periods ( p = 0.892 , p = 0.716 , respectively ) . the only complication that occurred after slt - gr was iris incarceration through the puncture site in one eye .
2 . given that the iop was < 20 mmhg , the subject was observed , and no further interventions were needed . following conventional nd : yag - gp , iris incarceration was determined in three eyes and ocular hypotony was found in two eyes .
iris incarceration occurred acutely after the laser procedure in one eye , and ocular massage and pilocarpine 2% ( pilosed ) drops were successfully applied to treat it . in the other two eyes , iris incarceration presented during the longer follow - up periods , and
iop could not be reduced below the target range by medical therapy alone , and trabeculectomy was performed .
nonpenetrating glaucoma surgery has been increasingly preferred over trabeculectomy in high - risk patients ( uniocular , low vision , high cup / disc ratio , high iop ) due to the lower complication rates .
therefore , the use of postoperative laser procedure has been a trending topic . according to the world glaucoma association guidelines ,
even if it is not needed as an adjunct for all cases , goniopuncture is recommended in cases of increased iop , and it is not defined as postoperative failure . the target of laser goniopuncture is to decrease tdm resistance and lower iop .
conventional nd : yag - gp creates tiny holes or slits using a smaller spot size ( 8 m ) with higher energy power , whereas slt only affects pigmentary tdm cells with a larger spot size ( 400 m ) and less energy per pulse . in the current study ,
we believe that slt may be able to recondition tdm without creating a visible hole , as noted by mansouri et al . in cases
where maintaining the targeted iop can not be achieved after nonpenetrating glaucoma surgery , previous studies in the literature have suggested performing laser goniopuncture before topical antiglaucomatous treatment to prevent fibrosis of the tdm and scleral lake collapse . in a previous study that examined the tdm with in vivo confocal microscopy , laser goniopuncture was not effective after tdm fibrosis .
two previous studies , with 6- and 3-month follow - up periods , reported slt - gr success rates of 90% and 100% , respectively . in the current study , the success rates were 89.4% ( 17/19 ) at 18.9 months follow - up for conventional nd : yag - gp and 94.7% ( 18/19 ) at 16.6 months follow - up for slt - gr .
we believe these variable results depend on creating a proper tdm and the experience of the surgeon performing the laser procedure . in the literature ,
previously reported complications of conventional nd : yag - gp include iris incarceration , hyphema , hypotony , hypotony with maculopathy , late - acute iop rise , choroidal detachment , and blebitis .
higher complication rates occur with nd : yag - gp because the creation of a small hole with high energy levels leads to greater drainage and turbulence .
thus , the higher the iop becomes , the more the complication risk increases . in our study , the iops of one patient with iris incarceration and two patients with postlaser hypotony were > 30 mmhg .
suggested lowering the iop to < 25 mmhg to prevent iris incarceration after laser goniopuncture .
although no complications have been previously reported with slt - gr , one eye in the current study had iris incarceration during long - term follow - up ( 2 months after laser intervention ) .
iris incarceration was a probable result of sudden iop peaks after the laser procedure . to minimize the risk of iris incarceration , anand and pilling suggested that conventional nd : yag - gp should be avoided during the 1 postoperative month when the subconjunctival outflow resistance level is lower .
goniopuncture is best performed on the anterior edge of the tdm , rather than the center , starting with lower energy levels ( 23 mj ) .
prophylactic argon iridoplasty may be an option in case of iris incarceration through the puncture site .
conventional nd : yag - gp and slt - gr are both effective choices on eyes resistant to viscocanalostomy . compared to conventional nd : yag - gp
, slt - gr is a newer procedure , and the rate of complications is lower .
thus , slt - gr can be an alternative to conventional nd : yag - g .
further studies on larger groups with longer follow - up periods would help determine its long - term benefits and complications .
 purpose : to compare the results of conventional 1064 nm neodymium - doped yttrium - aluminum garnet laser goniopuncture ( nd : yag - gp ) and selective 532 nm nd : yag laser ( selective laser trabeculoplasty [ slt ] ) gonioreconditioning ( gr ) on trabeculo - descemet 's membrane in eyes resistant to viscocanalostomy surgery.methods:thirty-eight eyes of 35 patients who underwent laser procedure after successful viscocanalostomy surgery were included in the study . 
 when postoperative intraocular pressure ( iop ) was above the individual target , the eyes were scheduled for laser procedure . 
 nineteen eyes underwent 532 nm slt - gr ( group 1 ) , and the remaining 19 eyes underwent conventional 1064 nm nd : yag - gp ( group 2 ) . 
 iops before and after laser ( 1 week , 1 month , 3 months , 6 months , 1 year , and last visit ) , follow - up periods , number of glaucoma medications , and complications were recorded for both groups.results:mean times from surgery to laser procedures were 17.3  9.6 months in group 1 and 13.0  11.4 months in group 2 . 
 mean iops before laser procedures were 21.2  1.7 mmhg in group 1 and 22.8  1.9 mmhg in group 2 ( p = 0.454 ) . 
 postlaser iop measurements of group 1 were 12.1  3.4 mmhg and 13.8  1.7 mmhg in the 1st week and last visit , respectively ; in group 2 , these measurements were 13.6  3.7 mmhg and 14.9  4.8 mmhg , respectively . 
 there were statistically significant differences ( p < 0.001 ) in iop reduction at all visits in both groups ; the results of the two groups were similar ( p > 0.05 ) . 
 mean follow - up was 16.6  6.4 months after slt - gr and 18.9  11.2 months after nd : yag - gp.conclusions : while conventional nd : yag - gp and slt - gr , a novel procedure , are both effective choices in eyes resistant to viscocanalostomy , there are fewer complications with slt - gr . 
 slt - gr can be an alternative to conventional nd : yag - gp . 
Methods
Results
Discussion
Financial support and sponsorship
Conflicts of interest