posterior vitreous detachment ( pvd ) is defined as the separation of the posterior hyaloid from the internal limiting membrane .
it is age - related and becomes noticeable after the sixth decade of life ( up to 63% prevalence ) and is related to synchysis senilis .
vitreous separation can cause visual symptoms such as photopsia from vitreoretinal traction and floaters resulting from the presence of condensed vitreous collagen .
about 30% of patients have floaters after development of pvd ; however , most patients tolerate their symptoms [ 1 , 2 , 4 ] .
a minority of patients report that these floaters are troublesome , in particular young myopic patients and those whose work requires detailed visual tasks .
pseudophakic patients frequently report floaters , which may be explained by the improved postoperative contrast sensitivity related to the intraocular monofocal lens , which increases the perception of floaters in the visual field [ 2 , 4 ] .
pvd incidence is also increased after cataract surgery by phacoemulsification with implantation of a posterior chamber intraocular lens ( iol ) .
multifocal iols were designed to reduce the need for spectacles by providing two or more points of focus .
the apodized diffractive multifocal acrysof restor iol ( alcon , fort worth , tx ) was designed specifically to reduce glare and halos and provide increased dominant distance vision for patients with large pupils . this lens has a central 3.6  mm apodized optic area with 12 concentric diffractive zones on the anterior surface for gradual reduction of the diffractive increments from the center to the periphery .
rayner m - flex multifocal iols ( rayner , london , uk ) are based on multizoned refractive aspheric optic technology , with either four or five annular zones ( depending on the iol base power [ 7 , 8 ] ) .
the multifocal iol design with concentric rings of optical zones creates positive dysphotopsias , also called photic phenomena .
researchers believe the brain adjusts to the altered visual input over time through neural adaptation . to experience the full visual benefits of multifocal iols , most patients require a neuroadaptation period of about 6 months [ 10 , 11 ] . in the present study , the authors investigated the role of sutureless pars
plana vitrectomy treatment in patients with symptomatic pvd in terms of visual acuity ( va ) and visual satisfaction ( measured through a standardized questionnaire ) in patients who previously underwent bilateral implantation of the restor + 3 ( alcon , fort worth , tx ) or the m - flex iols ( rayner , london , uk ) .
this prospective case series included patients who were not satisfied with their va and complained of halos , glare , and floaters for at least 6 months after having undergone bilateral phacoemulsification using a 2.2  mm microincision technique and implantation of restor + 3 ( alcon , fort worth , tx ) or m - flex iols ( rayner , london , uk ) .
patients underwent a complete preoperative ophthalmologic examination including evaluation of refractive status , measurement of far uncorrected va ( ucva ) and best - corrected va ( bcva ) , slit - lamp examination , goldmann applanation tonometry , and indirect ophthalmoscopy .
ultrasonography , automated visual field measurement using the humphrey 750i visual field analyzer ( zeiss , germany ) , and optical coherence tomography ( oct , spectralis oct , heidelberg , germany ) were also performed , as well as a corneal aberrometry measurement ( galilei dual scheimpflug analyzer , ziemer ophthalmology , switzerland ) . the national eye institute visual function questionnaire 25 ( nei vfq-25 )
all eyes were submitted to yag - laser capsulotomy ( alcon , usa ) at distinct periods after cataract surgery .
patients were informed about the possibility of being submitted to a sutureless ppv surgery to clear media opacities to obtain better focus of the multifocal iol on the retina .
the study protocol was approved by the ethics committees of the federal university of so paulo .
patients were evaluated on postoperative days 1 and 7 and at 1 , 3 , and 6 months postoperatively .
patients were included in the study if they were previously submitted to cataract surgery with multifocal iol implantation and had been diagnosed with symptomatic pvd of at least 6 months of duration .
symptomatic pvd was defined as pvd detected by indirect ophthalmoscopy and fundus biomicroscopy revealing vitreous debris ( which could include a weiss ring but that was not mandatory ) in a patient with pvd - related visual symptoms ( floaters and/or photopsias ) . additionally , ultrasonography had to disclose pvd in the axial , temporal , nasal , inferior , and superior planes
. the refractive error based on objective and subjective dynamic refraction could not exceed 0.25 of spherical and no cylindric refractive errors .
patients also had to have aberrometry showing a root mean square ( rms ) of less than 1.2 in both eyes .
in addition , macular / retinal diseases had to be ruled out by spectral - domain oct , fluorescein angiography , and automated visual fields ( patients excluded if mean deviation values were not between + 1.00 and 7.00 decibels ) .
exclusion criteria were diabetes mellitus , age less than 45 years , a previous stroke or neurosurgical procedure , glaucoma or uveitis , previous ocular surgery other than cataract and multifocal iol implantation , intraoperative complications during a previous phacoemulsification such as capsular tears , previous corneal diseases or scars , irregular corneal astigmatism , iris abnormalities , macular degeneration , neuroophthalmic disease , and postoperative complications such as macular edema and retinal detachment .
four - port ppv using three 23-gauge valved trocars ( dorc , amsterdam , netherlands ) was performed . a tornambe ( synergetics , missouri , usa ) chandelier light pipe connected to a photon ii light source
the surgical procedure was performed using the stellaris pc vitrectomy system ( bausch & lomb , usa ) and a standard 23-gauge vitrectomy probe and the binocular indirect ophthalmomicroscope ( biom ) ( oculus , germany ) for visualization of the vitreous cavity .
a core vitrectomy was performed using 5,000 cuts / minute and an aspiration rate of 200  mmhg for approximately 5 minutes followed by central posterior capsulectomy . in all cases ,
a flush of 0,3  ml of triamcinolone acetonide 4  mg / ml ( ophthalmos , brazil ) was used to confirm the posterior hyaloid removal ; if still present , it was detached by direct aspiration with the vitrectomy probe with a vacuum rate set at 500  mmhg .
scleral indentation was performed and aspiration was reset at 200  mmhg for complete removal of the vitreous base and identification of possible retinal breaks . in bilateral cases ,
the questionnaire of vision quality ( nei vfq-25 ) was applied before and after ppv , in a 1-month interval .
nei vfq-25 includes 25 questions that measure different components of visual function , with six additional optional items that enhance the reliability of the near and distance activity subscales .
these were included in the minimally classic / occult trial of the anti - vegf antibody ranibizumab in the treatment of neovascular amd ( age - related macular degeneration ) study and anti - vegf antibody for the treatment of predominantly classic choroidal neovascularization in amd clinical trial .
the scores ranged from 0 ( worst vision ) to 100 ( best , perfect vision - related function ) .
there are 12 subscales : one general health subscale and 11 vision subscales , including general vision , difficulties related to near and distance vision activities , difficulties related to driving , vision - specific dependency , social functioning , role difficulties , limitations in peripheral and color vision , ocular pain , and mental health issues related to vision .
the overall composite score was calculated using the mean of the subscales , excluding the general health subscale .
a portuguese version of the questionnaire was applied and reliability was assessed using cronbach 's alpha coefficient , intraclass correlation coefficient , and interrater reliability coefficient . to estimate the power of the test ,
we considered simple random sampling and normal distribution for the vfq-25 subscale scores . given these assumptions , the estimated power of the test was between 50 and 90% , depending on the subscale .
the preoperative and postoperative nei vfq-25 scores and ucva using logarithm of the minimum angle of resolution ( logmar ) charts were compared using the nonparametric wilcoxon test .
the analysis was performed using spss software v. 21.0 ( ibm , new york , usa ) .
sixteen eyes of eight patients were included in the analysis and all patients had improvement in ucva after vitrectomy . all studied eyes were submitted to previous yag - laser capsulotomy during the 6-month evaluation before the vitrectomy .
all of the refraction values ranged from 0.25 to + 0.25 diopters with no astigmatism preoperatively and did not change after ppv ; hence , there were no differences between ucva and bcva values .  
table 2 shows the changes in the postoperative vfq-25 scores on its subscales and the comparison between the preoperative and postoperative scores of the vfq-25 .
va significantly improved from a median value of 0.17 preoperatively to 0.09 postoperatively ( p = 0.017 ) ( tables 1 and 2 ) .
all patients with symptomatic pvd confirmed by ultrasonography ( figure 1 ) who underwent ppv reported not only improvement of va but also improvement regarding halos , glare , and floaters ( each of these symptoms was reported preoperatively by all patients ) .
the following postoperative nei vfq-25 subscales median scores significantly improved : general vision ( from 60 preoperatively to 80 postoperatively , p = 0.023 ) , near activities ( from 75 to 92 , p = 0.043 ) , distance activities ( from 67 to 100 , p = 0.041 ) , mental health ( from 75 to 94 , p = 0.011 ) , role difficulties ( from 88 to 100 , p = 0.042 ) , and driving ( from 67 to 92 , p = 0.016 ) ( table 2 and figure 2 ) . at 6-month
follow - up , there were no complications reported ; specifically , no cases of rhegmatogenous retinal detachment and/or macular edema occurred in our series .
vitreous floaters are common symptoms that are classically treated by observation only . floaters may even be considered physiologic and age - related .
however , they can be inconvenient and decrease the va and visual quality of many patients . these symptoms may be exacerbated by multifocal iols , since both pvd and these lenses are known to be responsible for increasing light scattering in ocular media [ 15 , 16 ] .
we hypothesize that symptomatic pvd associated light scattering [ 1 , 18 , 19 ] enhances this phenomenon by diffracting light rays in many directions thus worsening va and quality of vision ( figure 3(a ) ) .
when there are no media opacities ( such as after ppv ) , both near and far light rays can reach the retina at the same point of focus ( figure 3(b ) ) .
it has a well - known risk profile and , justifiably , there is reluctance to perform this surgery to treat floaters .
however , technological advances in both instrumentation and techniques have made ppv a much safer procedure [ 20 , 21 ] .
small - gauge vitrectomy offers the advantages of minimal invasiveness , reduced postoperative inflammation and complications , and faster recovery .
plenty of evidence suggests that quality of life is improved in successfully operated patients [ 2225 ] .
the real issue remains , that is , the safety of this procedure [ 20 , 26 ] .
induction of pvd during surgery is a major risk factor for the development of postoperative rhegmatogenous retinal detachment . in the current small series
, we tried to include only eyes with complete pvd to reduce the risk of retinal detachment .
however , even with preoperative ultrasonographic examination , 12.5% of eyes in our series still required intraoperative induction of pvd .
however , we should remain cautious given the small sample size and the relatively short follow - up .
the authors think that the inclusion of only cases of bilateral disease was coincidental , or there is also the possibility that these patients have more intense symptoms related to pvd .
the results of the current study demonstrate the benefits of ppv in specific eyes with a multifocal iol and symptomatic pvd . a statistically significant ( p = 0.017 ) improvement in ucva ( tables 1 and 2 ) was observed following ppv .
the authors chose to report ucva instead of the most common bcva levels because usually patients with a multifocal iol are expected to have a satisfactory good visual acuity without the need to use glasses or contact lenses ; also , all patients presented no significant refractive error .
all patients reported improvement regarding halos , glare , and floaters . to evaluate quality of vision , we compared the results of the vfq-25 before and after vitrectomy in eyes that underwent previous bilateral multifocal iol implantation ( table 2 ) .
the results showed significantly ( p < 0.05 for all comparisons ) improved postoperative vfq-25 scores in all subscales tested ( near and distance activities , mental health , role difficulty , and driving ) ( table 2 ) .
a comparison between the vfq-25 results in the pre- and postoperative periods at only 1-month interval after vitrectomy was performed in order to avoid the fact that binocular neurosensory adaptation could play a role in vision improvement ; additionally at least 6 months was used as inclusion criteria since the initial symptoms , after the cataract surgery , until the indication of vitreoretinal surgery .
some limitations of the current study must be addressed : first , the small number of patients enrolled , the short follow - up period , and absence of control subjects , since this was a pilot investigation ; second , the lack of contrast sensitivity data , which was not included since the main objective was to observe the response of patients to surgery in terms of visual acuity and quality of life ( as measured by the vfq-25 ) ; third , the inclusion of posterior capsulotomy / capsulectomy in all eyes ( capsulotomy at the preoperative period using the yag - laser and capsulectomy during ppv ) .
additionally , we hypothesized that residual capsular fragments or residual vitreous present at the posterior surface of the multifocal lens could also be related to these symptoms reported .
finally , the explanation of lack of wavefront analysis is based on the argument that we believe the clinical exam , the absence of astigmatism , and also the rms value limit used ( less than 1.2 ) are enough evidences to exclude that possible corneal problems , could be the cause of decrease in quality of vision . despite these , our preliminary results are exciting . to the best of our knowledge ,
this is the first study to address the importance of the posterior vitreous surgery in va and quality of vision in eyes implanted with bilateral multifocal iols .
on the basis of these preliminary data , it is reasonable to conclude that the status of the vitreous is important in patients who may undergo multifocal iol implantation .
preoperative evaluation of candidates for these intraocular lenses implantations should include an assessment of the vitreous .
patients with symptomatic pvd who are not satisfied with their va and quality of vision may benefit from small - gauge ppv in specific situations reported . however , additional clinical trials with large series of patients performed by different surgeons are necessary to confirm these preliminary observations .
 
 purpose . to determine the efficacy of 23-gauge pars plana vitrectomy ( ppv ) for symptomatic posterior vitreous detachment ( pvd ) on visual acuity ( va ) and quality after multifocal intraocular lenses ( iols ) 
 . methods . in this prospective case series , patients who developed symptomatic pvd and were not satisfied with visual quality due to floaters and halos after multifocal iol implantation underwent ppv . examinations included logmar uncorrected visual acuity ( ucva ) , intraocular pressure , biomicroscopy , and indirect ophthalmoscopy at baseline and 1 , 7 , 30 , and 180 days postoperatively . ultrasonography and aberrometry were performed . 
 the visual functioning questionnaire 25 ( vfq-25 ) was administered preoperatively and at 30 days postoperatively . 
 both the postoperative ucva and questionnaire results were compared to preoperative findings using the wilcoxon test . results . 
 sixteen eyes of 8 patients were included . 
 va significantly improved from 0.17 to 0.09 postoperatively ( p = 0.017 ) . 
 all patients reported improvement of halos , glare , and floaters . 
 vfq-25 scores significantly improved in general vision ( p = 0.023 ) , near activities ( p = 0.043 ) , distance activities ( p = 0.041 ) , mental health ( p = 0.011 ) , role difficulties ( p = 0.042 ) , and driving ( p = 0.016 ) . conclusion . 
 ppv may increase ucva and quality of vision in patients with bilateral multifocal iols and symptomatic pvd . 
 larger studies are advised . 
1. Introduction
2. Methods
3. Results
4. Discussion