idiopathic macular epiretinal membrane ( ierm ) is a relatively common disorder , with an incidence reaching 12% in those older than 70 years .
on one hand , ierm seems to begin with microfractures in the inner retina after posterior vitreous detachment , while , on the other hand , it seems to occur when the external layer of the posterior vitreous cortex remains attached to the macula .
ierm can vary from a single layer to a thick , multilayer fibrocellular proliferation shrinking the retinal surface .
although patients with ierm can be asymptomatic at the beginning , they may complain of various degree of visual symptoms : distortion of lines ( metamorphopsia ) , decreased visual acuity , macropsia , micropsia , and monocular diplopia . in symptomatic patients , the surgical removal of the epiretinal membranes with pars
plana vitrectomy ( ppv ) is the gold standard surgical procedure [ 3 , 4 ] .
, it could be advisable to remove ilm to reduce erm recurrence by eliminating the scaffold for the proliferation of fibrocellular tissue . on the contrary , liu et al .
reported that ilm + erm peeling compared to erm peeling alone , achieved better best - corrected visual acuity ( bcva ) 12 months after surgery but not after 18 months , showing that a longer follow - up would be advisable .
quality of life , contrast , and color sensitivity are becoming useful parameters in the workup of patients affected by ierm , together with visual acuity and retinal morphology .
microperimetry provides information on foveal fixation , macular sensitivity , and depth of central macular defects and is gaining interest in the assessment of various retinal diseases [ 612 ] .
microperimetry , before and after ierm surgery , can help the surgeon in evaluating which kind of patients could benefit from surgery and what could be their prognosis .
moreover , thanks to the autotracking system that corrects involuntary eye movements and the possibility to do follow - up examinations , it allows a greater reliability and reproducibility of the tests than automated perimetry [ 13 , 14 ] .
long - term follow - up is a useful tool to evaluate the effectiveness of a treatment , especially when a total consensus about the timing of a surgical procedure is still not available .
aim of the study was to investigate the potential recovery of retinal functions assessing the microperimetric outcomes in patients affected by ierm and cataract who underwent 25-gauge ppv with ilm peeling combined with phacoemulsification and intraocular lens ( iol ) implantation in a long - term follow - up .
this interventional open label study has been approved by the local institutional ethics committee and review board and registered on clinicaltrials.gov ( number nct01771939 ) .
the research adhered to the tenets of the declaration of helsinki and written informed consent was obtained from all patients before participation in the study . from october 2009 to july 2010 ,
30 eyes of 30 consecutive patients affected by idiopathic epiretinal membranes and various degree of cataract were recruited for the study .
inclusion criteria were ierm clinical finding , macular thickness > 250  m as measured by spectral - domain oct ( sd - oct , rtvue 100 , optovue , fremont , ca ) , presence of metamorphopsia at the amsler grid chart , and a visual acuity loss of 2 snellen lines in the last six months .
exclusion criteria were glaucoma , corneal or lens opacities that precluded an acceptable retinal visualization , ocular axial length > 25  mm ( measured with a - scan biometry ) , epiretinal membrane secondary to trauma or vascular diseases , any macular degeneration , diabetic retinopathy , and/or previous ophthalmic surgery .
all patients underwent a routine ophthalmic examination ( before and at 1 , 7 , 30 , 90 , 180 , and 360 days after surgery ) including slit - lamp biomicroscopy , bcva with the early treatment diabetic retinopathy study ( etdrs ) score at 4 meters , dilated fundus examination , and intraocular pressure measurement using goldmann tonometry .
oct examination calculating central retinal thickness ( crt ) in the central mm using the macular map 5  5  mm ( mm5 ) and microperimetry with the mp1 ( nidek technologies , padova , italy ) were performed before surgery and at 90 , 180 , and 360 days after surgery .
patients were called back to our center four years after the intervention to assess long - term functional and morphological outcomes . an expert vitreoretinal surgeon ( mdv ) performed all surgical procedures . after the insertion of three 25-gauge cannulas , through a 2.75  mm clear - cornea incision , phacoemulsification of the lens was performed . a foldable intraocular lens ( iol ) akreos ao ( bausch and lomb , rochester ,
the core vitrectomy was performed with the accurus machine 25  g+ ( alcon laboratories , fort worth , tx , usa ) .
the posterior hyaloid membrane , if not spontaneously detached , was dyed with micronized triamcinolone acetonide ( ivt , bioos , italy ) , separated by aspiration , and removed .
after the extension of vitrectomy to the ora serrata the membraneblue - dual dye ( dorc , zuidland , netherlands ) was used in order to peel the erm and the ilm within the vascular arcades , with a 25-gauge micro forceps ( alcon laboratories ) .
a second stain with membraneblue - dual dye was applied to check whether the ilm peeling was completed .
an accurate inspection of the peripheral retina and the photocoagulation of eventual retinal holes , tears , or rhegmatogenous degenerations was followed by the exchange of the balanced salt solution ( bss ) with filtered air and cannulas removal .
tobramycin 0.3% and dexamethasone 0.1% eye drops were prescribed 3 times a day for a month after surgery .
patient sat in front of the mp1 with the head carefully aligned in the chin rest and against the forehead strap .
all subjects underwent the exam under dim light conditions with dilated pupil in the study eye .
stimulus size was goldmann iii white spot , with a stimulus duration of 200  ms .
threshold strategy was hfa 4 - 2 , and background luminance was 1.27  cd / m ( 4  asb ) .
stimulus attenuation ranged from 0  db that represents the instrument 's maximum stimulus luminance to 20  db that represents the minimum stimulus luminance .
the automatic eye tracker was used to compensate eye movements and to calculate horizontal and vertical shifts relative to a reference frame during the examination .
the recorded fixation points were classified into three categories for fixation stability analysis ( stable , relatively unstable , and unstable ) .
fixation was regarded as  stable  if more than 75% of the fixation points were inside the 2 diameter circle , as  relatively unstable 
if < 75% were inside the 2 diameter circle but more than 75% inside the 4 diameter circle , and as  unstable  if < 75% were inside the 4 diameter circle .
mean sensitivity ( ms ) , mean defect ( md ) , and the total number of absolute scotoma locations ( points with a threshold value of 0  db ) in the 10 central area were evaluated .
mean retinal sensitivity is the arithmetic mean of all the measured absolute thresholds expressed in db ; mean retinal defect is the arithmetic mean of all local defects , including the values above the upper limits ( expressed in db ) .
secondary outcomes were the changes in bcva , crt , fixation stability at 2 and 4 , and frequency of microscotomas in the 10 area . statistical analysis was carried out with analyse - it statistical software for microsoft excel ( version 2.26 ; analyse - it software , leeds , uk ) .
differences in bcva , crt , and microperimetry values before and after surgery were determined with the wilcoxon signed - ranks tests .
all patients completed the 1-year follow - up visit , whereas 23 of them ( 76.6% ) completed the 4-year follow - up .
7 patients were unable to attend the last follow - up visit : 3 had moved to another city , 2 were unable to come to our center , and 2 of them died . in the 23 patients who completed the 4-year follow - up , no significant differences at all study visits
no significant intraoperative complications were recorded . in one case ( 3.3% ) , a laser photocoagulation was required due to a little iatrogenic hole beyond the vascular arcades , without consequences for the macular function or the visual acuity .
19 patients ( 63% ) developed posterior lens capsule opacity and underwent yag laser capsulotomy before follow - up exams .
preoperative mean visual acuity significantly improved ( p < 0.01 ) after surgery at both 1 and 4 years .
the highest gain in mean visual acuity was documented at 4 years although no significant differences were found between 1 year and 4 years ( p = 0.08 ) .
compared to baseline , at one and 4 years , 16/30 ( 53.3% ) and 15/23 patients ( 65.2% ) presented a gain in visual acuity > 2 etdrs lines , respectively .
mean bcva change was of 3.1 etdrs lines at one year and 3.3 etdrs lines at 4 years .
preoperative mean crt significantly changed ( p < 0.01 ) after surgery at both 1 and 4 years .
baseline mean value was 381.22  69.86  m , while at one and four years 293.71  47.66  m and 280.74  39.57  m were , respectively , measured . in one patient ,
the crt increased ( 31  m at one year and 18  m at 4 years ) probably due to preoperative borderline crt value ( 252  m ) .
no significant changes were observed in mean crt values between 1 and 4 years ( p = 0.08 ) .
significant differences ( p < 0.01 ) were found between preoperative and postoperative data at one and four years for both mean retinal sensitivity and mean defect ( figure 1 ) . at baseline , one year , and four years the mean retinal sensitivity in the 10 central area was 10.48  4.17  db , 12.33  3.66  db , and 14.18  3.46  db , respectively . at baseline , one year , and four years the mean retinal defect in the 10 central area was 9.18  4.40  db , 7.49  3.31  db , and 4.66  2.85  db , respectively .
significant differences were found in ms and md between one and four years after surgery ( p < 0.001 ) .
no significant differences in fixation stability in the central 2 and 4 were found at all visits .
surgical approach in symptomatic patients with ierm showed good results in terms of visual acuity and retinal function recovery with minimal surgical complications and no recurrence of pathology .
the application of dyes during vitreoretinal surgery improved visualization of erm and the vitreoretinal interface .
the toxic effect of dyes used during the peeling can not be excluded . however , trypan blue and brilliant blue g used in this study are recognized safe staining agents with no or minimal toxic effects on retina at the concentrations used .
when patients present a certain degree of cataract , the association of ppv with cataract surgery enables a better visualization of the retina .
moreover , ppv in phakic eyes determines a progression of nuclear sclerosis , and , after vitreoretinal surgery , phacoemulsification is more difficult and with a greater rate of complications [ 16 , 17 ] .
our patients showed a significant and early improvement of functional outcomes and a reduction of crt at oct , as reported in the literature [ 1820 ] .
although after ierm surgery bcva continues to improve up to 2 years , best values are reached at about 1 year , in accordance with our findings , as no changes have been detected between 1 and 4 years [ 2123 ] . as observed by ripandelli et al . in patients who underwent ilm peeling , in our study
the number of microscotomas in the 10 analyzed area improved after surgery , although not significantly . with a steady fixation stability over time , ms and md interestingly increased between 1 and 4 years , demonstrating a significant dissociation between bcva and retinal sensitivity , as has already been demonstrated in other retinal pathologies , underlying the microperimetry capability to detect even subtle changes in patients ' quality of life . as in our study
combined surgery was performed in all cases , it was impossible to determine if the immediate postoperative outcome improvements were completely associated with the ierm removal or with cataract extraction or both .
on the other hand , the double procedure removed an important potential confounding factor in the evaluation of the outcomes after surgery .
this study has some limitations : the small sample size analyzed might have influenced the power of the study , the incomplete follow - up of some patients ( only 67% at four years ) , and the absence of a quantification of metamorphopsia ( e.g. , m - chart ) providing another quality of life parameter .
in conclusion , microperimetry proved an effective diagnostic tool in evaluating subtle changes in retinal function , undetectable with a visual acuity exam .
long - term follow - up after vitreoretinal surgery would be advised to reveal changes in retinal sensitivity affecting patients quality of life . the use of high definition imaging techniques to analyze further aspects of this pathology such as correlation between long - term anatomical changes and microperimetric data are recommended .
 
 purpose . to investigate retinal function using microperimetry in patients affected by idiopathic epiretinal membrane ( ierm ) and 
 cataract who underwent combined surgery : 4-year follow - up . design . 
 prospective , interventional case series . methods . 
 30 eyes of 30 consecutive patients with ierm and age - related cataract underwent 25-gauge vitrectomy and cataract surgery . at baseline , 90 and 180 days , and 1 and 4 years , we examined retinal mean sensitivity ( ms ) , retinal mean defect ( md ) , fixation stability , and frequency of microscotomas using mp1 microperimetry . 
 best - corrected visual acuity ( bcva ) and central retinal thickness ( crt ) using a spectral domain optical coherence tomography ( sd - oct ) were also performed . 
 results . all patients completed 1-year follow - up , while 23 patients reached last follow - up . 
 baseline ms and md ( 10.48  4.17 and 9.18  4.40  db ) significantly changed at one year ( 12.33  3.66 and 7.49  3.31  db , p < 0.01 ) , at four years ( 14.18  3.46 and 4.66  2.85 , p < 0.01 ) , and between one and four years ( p < 0.01 ) after surgery . compared to baseline , crt and bcva significantly changed at one year and remained stable at four years . 
 no variations were observed in fixation stability and frequency of microscotomas compared to baseline . 
 conclusions . 
 long - term follow - up using microperimetry seems useful to evaluate patients after ierm surgery : retinal sensitivity changes even when bcva and crt remain stable . 
1. Introduction
2. Materials and Methods
3. Results
4. Discussion
5. Conclusions