THE ROYAL COLLEGE OF OPHTHALMOLOGISTS’ NATIONAL OPHTHALMOLOGY DATABASE STUDY OF VITREORETINAL SURGERY Report 4, Epiretinal Membrane TIMOTHY L. JACKSON, PHD, FRCOPHTH,* PAUL H.J. DONACHIE, MSC,†‡ TOM H. WILLIAMSON, MD, FRCOPHTH,§ JOHN M. SPARROW, DPHIL, FRCOPHTH,†¶ ROBERT L. JOHNSTON, FRCOPHTH†‡ Purpose: To report pragmatic outcomes from a database study of epiretinal membrane surgery. Methods: Prospective anonymized clinical audit data from electronic medical records were pooled over 10 years into a national database, from 1,131 primary epiretinal membrane operations, by 69 surgeons, in 16 U.K. vitreoretinal units. Results: The median age of 1,131 patients was 71.6 years. A pars plana vitrectomy and epiretinal membrane peel were combined with internal limiting membrane peel in 17.0% of operations, and cataract surgery in 49.9%. Use of general anesthesia declined from 94.1% in 2001 to 28.9% in 2010. One or more intraoperative complication occurred in 9.8% (8.1% excluding cataract surgery complications). The median preoperative logarithm of the minimum angle of resolution (logMAR) visual acuity improved from 0.60 to 0.30 (Snellen 20/80–20/40) after a median follow-up of 7.0 months; 41.7% of eyes improved $0.30 logMAR units (approximately 2 Snellen’s lines). The percentages of eyes undergoing subsequent surgery were 3.3%, 1.0%, 0.4%, and 0.8% for epiretinal membrane, retinal detachment, macular hole, and other vitreoretinal indications, respectively. Excluding pseudophakic eyes, 51.7%, 73.2%, and 76.2% of eyes underwent cataract surgery within 1 year, 2 year, and 3 years respectively. Conclusion: These results may help vitreoretinal surgeons to benchmark their surgical outcomes, and patients to assess the risks and benefits of surgery. RETINA 35:1615–1621, 2015
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data collection. There is therefore a risk that results may not be generalizable to standard care, or that publication bias leads to over-reporting of favorable outcomes, if clinicians, and perhaps journals, are reluctant to publish poor outcomes.11 To overcome many of the issues surrounding the reporting of surgical techniques, The Royal College of Ophthalmologists set up the United Kingdom National Ophthalmology Database (NOD). The NOD prospectively collects anonymized surgical data during routine clinical care, using electronic medical records (EMRs), and has so far collected data on more than 380,000 patients, including more than 240,000 cataract operations. By providing representative and generalizable
piretinal membrane (ERM) is a relatively common vitreoretinal disease, with population-based studies suggesting a prevalence of 9.6 per 100 adults, and an annual incidence of 3.2 per 100,000.1 The standard treatment for visually significant ERM is pars plana vitrectomy (PPV) with peeling of the ERM. Surgery is sometimes combined with peeling of the internal limiting membrane,2 the use of vital stains to visualize the ERM or internal limiting membrane,3–8 or cataract surgery.9 Epiretinal membrane is the third most common indication for PPV.10 Most reports of ERM surgery detail a variation in standard surgical technique, and many arise from single centers with relatively small numbers, and retrospective
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data, the NOD aims to help Ophthalmologists compare their surgical outcomes with those of their peers, and to establish national benchmarks. We previously extracted the NOD data relating to all vitreoretinal operations over an 8-year period and presented a pooled analysis of 11,618 vitreoretinal operations.10 We subsequently reported the subset of 1,045 patients undergoing macular hole surgery12 and 3,321 patients undergoing retinal detachment surgery.13 In this report from the NOD, we analyze the data from 1,131 patients undergoing primary ERM surgery. We aim to describe the baseline demographics, surgical techniques, and intraoperative complication rate of primary ERM surgery, and undertake an exploratory analysis of the postoperative change in visual acuity. We also aim to describe the frequency of, and reasons for, further surgery.
Materials and Methods Data Extraction This database study relates to ERM operations performed between February 2001 and November 2010, using data supplied to the NOD. Data were extracted from 13 vitreoretinal units using the same EMR system (Medisoft Ophthalmology; Medisoft Limited, Leeds, United Kingdom) up to November 2010, and from 3 vitreoretinal units using an in-house noncommercial database (VITREOR database, Guy’s and St. Thomas’ NHS Foundation Trust, London, United Kingdom), up to October 2013. The lead clinician and Caldicott Guardian (who oversees data protection) at each hospital gave written approval for the data extraction. Anonymized database analyses of this type do not require ethical permission as they are From the *School of Medicine, King’s College London, London, United Kingdom; †The Royal College of Ophthalmologists, National Ophthalmology Database, London, United Kingdom; ‡Gloucestershire Hospitals NHS Foundation Trust, Cheltenham, United Kingdom; §Guy’s and St. Thomas, NHS Foundation Trust, London, United Kingdom; and ¶Bristol Eye Hospital, Bristol, United Kingdom. Thrombogenics provided an unrestricted grant to fund the initial data analysis. T. L. Jackson is a consultant to Thrombogenics and advisor to Alcon and Bausch & Lomb and DORC. P. H. J. Donachie’s employer received unrestricted funding from Thrombogenics for other related projects. Thrombogenics had no data access, or any input in the study design, data analysis, or article preparation. R. L. Johnston is the Medical Director of Medisoft Limited, which developed the commercial electronic medical record from which data were extracted, for the first iteration of the National Ophthalmology Database (NOD). T. H. Williamson developed the VITREOR database, from which additional vitreoretinal data were extracted to contribute to NOD. J. M. Sparrow has no conflicting interests to disclose. Reprint requests: Timothy L. Jackson, PhD, FRCOphth, Department of Ophthalmology, King’s College Hospital, London SE5 9RS, United Kingdom; e-mail: [email protected]
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viewed as audit or service evaluation.14 This study was conducted in accordance with the declaration of Helsinki, and the U.K.’s Data Protection Act. Surgical Complications The EMRs required surgeons to record whether or not there were any surgical complications, before they could save the operation note. If the surgeon indicated that a complication occurred, then they had to select from a prepopulated list of well-recognized complications specific to that operation, or select “other” and record the complication using free text. All the hospitals using the commercial EMR for vitreoretinal procedures recorded cataract surgery using the same system, with data submitted to the NOD. The centers that used the noncommercial database had a tendency for postvitrectomy cataract operations to be performed in other units, so it was not possible to accurately determine the postvitrectomy rate for these patients. For this reason, only the commercial EMR data were used to estimate the incidence of postvitrectomy cataract surgery (PVCS). Statistical Analysis Surgeon grades were categorized as consultant surgeons, independent nonconsultant surgeons (Staff Grades, Associate Specialists, and Trust doctors), and trainee surgeons (Fellows and Specialist Registrars, Senior House Officers, Specialist Trainees, and Foundation Year doctors). Because of progression through training, an individual surgeon can have data recorded at more than one grade. The time to PVCS was modeled using the Kaplan– Meier method,15 with PVCS modeled as failure. Eyes were censored at the last date on which follow-up data of any type were recorded on the EMR, if they had not had cataract surgery. Visual acuity data were expressed as the logarithm of the minimum angle of resolution (logMAR) with visual acuity categorized as #0.30, .0.30 to 0.60, .0.60 to 0.90, .0.90 to 1.20, and .1.20 at the time of presentation and the last visual acuity measurement record. Visual success was defined as eyes improving by $0.30 logMAR units (approximately 2 Snellen’s lines) from presentation and is reported at 12 and 52 weeks and the last recorded visual acuity measurement (final review). Visual acuity values less than 6 weeks after primary ERM surgery were excluded. We chose to primarily report the median visual acuity as the most appropriate visual acuity outcome, but to allow comparison with the literature, we also reported the mean visual acuity by substituting count fingers (CF), hand motions (HM), perception of light (PL) with 2.1, 2.4, and 2.7, respectively.12,13 Both the median and mean visual acuity were reported at presentation and final
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review. Analysis was conducted using STATA version 11 (StataCorp, College Station, TX). Results Patient Demographics There were 15,667 vitreoretinal operations recorded on the NOD within the study period from 16 participating centers, and of these, 1,226 were for primary ERM treated with PPV and ERM peel. Ninety-five eyes were excluded from the analysis; 22 as these were the second eyes treated for ERM, and 73 as they had previously undergone a vitreoretinal operation in the eye: 54 had a previous retinal detachment surgery, seven previous laser for a retinal tear, and 12 had other vitreoretinal procedures. The 1,131 primary ERM operations were performed on 556 left eyes and 575 right eyes from 1,131 patients, of which 526 (47%) were male, 603 (53%) were female, and the gender was unknown for 2 patients. The median age at the time of primary ERM surgery was 71.6 years (range, 16.1 year–100.1 years). The clinicians using the EMR did not reliably record the duration of symptoms. Surgical Technique and Anesthesia The operations were performed by 69 surgeons. Twenty-seven consultant surgeons performed 709 (62.7%) operations, 12 independent nonconsultant surgeons performed 90 (8.0%) operations, and 37 trainee surgeons performed 332 (29.4%) operations. Seven surgeons performed operations at more than one grade of seniority due to career progression. All operations included PPV and ERM peel, which was combined with an internal limiting membrane peel in 192 (17.0%) and cataract surgery in 564 (49.9%) operations. A tamponade was used in 436 (38.5%) operations: 9 (0.8%) used silicone oil; 116 (10.3%) used sulfahexafluoride (SF6); 100 (8.8%) used hexafluoroethane (C2F6); 36 (3.2%) used perfluoropropane (C3F8); and 175 (15.5%) used air. General anesthesia was used for 457 (40.4%) operations, local anesthesia for 664 (58.7%) operations (21 with sedation), and for 10 (0.9%) operations, the type of anesthesia used was not recorded on the EMR. The rates of general anesthesia fell over the course of the data collection. For example, the rate was 94.1% in 2001 and 28.9% in 2010. Intraoperative Complications Of 1,131 operations, 1,020 (90.2%) were recorded as having no intraoperative complication. Of the 111
(9.8%) eyes having a complication, the most common were iatrogenic retinal tears, iatrogenic retinal trauma, and lens touch (Table 1). Two intraoperative complications occurred in six eyes and three intraoperative complications in two eyes. If the complications associated with cataract surgery were excluded, then the complication rate attributable to ERM surgery alone was 8.1% (90/1,110). Visual Acuity Of the 1,131 eyes in the analysis, 889 (78.6%) had a presenting visual acuity recorded. The median presenting logMAR visual acuity was 0.60 and the mean was 0.66 (20/80 and 20/94 Snellen’s equivalent, respectively). The logMAR visual acuity was #0.30 in 167 eyes, .0.30 to 0.60 in 364 eyes, .0.60 to 0.90 in 208, .0.90 to 1.20 in 98, and .1.20 in 52, including 31 eyes with CF, seven with HM, and two with PL. Table 1. Reported Operative Complications Total (N = 1,131) Operations with no reported complications Operations with one or more reported complications Frequency of specific operative complications Iatrogenic retinal tear Iatrogenic retinal trauma Lens touch Posterior capsular rupture—no vitreous loss* Posterior capsular rupture— vitreous loss* Zonule dialysis* Choroidal/suprachoroidal hemorrhage Corneal edema Retinal hemorrhage Conjunctival buttonhole Corneal epithelial abrasion Infusion cannula in subretinal/ suprachoroidal space Iris trauma* Lens exchange required/other IOL problem* Nuclear/epinuclear fragment into vitreous* Zonule rupture—vitreous loss* Other Total operative complications†
1,020 (90.2%) 111 (9.8%)
55 (4.9) 10 (0.9) 10 (0.9) 8 (0.7) 5 (0.4) 5 (0.4) 3 (0.3) 3 (0.3) 3 (0.3) 3 (0.3) 2 (0.2) 1 (,0.1) 1 (,0.1) 1 (,0.1) 1 (,0.1) 1 (,0.1) 7 (0.6) 119
(%) = column percentage. *Lens-related complications occurring in eyes with combined cataract surgery. †More than one operative complication can be reported for each operation and the sum of the individual complication percentages therefore exceeds the percentage of operations with a complication. IOL, intraocular lens.
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The median presenting logMAR visual acuity in each year of the study ranged from 0.50 to 0.78 and was 0.50 in the each of the last 3 years. Of these 889 eyes, 109 were excluded from the change in visual acuity analysis as there were no further visual acuity measurements, and a further 204 as there were less than 6 weeks follow-up data. Consequently, 576 eyes were available for the change of visual acuity analysis. The median presenting logMAR visual acuity of these eyes was 0.60, with a mean of 0.65 (Snellen 20/80 and 20/91, respectively). At 12 weeks after primary ERM surgery, 219 eyes had a visual acuity record and 71 (32.4%) had achieved visual success ($0.3 logMAR improvement), improving to 39.1% (146/373) at 52 weeks. At 52 weeks, 10.5% (39 eyes) had deteriorated by .0.30 logMAR units. The median and mean presenting visual acuity in the 313 eyes excluded from the change in visual acuity analysis due to absent or short follow-up visual acuity were very similar to the 576 eyes included in the analysis (0.60 and 0.69, respectively). The last recorded visual acuity measurement ranged from 6 weeks to 9.1 years (median, 7.0 months) after primary ERM surgery. At this time, the median visual acuity was 0.30 (Snellen 20/40), the mean visual acuity was 0.47 (Snellen 20/60), and 41.7% (240/576) of eyes had achieved visual success. Fifty-nine (10.2%) eyes lost .0.30 logMAR units from presentation to final review. Of these, 15 had repeat surgery within this time frame, at a median of 6.9 months (range, 0.5 months–29.0 months): eight for ERM, four for retinal detachment,
Fig. 1. The percentage of eyes achieving visual success at 12 weeks (12 weeks), 52 weeks (52 weeks), and final review for 576 eyes with presenting VA, a final review VA and at least 6week follow-up. Visual success was defined as those gaining $0.3 logMAR units (approximately two Snellen’s lines) from presenting logMAR acuity. LogMAR, logarithm of the minimum angle of resolution; VA, visual acuity.
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one for macular hole, and two for other vitreoretinal operations. The worst visual outcomes were CF in 29, HMs in 3, and PL in 3 eyes. More eyes with poorer presenting visual acuity achieved visual success than eyes with a better presenting visual acuity at 12 weeks, 52 weeks, and final review (Figures 1 and 2). The median final review logMAR visual acuity in each year of the study ranged from 0.55 to 0.22 and was #0.30 from the 2005 NHS year onwards. Missing visual acuity data seemed to be due to how the EMRs were used in individual hospitals. Whereas all contributors used the EMR for surgical data capture (with many mandated data fields such as surgical complications), many used paper notes for clinic visits. We compared the median improvement in the 4 units (n = 393 eyes) with the most reliable postoperative visual acuity data capture with the remainder (n = 183). In both groups, the median visual acuity improved by 0.3 log units, from 0.6 to 0.3 at final follow-up. Of the 576 eyes eligible for visual acuity analysis, 315 (54.7%) had combined cataract and vitrectomy ERM surgery, and these eyes had a median logMAR visual acuity of 0.60 at presentation, which improved to 0.30 at final review. Of the 261 (45.3%) eyes that had vitrectomy (not combined with cataract) ERM surgery, the median logMAR visual acuity was 0.50 at presentation and 0.30 at final review. A higher proportion of the combined phakovitrectomy eyes achieved visual success than those that had vitrectomy without cataract surgery (152/315 (48.3%) versus 88/ 261 (33.7%), respectively, P = 0.000).
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Fig. 2. Comparison of the logMAR VA at presentation with the measurement at final review, in 590 eyes. The area of each data point reflects the numbers of eyes in that category. An eye that has an improvement in VA category appears above the diagonal dashed line of identity, eyes with no change in their VA category lie on the line, and eyes with worsening of their VA category lie below the line. The VA improved by at least 1 category in 320 eyes, remained in the same category in 189 eyes, and reduced by at least 1 category in 81 eyes. LogMAR, logarithm of the minimum angle of resolution; VA, visual acuity.
Of the 576 eyes eligible for visual acuity analysis, 67 were known to be pseudophakic at the time of primary ERM surgery. These eyes had a median presenting visual acuity of 0.60 (range, 0.10–CF) that improved to 0.30 (range, 0.00–PL) at final review (from Snellen 20/80–20/40). The chance of visual success was not significantly different to the remainder of the group (Fisher’s exact test, P = 0.693). Further Surgery Of the 1,131 eyes undergoing primary ERM surgery, 928 were excluded from the PVCS analysis:
Fig. 3. A Kaplan–Meier failure graph of postvitrectomy cataract surgery (PVCS), with cataract surgery modeled as failure. The rates are those following primary epiretinal membrane peel surgery, excluding eyes known to be pseudophakic, eyes with lens touch recorded during vitrectomy, or cases with less than 3-week follow-up. The analysis was restricted to data from the centers that used the commercial EMR, and all follow-up times were censored at 5 years as there were no events after 3.5 years.
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247 as they were performed in the centers that did not use the commercial EMR; 104 because they had previously had cataract surgery; 434 as they had combined ERM and cataract surgery; 5 as they experienced a lens touch complication during primary surgery; and 138 as they had less than 3-week followup. Of the remaining 203 eyes eligible for analysis, the median follow-up was 10.1 months (range, 22 days to 5.0 years), and 96 (47.3%) were subsequently recorded as having cataract surgery at some point in time. The 1-, 2-, and 3-year PVCS rates were 51.7%, 73.2%, and 76.2%, respectively (Figure 3). Other subsequent operations, not related to cataract, occurred in 62 eyes: 37 (3.3%) eyes had a repeat ERM operation at a median of 5.5 months (range, 0.2 months–46.6 months) after primary ERM surgery; 11 (1.0%) eyes had retinal detachment surgery at a median of 3.2 months (range, 0.0 months–23.6 months); 5 (0.4%) had macular hole surgery at a median of 3.8 months (range, 3.1 months–12.4 months); and 9 (0.8%) had other types of vitreoretinal surgery at a median of 5.9 months (range, 0.0 months–29.0 months).
Discussion This database study provides anonymized pragmatic data on ERM surgery, including the surgical techniques, intraoperative risks, and the likelihood of postvitrectomy cataract, using data collected from a national database, with an exploratory analysis of visual outcomes. Just less than half the patients underwent cataract surgery at the time of the primary vitrectomy, but if we exclude those known to be pseudophakic before vitrectomy, then this figure rises to 56.5%. Many surgeons advocate combined cataract surgery to speed visual recovery and avoid a second operation to treat postvitrectomy cataract, that would otherwise be required in the majority of cases within 1 year.10 Unexpectedly, a tamponade was used in 38.5% of eyes, most commonly air. The reason for selecting air or gas tamponade is not certain, but may include underreporting of retinal breaks or retinal detachment, the use of gas to encourage closure of self-sealing sclerotomies or resolution of macular fluid, or the creation or coexistence of an unrecorded macular hole. The complications seen in this study are consistent with the literature. Most studies indicate that retinal breaks are the most common intraoperative complication of PPV, with figures varying widely from 0% to 24%.16 Our own database study of 8,257 PPVs undertaken for a range of diseases reported a figure of 3.2%,10 similar to the present ERM subset, but we observed fewer
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retinal breaks with ERM than macular hole (4.9% vs. 6.9%).12 This may be because 79% of eyes with a macular hole have an attached vitreous12 and require induction of a posterior vitreous detachment during surgery, which increases the risk of retinal breaks.17 As with retinal breaks, there is considerable variability in the reported rates of postvitrectomy retinal detachment, with figures ranging from 0% to 16%.16 Ramkissoon reported that new or missed retinal breaks led to retinal detachment in 1.7% of eyes undergoing 20-gauge vitrectomy for a range of diseases, in a large, retrospective, single-center study.17 This is similar to our own figure of 1.0%. Rizzo undertook a large single-center database study of ERM and reported a retinal detachment rate of 1.1%.18 Consistent with our findings, he observed that retinal detachment was less common after ERM surgery than macular hole surgery (1.1% vs. 2.2%, respectively, compared with our figures of 1.0% and 2.4%).12,18 Epiretinal membrane is well known to produce distorted vision and symptoms that are not fully measured by visual acuity charts, and the presence or absence of distortion is not currently extracted to the NOD. Nonetheless, much of the literature reports visual success in terms of the percentage of eyes gaining at least two Snellen’s lines. We therefore selected a logMAR value that is approximately equivalent, to define visual success (eyes gaining $0.30 logMAR units). On this basis, 41.7% of eyes had a successful outcome. Moisseiev surveyed the literature and concluded that approximately 80% of cases gain two or more Snellen’s lines.19 It is well known that publication bias increases the likelihood of reporting favorable results,11 and it is possible that our findings are more generalizable, although our series had a high proportion of cases without visual acuity outcomes recorded. A strength of this large study is that the data were pooled and anonymized and hence may be less subject to publication bias than single-center case series.11 This study was also very inclusive and so results may be more generalizable than randomized controlled trials, which typically have very tight eligibility criteria. Another strength is that surgeons were required to record whether or not there was a complication to save their operation note and to provide the details of any complications that occurred, guaranteeing high levels of operative data completeness. When used live in clinic, the EMR systems also mandate the recording of the presence or absence of postoperative complications, but many sites only use the EMR routinely in the theater setting. It is also not possible to confirm how accurately surgeons recorded intraoperative complications; although their results were anonymized, they may have a natural reluctance to record complications.
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Furthermore, the willingness to record complications may vary across individuals, hospitals, and countries. Another important weakness is that some parameters had more complete data than others. In this respect, the data on surgical techniques and intraoperative complications may be more reliable than data on postvitrectomy cataract and visual acuity outcomes. Incomplete data raise the possibility that data collection was selective, although reassuringly the baseline visual acuity of the eyes excluded due to short or absent visual acuity follow-up data were similar to those included in the visual acuity analysis. Likewise, the centers that reliably used the EMR in both the clinic and theater setting had identical visual acuity outcomes to those that did not. A large database study such as this cannot easily provide detail on the finer points of surgical technique, such as whether or not the ERM and internal limiting membrane were peeled separately or together, or choice and duration of retinal staining. Although it would be possible to mandate these data fields in EMRs, it is important to balance the ease of use in day-to-day practice with a desire to gather key data. In the United Kingdom, most vitreoretinal surgeons undertake cataract surgery, and all the NOD hospitals that used the commercial EMR routinely record cataract surgery using the same EMR, such that even if the patient is referred to other clinicians in the same unit cataract surgery will still be recorded. However, if cataracts were treated elsewhere, then this may lead to underreporting. The same may apply to other late complications. We considered not presenting the visual acuity outcomes as the data had the lowest level of completeness owing to more variable uptake of the EMR in the clinic setting, but conversely this remains one of, if not the largest data set of visual acuity outcomes after ERM surgery. The visual acuity data should however be viewed as exploratory, and interpreted accordingly. Future database studies might consider mandated collection of a nationally agreed set of core benchmark outcomes, as data completeness remains one of the biggest challenges for most database studies. In summary, this study presents the largest, multicentre, clinical database study of ERM surgery to date. The results may help clinicians to benchmark their intraoperative complication rates, patients assess the risks and benefits of surgery, and health care commissioners undertake health economic evaluations. Key words: database study, epiretinal membrane, pars plana vitrectomy, complications, cataract, electronic medical records, United Kingdom, surgery, audit.
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Acknowledgments The authors acknowledge the clinicians who contributed data to The Royal College of Ophthalmologists’ National Ophthalmology Database from the following centers: Airedale NHS Foundation Trust; Bradford Teaching Hospitals NHS Foundation Trust; Calderdale and Huddersfield NHS Foundation Trust; Cambridge University Hospitals NHS Foundation Trust; Gloucestershire Hospitals NHS Foundation Trust; Guys and St. Thomas NHS Foundation Trust; King’s College Hospital NHS Foundation Trust; Leeds Teaching Hospitals NHS Trust; Norfolk and Norwich University Hospitals NHS Foundation Trust; Oxleas NHS Foundation Trust; Peterborough and Stamford Hospitals NHS Foundation Trust; Portsmouth Hospitals NHS Trust; Royal Berkshire NHS Foundation Trust; The London Claremont Clinic; University Hospitals Bristol NHS Foundation Trust; Wirral University Teaching Hospital NHS Foundation Trust. References 1. Simpson AR, Jackson TL. The epidemiology of vitreo-macular interface diseases. In: Aniz Girach, de Smet MD, eds. Diseases of the Vitreo-macular Interface. 1st ed. Berlin: Spinger-Verlag; 2013. 2. Kwok A, Lai TY, Yuen KS. Epiretinal membrane surgery with or without internal limiting membrane peeling. Clin Experiment Ophthalmol 2005;33:379–385. 3. Stanescu-Segall D, Jackson TL. Vital staining with indocyanine green: a review of the clinical and experimental studies relating to safety. Eye (Lond) 2009;23:504–518. 4. Rodrigues EB, Meyer CH, Kroll P. Chromovitrectomy: a new field in vitreoretinal surgery. Graefes Arch Clin Exp Ophthalmol 2005;243:291–293. 5. Feron EJ, Veckeneer M, Parys-Van Ginderdeuren R, et al. Trypan blue staining of epiretinal membranes in proliferative vitreoretinopathy. Arch Ophthalmol 2002;120:141–144.
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6. Perrier M, Sebag M. Epiretinal membrane surgery assisted by trypan blue. Am J Ophthalmol 2003;135:909–911. 7. Enaida H, Hisatomi T, Hata Y, et al. Brilliant blue G selectively stains the internal limiting membrane/brilliant blue G-assisted membrane peeling. Retina 2006;26:631–636. 8. Stalmans P, Parys-Vanginderdeuren R, De Vos R, et al. ICG staining of the inner limiting membrane facilitates its removal during surgery for macular holes and puckers. Bull Soc Belge Ophtalmol 2001;281:21–26. 9. Koenig SB, Mieler WF, Han DP, et al. Combined phacoemulsification, pars plana vitrectomy, and posterior chamber intraocular lens insertion. Arch Ophthalmol 1992;110:1101–1104. 10. Jackson TL, Donachie PH, Sparrow JM, et al. United Kingdom national ophthalmology database study of vitreoretinal surgery: report 1; case mix, complications, and Cataract. Eye (Lond) 2013;27:644–651. 11. Newcombe RG. Towards a reduction in publication bias. Br Med J (Clin Res Ed) 1987;295:656–659. 12. Jackson TL, Donachie PH, Sparrow JM, et al. United Kingdom national ophthalmology database study of vitreoretinal surgery: report 2, macular hole. Ophthalmology 2013;120:629–634. 13. Jackson TL, Donachie PH, Sallam A, et al. United Kingdom National Ophthalmology Database Study of Vitreoretinal Surgery: Report 3, Retinal Detachment. Ophthalmol 2013;121:643–648. 14. National Patient Safety Agency. Defining research. 2010. http://www.hra.nhs.uk/documents/2013/09/defining-research.pdf. 15. Kaplan EL, Meier P. Nonparametric estimation from incomplete observations. J Am Statist Assoc 1958;53:457–481. 16. Dogramaci M, Lee EJ, Williamson TH. The incidence and the risk factors for iatrogenic retinal breaks during pars plana vitrectomy. Eye (Lond) 2012;26:718–722. 17. Ramkissoon YD, Aslam SA, Shah SP, et al. Risk of iatrogenic peripheral retinal breaks in 20-G pars plana vitrectomy. Ophthalmology 2010;117:1825–1830. 18. Rizzo S, Belting C, Genovesi-Ebert F, di Bartolo E. Incidence of retinal detachment after small-incision, sutureless pars plana vitrectomy compared with conventional 20-gauge vitrectomy in macular hole and epiretinal membrane surgery. Retina 2010; 30:1065–1071. 19. Moisseiev E, Davidovitch Z, Kinori M, et al. Vitrectomy for idiopathic epiretinal membrane in elderly patients: surgical outcomes and visual prognosis. Curr Eye Res 2012;37:50–54.
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data collection. There is therefore a risk that results may not be generalizable to standard care, or that publication bias leads to over-reporting of favorable outcomes, if clinicians, and perhaps journals, are reluctant to publish poor outcomes.11 To overcome many of the issues surrounding the reporting of surgical techniques, The Royal College of Ophthalmologists set up the United Kingdom National Ophthalmology Database (NOD). The NOD prospectively collects anonymized surgical data during routine clinical care, using electronic medical records (EMRs), and has so far collected data on more than 380,000 patients, including more than 240,000 cataract operations. By providing representative and generalizable
piretinal membrane (ERM) is a relatively common vitreoretinal disease, with population-based studies suggesting a prevalence of 9.6 per 100 adults, and an annual incidence of 3.2 per 100,000.1 The standard treatment for visually significant ERM is pars plana vitrectomy (PPV) with peeling of the ERM. Surgery is sometimes combined with peeling of the internal limiting membrane,2 the use of vital stains to visualize the ERM or internal limiting membrane,3–8 or cataract surgery.9 Epiretinal membrane is the third most common indication for PPV.10 Most reports of ERM surgery detail a variation in standard surgical technique, and many arise from single centers with relatively small numbers, and retrospective
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data, the NOD aims to help Ophthalmologists compare their surgical outcomes with those of their peers, and to establish national benchmarks. We previously extracted the NOD data relating to all vitreoretinal operations over an 8-year period and presented a pooled analysis of 11,618 vitreoretinal operations.10 We subsequently reported the subset of 1,045 patients undergoing macular hole surgery12 and 3,321 patients undergoing retinal detachment surgery.13 In this report from the NOD, we analyze the data from 1,131 patients undergoing primary ERM surgery. We aim to describe the baseline demographics, surgical techniques, and intraoperative complication rate of primary ERM surgery, and undertake an exploratory analysis of the postoperative change in visual acuity. We also aim to describe the frequency of, and reasons for, further surgery.
Materials and Methods Data Extraction This database study relates to ERM operations performed between February 2001 and November 2010, using data supplied to the NOD. Data were extracted from 13 vitreoretinal units using the same EMR system (Medisoft Ophthalmology; Medisoft Limited, Leeds, United Kingdom) up to November 2010, and from 3 vitreoretinal units using an in-house noncommercial database (VITREOR database, Guy’s and St. Thomas’ NHS Foundation Trust, London, United Kingdom), up to October 2013. The lead clinician and Caldicott Guardian (who oversees data protection) at each hospital gave written approval for the data extraction. Anonymized database analyses of this type do not require ethical permission as they are From the *School of Medicine, King’s College London, London, United Kingdom; †The Royal College of Ophthalmologists, National Ophthalmology Database, London, United Kingdom; ‡Gloucestershire Hospitals NHS Foundation Trust, Cheltenham, United Kingdom; §Guy’s and St. Thomas, NHS Foundation Trust, London, United Kingdom; and ¶Bristol Eye Hospital, Bristol, United Kingdom. Thrombogenics provided an unrestricted grant to fund the initial data analysis. T. L. Jackson is a consultant to Thrombogenics and advisor to Alcon and Bausch & Lomb and DORC. P. H. J. Donachie’s employer received unrestricted funding from Thrombogenics for other related projects. Thrombogenics had no data access, or any input in the study design, data analysis, or article preparation. R. L. Johnston is the Medical Director of Medisoft Limited, which developed the commercial electronic medical record from which data were extracted, for the first iteration of the National Ophthalmology Database (NOD). T. H. Williamson developed the VITREOR database, from which additional vitreoretinal data were extracted to contribute to NOD. J. M. Sparrow has no conflicting interests to disclose. Reprint requests: Timothy L. Jackson, PhD, FRCOphth, Department of Ophthalmology, King’s College Hospital, London SE5 9RS, United Kingdom; e-mail: [email protected]
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viewed as audit or service evaluation.14 This study was conducted in accordance with the declaration of Helsinki, and the U.K.’s Data Protection Act. Surgical Complications The EMRs required surgeons to record whether or not there were any surgical complications, before they could save the operation note. If the surgeon indicated that a complication occurred, then they had to select from a prepopulated list of well-recognized complications specific to that operation, or select “other” and record the complication using free text. All the hospitals using the commercial EMR for vitreoretinal procedures recorded cataract surgery using the same system, with data submitted to the NOD. The centers that used the noncommercial database had a tendency for postvitrectomy cataract operations to be performed in other units, so it was not possible to accurately determine the postvitrectomy rate for these patients. For this reason, only the commercial EMR data were used to estimate the incidence of postvitrectomy cataract surgery (PVCS). Statistical Analysis Surgeon grades were categorized as consultant surgeons, independent nonconsultant surgeons (Staff Grades, Associate Specialists, and Trust doctors), and trainee surgeons (Fellows and Specialist Registrars, Senior House Officers, Specialist Trainees, and Foundation Year doctors). Because of progression through training, an individual surgeon can have data recorded at more than one grade. The time to PVCS was modeled using the Kaplan– Meier method,15 with PVCS modeled as failure. Eyes were censored at the last date on which follow-up data of any type were recorded on the EMR, if they had not had cataract surgery. Visual acuity data were expressed as the logarithm of the minimum angle of resolution (logMAR) with visual acuity categorized as #0.30, .0.30 to 0.60, .0.60 to 0.90, .0.90 to 1.20, and .1.20 at the time of presentation and the last visual acuity measurement record. Visual success was defined as eyes improving by $0.30 logMAR units (approximately 2 Snellen’s lines) from presentation and is reported at 12 and 52 weeks and the last recorded visual acuity measurement (final review). Visual acuity values less than 6 weeks after primary ERM surgery were excluded. We chose to primarily report the median visual acuity as the most appropriate visual acuity outcome, but to allow comparison with the literature, we also reported the mean visual acuity by substituting count fingers (CF), hand motions (HM), perception of light (PL) with 2.1, 2.4, and 2.7, respectively.12,13 Both the median and mean visual acuity were reported at presentation and final
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review. Analysis was conducted using STATA version 11 (StataCorp, College Station, TX). Results Patient Demographics There were 15,667 vitreoretinal operations recorded on the NOD within the study period from 16 participating centers, and of these, 1,226 were for primary ERM treated with PPV and ERM peel. Ninety-five eyes were excluded from the analysis; 22 as these were the second eyes treated for ERM, and 73 as they had previously undergone a vitreoretinal operation in the eye: 54 had a previous retinal detachment surgery, seven previous laser for a retinal tear, and 12 had other vitreoretinal procedures. The 1,131 primary ERM operations were performed on 556 left eyes and 575 right eyes from 1,131 patients, of which 526 (47%) were male, 603 (53%) were female, and the gender was unknown for 2 patients. The median age at the time of primary ERM surgery was 71.6 years (range, 16.1 year–100.1 years). The clinicians using the EMR did not reliably record the duration of symptoms. Surgical Technique and Anesthesia The operations were performed by 69 surgeons. Twenty-seven consultant surgeons performed 709 (62.7%) operations, 12 independent nonconsultant surgeons performed 90 (8.0%) operations, and 37 trainee surgeons performed 332 (29.4%) operations. Seven surgeons performed operations at more than one grade of seniority due to career progression. All operations included PPV and ERM peel, which was combined with an internal limiting membrane peel in 192 (17.0%) and cataract surgery in 564 (49.9%) operations. A tamponade was used in 436 (38.5%) operations: 9 (0.8%) used silicone oil; 116 (10.3%) used sulfahexafluoride (SF6); 100 (8.8%) used hexafluoroethane (C2F6); 36 (3.2%) used perfluoropropane (C3F8); and 175 (15.5%) used air. General anesthesia was used for 457 (40.4%) operations, local anesthesia for 664 (58.7%) operations (21 with sedation), and for 10 (0.9%) operations, the type of anesthesia used was not recorded on the EMR. The rates of general anesthesia fell over the course of the data collection. For example, the rate was 94.1% in 2001 and 28.9% in 2010. Intraoperative Complications Of 1,131 operations, 1,020 (90.2%) were recorded as having no intraoperative complication. Of the 111
(9.8%) eyes having a complication, the most common were iatrogenic retinal tears, iatrogenic retinal trauma, and lens touch (Table 1). Two intraoperative complications occurred in six eyes and three intraoperative complications in two eyes. If the complications associated with cataract surgery were excluded, then the complication rate attributable to ERM surgery alone was 8.1% (90/1,110). Visual Acuity Of the 1,131 eyes in the analysis, 889 (78.6%) had a presenting visual acuity recorded. The median presenting logMAR visual acuity was 0.60 and the mean was 0.66 (20/80 and 20/94 Snellen’s equivalent, respectively). The logMAR visual acuity was #0.30 in 167 eyes, .0.30 to 0.60 in 364 eyes, .0.60 to 0.90 in 208, .0.90 to 1.20 in 98, and .1.20 in 52, including 31 eyes with CF, seven with HM, and two with PL. Table 1. Reported Operative Complications Total (N = 1,131) Operations with no reported complications Operations with one or more reported complications Frequency of specific operative complications Iatrogenic retinal tear Iatrogenic retinal trauma Lens touch Posterior capsular rupture—no vitreous loss* Posterior capsular rupture— vitreous loss* Zonule dialysis* Choroidal/suprachoroidal hemorrhage Corneal edema Retinal hemorrhage Conjunctival buttonhole Corneal epithelial abrasion Infusion cannula in subretinal/ suprachoroidal space Iris trauma* Lens exchange required/other IOL problem* Nuclear/epinuclear fragment into vitreous* Zonule rupture—vitreous loss* Other Total operative complications†
1,020 (90.2%) 111 (9.8%)
55 (4.9) 10 (0.9) 10 (0.9) 8 (0.7) 5 (0.4) 5 (0.4) 3 (0.3) 3 (0.3) 3 (0.3) 3 (0.3) 2 (0.2) 1 (,0.1) 1 (,0.1) 1 (,0.1) 1 (,0.1) 1 (,0.1) 7 (0.6) 119
(%) = column percentage. *Lens-related complications occurring in eyes with combined cataract surgery. †More than one operative complication can be reported for each operation and the sum of the individual complication percentages therefore exceeds the percentage of operations with a complication. IOL, intraocular lens.
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The median presenting logMAR visual acuity in each year of the study ranged from 0.50 to 0.78 and was 0.50 in the each of the last 3 years. Of these 889 eyes, 109 were excluded from the change in visual acuity analysis as there were no further visual acuity measurements, and a further 204 as there were less than 6 weeks follow-up data. Consequently, 576 eyes were available for the change of visual acuity analysis. The median presenting logMAR visual acuity of these eyes was 0.60, with a mean of 0.65 (Snellen 20/80 and 20/91, respectively). At 12 weeks after primary ERM surgery, 219 eyes had a visual acuity record and 71 (32.4%) had achieved visual success ($0.3 logMAR improvement), improving to 39.1% (146/373) at 52 weeks. At 52 weeks, 10.5% (39 eyes) had deteriorated by .0.30 logMAR units. The median and mean presenting visual acuity in the 313 eyes excluded from the change in visual acuity analysis due to absent or short follow-up visual acuity were very similar to the 576 eyes included in the analysis (0.60 and 0.69, respectively). The last recorded visual acuity measurement ranged from 6 weeks to 9.1 years (median, 7.0 months) after primary ERM surgery. At this time, the median visual acuity was 0.30 (Snellen 20/40), the mean visual acuity was 0.47 (Snellen 20/60), and 41.7% (240/576) of eyes had achieved visual success. Fifty-nine (10.2%) eyes lost .0.30 logMAR units from presentation to final review. Of these, 15 had repeat surgery within this time frame, at a median of 6.9 months (range, 0.5 months–29.0 months): eight for ERM, four for retinal detachment,
Fig. 1. The percentage of eyes achieving visual success at 12 weeks (12 weeks), 52 weeks (52 weeks), and final review for 576 eyes with presenting VA, a final review VA and at least 6week follow-up. Visual success was defined as those gaining $0.3 logMAR units (approximately two Snellen’s lines) from presenting logMAR acuity. LogMAR, logarithm of the minimum angle of resolution; VA, visual acuity.
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one for macular hole, and two for other vitreoretinal operations. The worst visual outcomes were CF in 29, HMs in 3, and PL in 3 eyes. More eyes with poorer presenting visual acuity achieved visual success than eyes with a better presenting visual acuity at 12 weeks, 52 weeks, and final review (Figures 1 and 2). The median final review logMAR visual acuity in each year of the study ranged from 0.55 to 0.22 and was #0.30 from the 2005 NHS year onwards. Missing visual acuity data seemed to be due to how the EMRs were used in individual hospitals. Whereas all contributors used the EMR for surgical data capture (with many mandated data fields such as surgical complications), many used paper notes for clinic visits. We compared the median improvement in the 4 units (n = 393 eyes) with the most reliable postoperative visual acuity data capture with the remainder (n = 183). In both groups, the median visual acuity improved by 0.3 log units, from 0.6 to 0.3 at final follow-up. Of the 576 eyes eligible for visual acuity analysis, 315 (54.7%) had combined cataract and vitrectomy ERM surgery, and these eyes had a median logMAR visual acuity of 0.60 at presentation, which improved to 0.30 at final review. Of the 261 (45.3%) eyes that had vitrectomy (not combined with cataract) ERM surgery, the median logMAR visual acuity was 0.50 at presentation and 0.30 at final review. A higher proportion of the combined phakovitrectomy eyes achieved visual success than those that had vitrectomy without cataract surgery (152/315 (48.3%) versus 88/ 261 (33.7%), respectively, P = 0.000).
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Fig. 2. Comparison of the logMAR VA at presentation with the measurement at final review, in 590 eyes. The area of each data point reflects the numbers of eyes in that category. An eye that has an improvement in VA category appears above the diagonal dashed line of identity, eyes with no change in their VA category lie on the line, and eyes with worsening of their VA category lie below the line. The VA improved by at least 1 category in 320 eyes, remained in the same category in 189 eyes, and reduced by at least 1 category in 81 eyes. LogMAR, logarithm of the minimum angle of resolution; VA, visual acuity.
Of the 576 eyes eligible for visual acuity analysis, 67 were known to be pseudophakic at the time of primary ERM surgery. These eyes had a median presenting visual acuity of 0.60 (range, 0.10–CF) that improved to 0.30 (range, 0.00–PL) at final review (from Snellen 20/80–20/40). The chance of visual success was not significantly different to the remainder of the group (Fisher’s exact test, P = 0.693). Further Surgery Of the 1,131 eyes undergoing primary ERM surgery, 928 were excluded from the PVCS analysis:
Fig. 3. A Kaplan–Meier failure graph of postvitrectomy cataract surgery (PVCS), with cataract surgery modeled as failure. The rates are those following primary epiretinal membrane peel surgery, excluding eyes known to be pseudophakic, eyes with lens touch recorded during vitrectomy, or cases with less than 3-week follow-up. The analysis was restricted to data from the centers that used the commercial EMR, and all follow-up times were censored at 5 years as there were no events after 3.5 years.
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247 as they were performed in the centers that did not use the commercial EMR; 104 because they had previously had cataract surgery; 434 as they had combined ERM and cataract surgery; 5 as they experienced a lens touch complication during primary surgery; and 138 as they had less than 3-week followup. Of the remaining 203 eyes eligible for analysis, the median follow-up was 10.1 months (range, 22 days to 5.0 years), and 96 (47.3%) were subsequently recorded as having cataract surgery at some point in time. The 1-, 2-, and 3-year PVCS rates were 51.7%, 73.2%, and 76.2%, respectively (Figure 3). Other subsequent operations, not related to cataract, occurred in 62 eyes: 37 (3.3%) eyes had a repeat ERM operation at a median of 5.5 months (range, 0.2 months–46.6 months) after primary ERM surgery; 11 (1.0%) eyes had retinal detachment surgery at a median of 3.2 months (range, 0.0 months–23.6 months); 5 (0.4%) had macular hole surgery at a median of 3.8 months (range, 3.1 months–12.4 months); and 9 (0.8%) had other types of vitreoretinal surgery at a median of 5.9 months (range, 0.0 months–29.0 months).
Discussion This database study provides anonymized pragmatic data on ERM surgery, including the surgical techniques, intraoperative risks, and the likelihood of postvitrectomy cataract, using data collected from a national database, with an exploratory analysis of visual outcomes. Just less than half the patients underwent cataract surgery at the time of the primary vitrectomy, but if we exclude those known to be pseudophakic before vitrectomy, then this figure rises to 56.5%. Many surgeons advocate combined cataract surgery to speed visual recovery and avoid a second operation to treat postvitrectomy cataract, that would otherwise be required in the majority of cases within 1 year.10 Unexpectedly, a tamponade was used in 38.5% of eyes, most commonly air. The reason for selecting air or gas tamponade is not certain, but may include underreporting of retinal breaks or retinal detachment, the use of gas to encourage closure of self-sealing sclerotomies or resolution of macular fluid, or the creation or coexistence of an unrecorded macular hole. The complications seen in this study are consistent with the literature. Most studies indicate that retinal breaks are the most common intraoperative complication of PPV, with figures varying widely from 0% to 24%.16 Our own database study of 8,257 PPVs undertaken for a range of diseases reported a figure of 3.2%,10 similar to the present ERM subset, but we observed fewer
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retinal breaks with ERM than macular hole (4.9% vs. 6.9%).12 This may be because 79% of eyes with a macular hole have an attached vitreous12 and require induction of a posterior vitreous detachment during surgery, which increases the risk of retinal breaks.17 As with retinal breaks, there is considerable variability in the reported rates of postvitrectomy retinal detachment, with figures ranging from 0% to 16%.16 Ramkissoon reported that new or missed retinal breaks led to retinal detachment in 1.7% of eyes undergoing 20-gauge vitrectomy for a range of diseases, in a large, retrospective, single-center study.17 This is similar to our own figure of 1.0%. Rizzo undertook a large single-center database study of ERM and reported a retinal detachment rate of 1.1%.18 Consistent with our findings, he observed that retinal detachment was less common after ERM surgery than macular hole surgery (1.1% vs. 2.2%, respectively, compared with our figures of 1.0% and 2.4%).12,18 Epiretinal membrane is well known to produce distorted vision and symptoms that are not fully measured by visual acuity charts, and the presence or absence of distortion is not currently extracted to the NOD. Nonetheless, much of the literature reports visual success in terms of the percentage of eyes gaining at least two Snellen’s lines. We therefore selected a logMAR value that is approximately equivalent, to define visual success (eyes gaining $0.30 logMAR units). On this basis, 41.7% of eyes had a successful outcome. Moisseiev surveyed the literature and concluded that approximately 80% of cases gain two or more Snellen’s lines.19 It is well known that publication bias increases the likelihood of reporting favorable results,11 and it is possible that our findings are more generalizable, although our series had a high proportion of cases without visual acuity outcomes recorded. A strength of this large study is that the data were pooled and anonymized and hence may be less subject to publication bias than single-center case series.11 This study was also very inclusive and so results may be more generalizable than randomized controlled trials, which typically have very tight eligibility criteria. Another strength is that surgeons were required to record whether or not there was a complication to save their operation note and to provide the details of any complications that occurred, guaranteeing high levels of operative data completeness. When used live in clinic, the EMR systems also mandate the recording of the presence or absence of postoperative complications, but many sites only use the EMR routinely in the theater setting. It is also not possible to confirm how accurately surgeons recorded intraoperative complications; although their results were anonymized, they may have a natural reluctance to record complications.
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Furthermore, the willingness to record complications may vary across individuals, hospitals, and countries. Another important weakness is that some parameters had more complete data than others. In this respect, the data on surgical techniques and intraoperative complications may be more reliable than data on postvitrectomy cataract and visual acuity outcomes. Incomplete data raise the possibility that data collection was selective, although reassuringly the baseline visual acuity of the eyes excluded due to short or absent visual acuity follow-up data were similar to those included in the visual acuity analysis. Likewise, the centers that reliably used the EMR in both the clinic and theater setting had identical visual acuity outcomes to those that did not. A large database study such as this cannot easily provide detail on the finer points of surgical technique, such as whether or not the ERM and internal limiting membrane were peeled separately or together, or choice and duration of retinal staining. Although it would be possible to mandate these data fields in EMRs, it is important to balance the ease of use in day-to-day practice with a desire to gather key data. In the United Kingdom, most vitreoretinal surgeons undertake cataract surgery, and all the NOD hospitals that used the commercial EMR routinely record cataract surgery using the same EMR, such that even if the patient is referred to other clinicians in the same unit cataract surgery will still be recorded. However, if cataracts were treated elsewhere, then this may lead to underreporting. The same may apply to other late complications. We considered not presenting the visual acuity outcomes as the data had the lowest level of completeness owing to more variable uptake of the EMR in the clinic setting, but conversely this remains one of, if not the largest data set of visual acuity outcomes after ERM surgery. The visual acuity data should however be viewed as exploratory, and interpreted accordingly. Future database studies might consider mandated collection of a nationally agreed set of core benchmark outcomes, as data completeness remains one of the biggest challenges for most database studies. In summary, this study presents the largest, multicentre, clinical database study of ERM surgery to date. The results may help clinicians to benchmark their intraoperative complication rates, patients assess the risks and benefits of surgery, and health care commissioners undertake health economic evaluations. Key words: database study, epiretinal membrane, pars plana vitrectomy, complications, cataract, electronic medical records, United Kingdom, surgery, audit.
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Acknowledgments The authors acknowledge the clinicians who contributed data to The Royal College of Ophthalmologists’ National Ophthalmology Database from the following centers: Airedale NHS Foundation Trust; Bradford Teaching Hospitals NHS Foundation Trust; Calderdale and Huddersfield NHS Foundation Trust; Cambridge University Hospitals NHS Foundation Trust; Gloucestershire Hospitals NHS Foundation Trust; Guys and St. Thomas NHS Foundation Trust; King’s College Hospital NHS Foundation Trust; Leeds Teaching Hospitals NHS Trust; Norfolk and Norwich University Hospitals NHS Foundation Trust; Oxleas NHS Foundation Trust; Peterborough and Stamford Hospitals NHS Foundation Trust; Portsmouth Hospitals NHS Trust; Royal Berkshire NHS Foundation Trust; The London Claremont Clinic; University Hospitals Bristol NHS Foundation Trust; Wirral University Teaching Hospital NHS Foundation Trust. References 1. Simpson AR, Jackson TL. The epidemiology of vitreo-macular interface diseases. In: Aniz Girach, de Smet MD, eds. Diseases of the Vitreo-macular Interface. 1st ed. Berlin: Spinger-Verlag; 2013. 2. Kwok A, Lai TY, Yuen KS. Epiretinal membrane surgery with or without internal limiting membrane peeling. Clin Experiment Ophthalmol 2005;33:379–385. 3. Stanescu-Segall D, Jackson TL. Vital staining with indocyanine green: a review of the clinical and experimental studies relating to safety. Eye (Lond) 2009;23:504–518. 4. Rodrigues EB, Meyer CH, Kroll P. Chromovitrectomy: a new field in vitreoretinal surgery. Graefes Arch Clin Exp Ophthalmol 2005;243:291–293. 5. Feron EJ, Veckeneer M, Parys-Van Ginderdeuren R, et al. Trypan blue staining of epiretinal membranes in proliferative vitreoretinopathy. Arch Ophthalmol 2002;120:141–144.
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6. Perrier M, Sebag M. Epiretinal membrane surgery assisted by trypan blue. Am J Ophthalmol 2003;135:909–911. 7. Enaida H, Hisatomi T, Hata Y, et al. Brilliant blue G selectively stains the internal limiting membrane/brilliant blue G-assisted membrane peeling. Retina 2006;26:631–636. 8. Stalmans P, Parys-Vanginderdeuren R, De Vos R, et al. ICG staining of the inner limiting membrane facilitates its removal during surgery for macular holes and puckers. Bull Soc Belge Ophtalmol 2001;281:21–26. 9. Koenig SB, Mieler WF, Han DP, et al. Combined phacoemulsification, pars plana vitrectomy, and posterior chamber intraocular lens insertion. Arch Ophthalmol 1992;110:1101–1104. 10. Jackson TL, Donachie PH, Sparrow JM, et al. United Kingdom national ophthalmology database study of vitreoretinal surgery: report 1; case mix, complications, and Cataract. Eye (Lond) 2013;27:644–651. 11. Newcombe RG. Towards a reduction in publication bias. Br Med J (Clin Res Ed) 1987;295:656–659. 12. Jackson TL, Donachie PH, Sparrow JM, et al. United Kingdom national ophthalmology database study of vitreoretinal surgery: report 2, macular hole. Ophthalmology 2013;120:629–634. 13. Jackson TL, Donachie PH, Sallam A, et al. United Kingdom National Ophthalmology Database Study of Vitreoretinal Surgery: Report 3, Retinal Detachment. Ophthalmol 2013;121:643–648. 14. National Patient Safety Agency. Defining research. 2010. http://www.hra.nhs.uk/documents/2013/09/defining-research.pdf. 15. Kaplan EL, Meier P. Nonparametric estimation from incomplete observations. J Am Statist Assoc 1958;53:457–481. 16. Dogramaci M, Lee EJ, Williamson TH. The incidence and the risk factors for iatrogenic retinal breaks during pars plana vitrectomy. Eye (Lond) 2012;26:718–722. 17. Ramkissoon YD, Aslam SA, Shah SP, et al. Risk of iatrogenic peripheral retinal breaks in 20-G pars plana vitrectomy. Ophthalmology 2010;117:1825–1830. 18. Rizzo S, Belting C, Genovesi-Ebert F, di Bartolo E. Incidence of retinal detachment after small-incision, sutureless pars plana vitrectomy compared with conventional 20-gauge vitrectomy in macular hole and epiretinal membrane surgery. Retina 2010; 30:1065–1071. 19. Moisseiev E, Davidovitch Z, Kinori M, et al. Vitrectomy for idiopathic epiretinal membrane in elderly patients: surgical outcomes and visual prognosis. Curr Eye Res 2012;37:50–54.
