Endophthalmitis after Pars Plana Vitrectomy

A 20- and 25-Gauge Comparison

Allen Y. H. Hu, MD,1 Jean-Louis Bourges, MD,1,2 Sumit P. Shah, MD,1 Anurag Gupta, MD,1

Christine R. Gonzales, MD,1 Scott C. N. Oliver, MD,1 Steven D. Schwartz, MD1

Objective: Recent retrospective analyses have suggested that postoperative endophthalmitis may be morefrequent with 25- than 20-gauge pars plana vitrectomy (PPV). Because the infection risk may depend on thesuturing status of the sclerotomy, and the perioperative anti-infection protocol, we compared the incidence rateof endophthalmitis after sutureless 25-gauge versus sutured 20-gauge PPV on a large cohort of patientsoperated with a standardized perioperative anti-infection protocol.

Design: Retrospective comparative case series.Participants: Consecutive patients who underwent 20- or 25-gauge PPVs at a single center over a multi-

year period.Methods: We analyzed 3597 consecutive PPVs. Patients with a pre-PPV diagnosis of endophthalmitis, PPVs

performed for implantation of drug delivery devices, or 25-gauge PPVs with all sclerotomies sutured closed wereexcluded. Patients with �1 week of follow-up were divided into 2 study groups by sclerotomy status at the endof surgery: the 20-gauge group had 3 sutured 20-gauge sclerotomies, and the 25-gauge group had �1 unsutured25-gauge sclerotomy. Endophthalmitis was defined by clinical criteria independent of microbiological results.

Main Outcome Measures: The incidence of endophthalmitis was compared between 25- versus 20-gaugegroups.

Results: Of 3372 PPV surgeries meeting inclusion and exclusion criteria, 1948 and 1424 surgeries were 20-and 25-gauge PPVs, respectively. Average age (� standard deviation) of patients was 54.6 (� 22.6) and 64.4 (�16.5) years in the 20- and 25-gauge PPV groups, respectively (P�0.0001). Median post-PPV follow-up time wasnot significantly different between the 2 groups (12.5 vs 13.0 months; P � 0.69). Endophthalmitis was observedin 1 patient (0.07%; 95% confidence interval, 0%–0.21%) from the 25-gauge group and none in the 20-gaugegroup (P � 0.42; Fisher exact test, 2-tailed). The use of air/gas endotamponade (P�0.0001) and intravitrealtriamcinolone (P�0.001) was more common in 25- versus 20-gauge PPV.

Conclusions: The incidence of endophthalmitis was low in both groups. We were unable to show asignificant difference in the incidence of endophthalmitis between sutureless 25-gauge and sutured 20-gaugePPV, and conclude that a careful perioperative anti-infection protocol may reduce 25-gauge PPV endophthalmi-tis risk to that of 20-gauge PPV.

Financial Disclosure(s): Proprietary or commercial disclosure may be found after the references.

Ophthalmology 2009;116:1360–1365 © 2009 by the American Academy of Ophthalmology.

Rates of endophthalmitis after conventional pars plana vit-rectomy (PPV) have decreased over the past 20 years. Hoand Tolentino1 reported an endophthalmitis rate as high as0.15% after PPV in 1984. In subsequent years, rates re-ported from the mid-1980s to early 2000s have decreased,ranging from 0.03% to 0.05%.2–6

Recent advances in retinal surgery techniques and instru-mentation, such as 25-gauge PPV, have permitted use ofsutureless vitrectomy through small, self-sealing, transcon-junctival wounds, which allow patients to recover morequickly and comfortably. These and other perceived advan-tages have led surgeons to expand the indications for andincrease use of 25-gauge sutureless PPV.7–13

Despite these advantages, concerns have been raisedabout the lack of high-level clinical trials based evidencedemonstrating safety and efficacy.14 Postoperative endoph-

thalmitis after 25-gauge vitrectomy was first reported in

1360 © 2009 by the American Academy of OphthalmologyPublished by Elsevier Inc.

2005, followed by other reports in 2006 through 2008.15–19

Some studies have suggested that the postoperative endoph-thalmitis rate is higher with 25- than 20-gauge PPV. In asingle-center comparison of 20-gauge sutured vitrectomyversus 25-gauge sutureless vitrectomy, Kunimoto et al16

reported a 12-fold higher incidence of endophthalmitis with25- versus 20-gauge surgery. More recently, in a study ofpooled data from multiple surgeons at 7 centers, Scott et al17

reported a 28-fold higher rate of endophthalmitis with 25-versus 20-gauge.

Proposed hypotheses explaining why sutureless transcon-junctival 25-gauge PPV may lead to a higher rate of postop-erative endophthalmitis vary. Some theories relate to a lack ofcomplete wound closure.20 Unsutured wounds may lead toearly postoperative hypotony in 0% to 30% of 25-gauge cases,allowing an intraocular influx of extraocular fluid and micro-

organisms.8,10–13,21 (Gupta et al IOVS 2003, v 44). Others

ISSN 0161-6420/09/$–see front matterdoi:10.1016/j.ophtha.2009.01.045

s wick

Hu et al � Endophthalmitis after Vitrectomy

propose that lower infusion rates are a feature of 25-gaugevitrectomy, and the reduced influx and efflux of fluid mayallow a greater bacterial inoculum to remain in the eye.9

Still others postulate that less vitreous gel is removed duringa 25- versus 20-gauge PPV and that this residual vitreousskirt may facilitate bacterial adherence and sequester bac-teria from normal immunologic factors and extraocular an-tibiotics.22 Finally, prolapse of a vitreous wick through thesclerotomy site may create a potentially open conduitthrough the conjunctival and scleral wound that may facil-itate entry of bacteria into the eye.23

At our institution, we utilize a standardized infectionprevention procedure for all patients in the operatingroom. This protocol includes lid scrubbing with shampooby the operating room nurse in the operating room andpovidone–iodine preparation, including povidone–iodineplaced into the conjunctival fornices by a medical doctor.Application of povidone–iodine preparation directly tothe eyes has been demonstrated in well-controlled studiesto decrease the ocular microbiologic flora before intraoc-ular surgery.24,25

Because the initial 25-gauge PPV safety trials were car-ried out at University of California, Los Angeles and othercenters (Chen et al, IOVS 2005, v 46; Mango et al IOVS2005, v 46), we have adopted standardized guidelines spe-cifically for 25-gauge surgical cases that we feel may im-prove safety. First, all eyes undergoing 25-gauge PPV re-ceive subconjunctival, non-aminoglycoside antibiotic andsteroid injections at the end of the case. The antibiotic ismeant to be injected over the sclerotomy sites to both

Figure 1. Injection of subconjunctival antibiotic may reposit the vitreou

deliver antibiotics to the eye and to reposit any vitreous that

may be prolapsed out of the conjunctival incision (Fig 1).Second, air or gas tamponade is liberally used to minimizehypotony. Shimada et al12 observed low intraocular pres-sure in only 9% of eyes left with air or gas compared with20% of eyes left with fluid, suggesting the different surfacetension of gas compared with fluid may help to close thesclerotomy from the inside, minimizing hypotony. Third,there is a low threshold to move to larger gauge surgery inmore complex cases. We hypothesize that these safety mea-sures may allow for safe and successful 25-gauge PPV.

In this study, we sought to compare the incidence ofendophthalmitis at our institution after 20- and 25-gaugePPV. Herein, we report a low rate of postoperative endoph-thalmitis after 20- and 25-gauge PPV, and we were unableto show any significant difference in postoperative endoph-thalmitis rates when comparing 20- to 25-gauge PPV.

Material and Methods

We retrospectively reviewed the charts of all consecutive patientswho underwent 20- or 25-gauge PPV at the Jules Stein EyeInstitute from January 2002 to January 2008. Patients were iden-tified and included based on procedure codes within the hospitalbilling database. Institutional Review Board approval was ob-tained. The time period analyzed was chosen before formal reviewof cases of endophthalmitis.

Exclusion criteria were a preoperative diagnosis of currentintraocular infection (e.g., cataract surgery associated endoph-thalmitis, endogenous endophthalmitis, acute retinal necrosis, cy-

into the subconjunctival space.

tomegalovirus retinitis), vitrectomies performed for the purpose of

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Ophthalmology Volume 116, Number 7, July 2009

drug delivery device implantation in the posterior segment, and25-gauge PPVs in which all sclerotomies were sutured closed.

A 20-gauge sclerotomy was defined as a 20-gauge pars planascleral incision created with the microvitreoretinal blade afterconjunctival peritomy. At the end of surgery, all 20-gauge scle-rotomies were sutured closed.

A 25-gauge sclerotomy was defined by placement of a 25-gauge trocar-cannula directly through conjunctiva, sclera, and parsplana. The conjunctiva was displaced before trocar-cannula inser-tion in the majority of cases. Trocars were removed at the conclu-sion of the case. A sclerotomy was sutured closed if leak wassuspected by the operating surgeon. In this study, only 25-gaugePPVs having �1 sutureless sclerotomy at the end of the case wereincluded for analysis.

Postoperative endophthalmitis was defined by the followingwidely accepted clinical criteria: progressive eye pain, anteriorchamber cell with fibrin, hypopyon, vitreous cells and fibrin, anddecreased vision occurring within 6 weeks of PPV. Positive cultureresults were not necessary for the diagnosis of postoperative en-dophthalmitis, given the high false-negative rate of intravitrealsampling.4,16,17,26

All PPV were performed by Jules Stein Eye Institute retinadivision faculty (n � 7) with the assistance of retina fellows (n �11) using identical infection prevention measures detailed below.Preoperative preparation included eyelid and periorbital scrubbingwith shampoo (Johnson’s Head-to-Toe Baby Wash, Johnson &Johnson Consumer Product Company, Skillman, NJ) followed bysterile preparation with povidone–iodine 10% solution (PovidoneIodine USP Prep Solution, Novation, Inc. Irving, TX) diluted 1:1with sterile saline, using standard sterile technique. Before prep-aration, the operator washed hands with sterile scrub technique andwore sterile gloves. Sterile cotton gauze soaked in povidone–iodine 5% solution was applied in a progressively outward circularmotion around the surgical area. All patients were draped in asterile fashion, everting lashes from the operative field using anadhesive lash drape and a lid speculum. During the operation,standard instrumentation was used and no antibiotic was added tothe infusion fluid. At the end of the operation, subconjunctivalantibiotics (cephalosporin) and steroid (dexamethasone) are given.The antibiotics were meant to be injected to form 3 separateconjunctival blebs over each of the 3 sclerotomy sites. Subcon-junctival cephalosporin antibiotic was used in patients allergic topenicillin. Patients routinely received postoperative topical fluoro-quinolone, prednisolone acetate 1%, and atropine 1% for �1 week.No oral antibiotics were given for ophthalmologic indicationsduring the perioperative period.

Data collected for each PPV were patient age, eye laterality,incision gauge, suture status of sclerotomies, endotamponade agent,use of intraoperative triamcinolone, and postoperative follow-upinterval. Adequate follow-up was defined as patients with follow-upinterval of �1 week. The proportion of patients with adequatefollow-up in each group was calculated.

We identified any endophthalmitis by 2 overlapping, redundantmethods: a computer database was searched for all encounters andprocedures coded for infectious endophthalmitis (360.00, 360.01,360.03, 360.04, and 360.19), and comprehensive computerizedreview of each patient’s record was performed to identify anyfollow-up procedures that were performed for the treatment ofpostoperative infection.

For any patient who met clinical criteria for endophthalmitis,microbiologic cultures were performed on vitreous and/or anteriorchamber aspirates and the following data were further collected:presenting and last follow-up visit visual acuity, intraocular pres-sure on the first postoperative day, pain, interval from PPV topresentation, microbiologic data, antibiotics administered, and pa-

tient’s intraocular surgical history within 6 weeks before PPV.

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Vitreous and/or aqueous samples were analyzed by the microbi-ology laboratory at University of California, Los Angeles MedicalCenter (Los Angeles, CA).

We compared the incidence of endophthalmitis in 20- versus25- gauge PPV by the Fisher exact test and calculated confidenceintervals by percentage of binomial distribution. Other proportionswere also compared using Fisher exact testing. Means were com-pared using the Student t test, and medians were compared byWilcoxon rank-sum test.

Results

Of 3597 PPVs reviewed, 3445 met inclusion and exclusion crite-ria. Forty-one were excluded because they were 25-gauge cases inwhich all sclerotomies were sutured closed (predominantly pedi-atric cases; none of these developed endophthalmitis). Amongthese 3445 PPVs, the number of patients with adequate follow-upwas 1948 (97.3%) and 1424 (98.7%) in the 20- and 25-gaugegroups, respectively (Table 1). There was no significant differ-ence in the proportion of patients with adequate follow-upbetween 20- versus 25-gauge groups (Fisher exact test; P �0.79; Table 1).

Among these 25-gauge cases (n � 1424), �1 sclerotomy wassutured in only 70 (5%) cases. Patients undergoing 20-gauge PPVwere younger than those undergoing 25-gauge PPV (P�0.0001).The median (range) post-PPV follow-up time in both groups wasbeyond the time expected for development of acute postoperativeendophthalmitis (Table 1).

None of the 20-gauge PPV cases had endophthalmitis. Only 1in 1424 (0.07%; 95% confidence interval [CI], 0%–0.21%) casesof 25-gauge PPV developed endophthalmitis. There was no statis-tically significant difference in endophthalmitis incidence betweenthe 2 groups (Fisher exact test; P � 0.42).

Intravitreal triamcinolone was used �3 times as often during25- versus 20-gauge surgery (13.6% vs 3.7%; P�0.001). Air orlonger acting gases were more likely to be used in 25- comparedwith 20-gauge PPV (68.4% vs 38.8%; P�0.0001). For 20-gaugesurgery, silicone oil was the most commonly used endotamponadeagent and was more likely to be used in 20- compared with25-gauge PPV (35.3% vs 2.0%; P�0.0001; Table 2).

The endophthalmitis patient was a 66-year-old, nondiabetic,phakic woman with preoperative best-corrected visual acuity of20/200 who underwent uncomplicated 25-gauge PPV, membranepeel, indocyanine green staining with internal limiting membrane

Table 1. Baseline Characteristics of 25- and 20-Gauge ParsPlana Vitrectomies at a Single Center over Multiyear Period

25-Gauge(n � 1443)

20-Gauge(n � 2002) P

No. of patients (%) withadequate follow-up

1424 (98.7) 1948 (97.3) 0.79*

Mean age (� SD), yrs# 64.4 (� 16.5) 54.6 (� 22.6) �0.0001†

Median follow-upduration (range), mos#

13.0 (0.25–72.0) 12.5 (0.25–74.6) 0.69‡

SD � standard deviation.Adequate follow-up defined as a follow-up interval of �1 week aftervitrectomy surgery.*Fisher exact test, 2-tailed.†Student t test, 2-tailed, 2 samples of unequal variance.‡Wilcoxon rank-sum test.#

Analysis includes only patients with adequate follow-up.

Hu et al � Endophthalmitis after Vitrectomy

peel, air–fluid exchange, and placement of 14% C3F8 gas for astage 4 macular hole in February 2005. Three disposable instru-ments were used in addition to the vitrectomy probe and light pipe.Intraoperative intravitreal triamcinolone was not administered. Post-operative day 1 intraocular pressure by applanation tonometry was16 mmHg. No conjunctival bleb or leak was noted. Four days afterthe surgery, the patient complained of decreased vision and in-creased pain. Visual acuity was hand motion with associatedconjunctival injection, 1.2 mm hypopyon, anterior chamber fibrin-ous reaction, and 85% gas fill. A vitreous sample was obtained.The patient was treated with intravitreal vancomycin (1 mg/0.1mL), ceftazidime (2.25 mg/0.1 mL), dexamethasone (400 �g/0.1mL) injections, and fortified topical antibiotics (vancomycin andtobramycin). Microbiologic cultures were negative. Visual acuityimproved and pain decreased after 2 days of treatment. Visualacuity at 3 months was 20/200, and the macular hole was closed.

Discussion

Microincisional, sutureless surgery is an increasingly pop-ular technique among vitreoretinal surgeons. Despite poten-tial advantages such as less ocular surface disruption andfaster postoperative recovery, 2 recent studies have reportedhigher rates of endophthalmitis after 25- compared with20-gauge PPV.16,17 In contrast, we were unable to find anysignificant difference in the incidence of endophthalmitisafter 25- versus 20-gauge PPV in our study population(Table 3).

Our study highlights the infection prevention steps thatmay lead to a low incidence of endophthalmitis after 25-gauge PPV. Our center implemented standardized infection

Table 2. Intraoperative Characteristics of 25- and 20-GaugePars Plana Vitrectomies at a Single Center over

Multiyear Period

25-Gauge(n � 1424)

20-Gauge(n � 1948)

P-Value ofComparison of

25- vs 20-Gauge

Intravitrealtriamcinolone

193 (13.6%) 73 (3.7%) �0.001*

Silicone oil 29 (2.0%) 683 (35.1%) �0.0001†

Fluid 421 (29.6%) 509 (26.1%)SF6 gas 161 (11.3%) 185 (9.5%)C3F8 gas 217 (15.2%) 400 (20.5%)Air 596 (41.9%) 171 (8.8%)

*Fisher exact test.†Chi-square test; single-tailed; degrees of freedom � 4.

Table 3. Comparison of Endophthalmitis InVitrectomy in Recen

Kunimoto e(18 surgeons, 1

20-Gauge endophthalmitis incidence 1/5498 � 0.025-Gauge endophthalmitis incidence 7/3103 � 0.2P value* 0.004

*Calculated by Fisher exact test, 2-tailed.

prevention protocols �2 decades ago. These were utilizedcontinuously throughout the period studied. Specifically,preoperative application of povidone–iodine directly ontothe ocular surface and fornices has been shown significantlyto reduce species and colony counts. Moreover, routine useof subconjunctival antibiotics over each sclerotomy at theend of surgery may be especially relevant in 25-gauge casesbecause the sclerotomies are not routinely sutured closed.An exposed vitreous wick may extend from the intraocularcavity through the sclerotomy into the extraconjunctivalspace. Subconjunctival antibiotic or steroid injection maymechanically aid in repositing potential extraconjunctivalvitreous wick into the subconjunctival space. Because thedistal end of the vitreous wick is not exposed to the con-junctival and ocular surface, this maneuver may eliminate aroute by which organisms in the external environment maygain access into the intraocular cavity (Fig 1). Althoughprevious studies note the frequent use of subconjunctivalantibiotics, this technique was not part of a uniform protocoland subconjunctival antibiotics were not injected directlyover each sclerotomy.16,17 Further studies are needed tovalidate how much these methods contribute to infectionprevention.

Although our study is not designed to show that air/gasendotamponade reduces hypotony and may lower risk ofendophthalmitis, the high proportion of air/gas endotam-ponade use in our 25-gauge PPV coupled with the lowincidence of endophthalmitis suggests a possible correla-tion. The proposed mechanism by which the different sur-face tension of air/gas compared with fluid may help to sealthe sclerotomy from the inside is plausible.12 Another ad-vantage is that fluid–air exchange at the end of the surgerymaintains early postoperative intraocular pressure and limitsthe influx of bacteria that may cause infection.27 Furtherstudies may be warranted to validate how the choice ofendotamponade agents may affect endophthalmitis rates.

There are strengths to our study methodology. First, ourdata span a multiyear time frame and include both early andmore recent experiences with 25-gauge PPV. With rareevents like endophthalmitis, a cluster of cases can give themisleading appearance of higher endophthalmitis rates. Sec-ond, all cases had �1 week of follow-up and the vastmajority of patients were followed beyond the mean time topresentation of acute endophthalmitis after 25-gauge PPVreported in previous studies. In fact, in 7 of 8 and 10 of 11endophthalmitis cases reported by Kunimoto et al and Scottet al, respectively, the patients presented with pain and othersymptoms within 5 days after surgery.16,17 Our minimum

ce Rates after 20- and 25-Gauge Pars Planaublished Case Series

er)Scott et al17

(8 surgeons, 7 centers)Hu et al

(7 surgeons, 1 center)

2/6375 � 0.03% 0/1948 � 0%11/1303 � 0.84% 1/1424 � 0.07%

�0.001 0.42

cidently P

t al16

cent

18%3%

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Ophthalmology Volume 116, Number 7, July 2009

follow-up period of 1 week encompasses the relevant riskperiod for postoperative endophthalmitis, and follow-upintervals were statistically equivalent between the 25- and20-gauge PPV groups. Third, baseline characteristics weregenerally well-balanced between the 2 groups. Althoughpatients undergoing 20-gauge surgery were younger, thereis no association between age and endophthalmitis rate inour cohort or in the previously published series on 25-gaugePPV endophthalmitis.16,17 No official case selection criteriawere applied because cases were deemed appropriate for25-gauge surgery at the discretion of the individual surgeon.Granted, the list of diagnoses considered appropriate for25-gauge surgery was much narrower during earlier expe-riences with smaller gauge surgery; however, as surgeonsgained more experience with 25-gauge surgery, the indica-tions broadened as surgery was felt to be safe and efficient.In addition, we did not exclude 25-gauge cases that werepartially converted to 20-gauge surgeries; therefore, pre-sumably more complex and challenging cases were alsoincluded in the 25-gauge group. Even if we assume that acase selection effect resulted in more complex cases beingassigned to 20-gauge PPV, we would have expected a muchhigher incidence of endophthalmitis in the 20-, instead ofthe 25-gauge, PPV group. However, this was not observedin our cohort.

Nevertheless, the absence of significant difference shouldbe interpreted with caution. First, cases of endophthalmitismay not have been identified owing to the retrospective natureof the study. However, every single patient record was re-viewed by 2 overlapping, redundant methods to identify po-tential endophthalmitis cases. In addition, given that all PPVswere performed during the same time period, and the propor-tion of patients with adequate follow-up was statistically equiv-alent in both groups, any ascertainment bias resulting frominadequate follow-up would equally affect both groups, andshould not affect the relative incidences of endophthalmitis ina comparative study. Also, there is no reason to believe thatthere would be any association between lack of follow-up anddevelopment of endophthalmitis. In fact, patients with endoph-thalmitis are usually symptomatic and should be even morelikely to return for follow-up examination. Second, we re-viewed fewer 25-gauge cases than 1 previously reportedstudy.16 Owing to the relative infrequency of the conditionunder investigation, all investigations of this nature are inher-ently limited by low power. Nevertheless, the upper limit of the95% confidence interval for our 25-gauge endophthalmitis rate(0.21%) was lower than previously reported rates of 0.23% to0.84%.16,17 Furthermore, to detect a difference between the0.84% rate in 1303 eyes observed in the series by Scott et al17

and the 0.07% in 1424 eyes in our series using a 2-sided Fisherexact test at an � level of 0.05, the power is 85%, suggestingthat the lower rate of 25-gauge endophthalmitis observed inour cohort may be truly lower than that observed in previousstudies (Table 3).

In summary, we were unable to find a statistically sig-nificant difference in the incidence of endophthalmitis inpatients undergoing sutureless 25-gauge versus sutured 20-gauge PPV. This study also emphasizes the potential role ofspecific infection prevention measures including lid scrub-

bing, povidone–iodine application, conjunctival displacement,

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and repositing potential extraconjunctival vitreous during sub-conjunctival antibiotic injection. The low incidence of endoph-thalmitis after sutureless 25-gauge vitrectomy in this studymay dampen the recent concerns regarding the higher inci-dence of endophthalmitis after 25-gauge PPV.

Acknowledgments. The authors acknowledge Fei Yu, PhD, forhis contributions to the statistical analyses.

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Footnotes and Financial Disclosures

Originally received: September 6, 2008.Final revision: January 29, 2009.Accepted: January 29, 2009. Manuscript no. 2008-1074.

1 Retina Division, Jules Stein Eye Institute, Department of Ophthalmology,University of California, David Geffen School of Medicine, Los Angeles,California.

2 Paris Descartes University, Faculty of Medicine, Hotel-Dieu Hospital,Assistance Publique des Hopitaux de Paris, Paris, France.

Presented at: American Society of Retina Specialists Meeting, Maui,

Financial Disclosure(s):Anurag Gupta (C, L) Alcon; Bausch and Lomb. Christine R. Gonzales (C, L)Alcon; Bausch and Lomb. Steven D. Schwartz (C, L) Alcon; Bausch andLomb.

Funding was provided by the Retina Division, Jules Stein Eye Institute,UCLA and by the Frederick G. Rappaport Fellowship Award to Scott C. N.Oliver, MD.

Correspondence:Steven D. Schwartz, MD, Jules Stein Eye Institute, Retina Division,UCLA, 100 Stein Plaza, Los Angeles, CA 90095-7000. E-mail: schwartz@

jsei.ucla.edu.

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