Current Incidence of Retinopathy of Prematurity, 1989–1997

Naveed Hussain, MBBS, DCH*; Jonathan Clive, PhD‡; and Vineet Bhandari, MD, DM*

ABSTRACT. Objective. To report the current inci-dence and the need for surgery for retinopathy of prema-turity (ROP) in neonates (22–36 weeks’ gestational age[GA], July 1, 1989 through June 30, 1997).

Study Design. Retrospective analyses using comput-erized perinatal database kept on all admissions, a re-view of patient charts, and eye examination log books.

Setting. Level 3 regional referral NICU.Patients. A total of 2528 infants <37 weeks’ GA were

admitted during this time. Of these infants, 950 met thecriteria for eye examination beginning at 4 to 6 weeks ofage and repeated every 2 weeks until complete vascular-ization of the retina or death or discharge.

Results. The incidence of ROP was (202/950) 21.3%for any stage and 4.6% (44/950) for stage 3 ROP or greater.No ROP was noted in infants born at >32 weeks’ GA. Noinfant born at >28 weeks needed retinal surgery. Usingbirth weight (BW) criteria, stage 3 ROP was not noted ininfants with BWs >1500 g; retinal surgery was notneeded in infants with BWs >1000 g. A number of peri-natal factors were associated with ROP on univariateanalysis. However, using multiple logistic regressionanalyses of these factors, only GA and days on supple-mental oxygen therapy were associated significantlywith the development of ROP. Despite increased sur-vival of extremely low BW infants, we found a consider-able reduction in incidence and severity of ROP com-pared with reports from an earlier chronological period.However, infants <28 weeks’ GA or with BWs <1000 gwere still at considerable risk for retinal surgical treat-ment for ROP.

Conclusion. We conclude that the incidence and se-verity of ROP have decreased significantly in the presentera of surfactant therapy. Pediatrics 1999;104(3). URL:http://www.pediatrics.org/cgi/content/full/104/3/e26; reti-nopathy, prematurity, incidence, morbidity, eye.

ABBREVIATIONS. ROP, retinopathy of prematurity; LBW, lowbirth weight; NICU, neonatal intensive care unit; RDS, respiratorydistress syndrome; GA, gestational age; BW, birth weight; SGA,small for gestational age; IVH, intraventricular hemorrhage; PVL,periventricular leukomalacia; BPD, bronchopulmonary dysplasia;NEC, necrotizing enterocolitis; CPAP, continuous positive airwaypressure.

Retinopathy of prematurity (ROP) is a signifi-cant problem in low birth weight (LBW) pre-mature infants. Before surfactant became

available for clinical use in the neonatal intensivecare unit (NICU), an incidence of 11% to 60% wasreported in the LBW population.1,2 The last majorreport of the incidence of ROP was published fromthe cryotherapy–retinopathy of prematurity (CRYO-ROP) study completed in 1987,3 which was con-ducted before surfactant use was approved for treat-ment of respiratory distress syndrome (RDS). Adecade of continued advances in neonatal manage-ment, including the use of surfactant therapy andnew methods of mechanical ventilation has im-proved most neonatal outcomes, but scarce data areavailable regarding the current incidence of ROP. Itis also not clear whether the increased survival ofsmaller and sicker infants has resulted in an in-creased proportion of infants needing retinal surgerybecause of ROP.4,5 In their recent comprehensive re-view of ROP, Siatkowski and Flynn6 noted that “weare as lacking in basic epidemiologic data of varyingrates of incidence [of ROP] in geographic areas . . . aswe were in the 1940s and 1950s.” The goals of thepresent study are 1) to report the current incidence ofROP and the need for retinal surgery for severe ROPfrom a regional NICU and 2) to evaluate the contri-bution of various perinatal and neonatal factors tothe risk for ROP.

METHODS

SubjectsThe John Dempsey Hospital of the University of Connecticut

Health Center is a high-risk perinatal center and a regional referralNICU for the northern two thirds of Connecticut. It is the largestof three tertiary care units for this region of Connecticut. Thepopulation profile of infants admitted reflects that of other similarcenters in the United States with 75% white, 13% black, and 9%Hispanic infants.7 There were no significant changes in referralpatterns or the proportion of premature infants admitted over thestudy period. This was a retrospective study of all 22 to 36 weeks’gestational age (GA) premature infants who were admitted to theNICU between July 1, 1989 and June 30, 1997. Surfactant becameavailable in this center in 1989 as an investigational drug initiallyand then for routine use after Food and Drug Administrationapproval in 1991. Of the 5526 infants admitted during the 9-yearstudy period, 2528 were #36 weeks’ GA. Of these infants, 950neonates met the criteria to have their eyes examined by pediatricophthalmologists to detect ROP. Data were collected on theseinfants from a combined review of a computerized database kepton all admissions to the NICU, from a review of patient records,and from log books kept to record the results of eye examinationsby ophthalmologists.

Eye Examination ScheduleThe eye exams were performed for all infants who met the

following criteria: 1) infants ,30 weeks’ GA or ,1300 g at birth; 2)

From the Department of *Pediatrics; and the ‡Office of Biostatistical Con-sultation, University of Connecticut, School of Medicine, John DempseyHospital, Farmington, Connecticut.Received for publication Jul 7, 1998; accepted Apr 5, 1999.Reprint requests to (N.H.) University of Connecticut School of Medicine,Department of Pediatrics, Division of Neonatology, John Dempsey Hospi-tal, Farmington, CT 06030-2498. E-mail: hussain@nso1.uchc.eduPEDIATRICS (ISSN 0031 4005). Copyright © 1999 by the American Acad-emy of Pediatrics.

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infants ,35 weeks’ GA or ,1800 g at birth who received supple-mental oxygen for .1 week; and 3) any newborn who remained insupplemental oxygen for .60 days. Infants first were examined bythe ophthalmologists at 4 to 6 weeks of age. They then werefollowed by eye examinations every 1 to 2 weeks until death ordischarge or until retinal vascularization was complete.

Eye Examination MethodThe pupils were dilated with 0.5% tropicamide and 2.5% phen-

ylephrine, the infant was swaddled, and the ophthalmic funduswas examined by indirect ophthalmoscopy with a 130 diopteraspheric lens. An infant eye speculum and scleral indentationwere used as needed to view the retinal periphery. Observationswere classified according to the International Classification ofRetinopathy of Prematurity.8 In brief, the stages of ROP were:

• Stage 1. Demarcation-line separating the avascular retina ante-riorly from the vascularized retina posteriorly with abnormalbranching of small vessels immediately posterior to this.

• Stage 2. Intraretinal ridge: the demarcation line has increased involume, but this proliferative tissue remains intraretinal.

• Stage 3. Ridge with extraretinal fibrovascular proliferation.• Stage 4. Partial retinal detachment.• Stage 5. Total retinal detachment.

The zone of vascularization was noted. The number of total andcontiguous clock hours of ROP and the presence or absence ofPlus disease (tortuosity of veins) were important determinants ofmanagement.

Results of eye examinations were entered into a log book and acomputerized database. The same team of 3 experienced pediatricophthalmologists performed all of the examinations. Infants whowere transferred back to the referring hospital were examined atleast once by the same group of ophthalmologists in .90% of thecases. No infant with significant active ROP was back transferreduntil regression of ROP was noted. The few infants who weretransferred out of the NICU with immature zone 2 were followedup by the same group of ophthalmologists (none of these infantsdeveloped threshold ROP subsequently). The maximum severityof ROP in any one eye for an individual infant was recorded foranalysis. In infants with severe disease, the same group of oph-thalmologists and retinal surgeons who confirmed the need forretinal ablative surgery (cryotherapy or laser surgery) performedthe procedure and were responsible for the infant’s subsequentfollow-up.

Monitoring and Management of Infants at Risk forROP

MonitoringIf no ROP was noted, eye examinations were continued every 2

weeks until retinal vascularization extended to zone 3. The thresh-old for treatment was determined by the protocol that was usedfor the CRYO-ROP trials.3 Briefly, prethreshold ROP was zone 1ROP of any stage less than threshold; zone 2 stage 2 ROP orgreater; zone 2 ROP stage 3 without Plus disease; and zone 2 stage3 ROP or greater with fewer than the threshold number of sectorsof stage 3 or greater. This was observed closely until resolution oruntil progression to threshold ROP. Threshold ROP needing sur-gery was 5 or more contiguous or 8 cumulative clock hours ofstage 3 ROP or greater in either zone 1 or zone 2.

ManagementAll premature infants were given vitamin E 25 international

units per day from the time full enteral feeds were establisheduntil 36 weeks’ postmenstrual age or until discharge. Infants werecared for in a low illumination environment with cloth covers overisolettes. No eye shields were used except when infants werereceiving phototherapy. At all times during NICU care, supple-mental oxygen was given to maintain pulse oximetry between90% and 95%, and no increase or decrease in target pulse oximetrywas made with the identification of any stage of ROP. All infantson supplemental oxygen during the period of observation weremonitored by continuous pulse oximetry.

Identification of Risk FactorsThe following perinatal–neonatal variables were reviewed for

their association with the risk and severity of ROP and the needfor retinal ablative surgery: GA, birth weight (BW), race, type ofdelivery, small for GA (SGA) status, presence of RDS, use ofsurfactant, presence of confirmed sepsis, intraventricular hemor-rhage (IVH), periventricular leukomalacia (PVL), severe broncho-pulmonary dysplasia (BPD), necrotizing enterocolitis (NEC), dayson mechanical ventilation, days on continuous positive airwaypressure (CPAP), days on oxygen, and length of stay in the hos-pital.

DefinitionsGA at birth was assessed as completed weeks using obstetric

estimates based on the date of the last menstrual period of themother confirmed by clinical evaluation of early uterine size andultrasonography of the fetus early in gestation and/or at admis-sion. The majority (70%) of pregnancies in this study had an earlygestation ultrasound for confirmation of dates. Postnatal assess-ment of maturity was not relied on in this study because of itsknown inaccuracies in extremely premature infants.9 Ethnicitywas determined based on maternal race. Infants were deemedSGA if BWs were ,10 percentiles from the 3rd revision of growthcharts by Gairdner and Pearson10 (Castlemead Publications, Hert-fordshire, UK). RDS was defined by the presence of clinical fea-tures and chest radiographic findings. The occurrence of IVH andPVL were determined by cranial ultrasonography at least twotimes within the first 10 days of birth and at least once beforedischarge. Sepsis was established by the growth of organisms inblood culture. NEC was diagnosed based on clinical features andabdominal radiographic changes as described by Bell.11 SevereBPD was defined as the need for supplemental oxygen along withradiographic lung changes beyond 36 weeks’ postmenstrual age.

Statistical AnalysisUnivariate comparisons of risk factors between the two groups

with or without ROP were evaluated using the Student’s t test andthe x2 test as appropriate with statistical significance at P ,.05.Using multiple logistic regression analyses with a step-up meth-odology using variables that were significant on univariate com-parisons, the correct classification rate was determined with theSAS/STAT package (SAS Institute Inc, Cary, NC).12 The correctclassification rate quantifies how well the models of multiplelogistic regression analyses discriminate between ROP and non-ROP groups.

RESULTSBetween July 1, 1989 and June 30, 1997, 5526 in-

fants were admitted to the NICU at John DempseyHospital of the University of Connecticut HealthCenter. The selection of patients from this populationis shown in Fig 1. Of the 950 infants who met thecriteria for evaluation, ROP of any degree was diag-nosed in 202 (21.3%) infants, and 44 (4.6%) infantshad severe stage 3 ROP or greater.

Demographic and Perinatal FactorsIn Table 1, demographic and perinatal factors in

the infants who met the criteria for eye exams aresummarized. Maternal race, male gender, SGA statusat birth, and length of stay were not significantlydifferent among infants who developed any stage ofROP and those who did not. Immaturity reflected bylower BW and GA at birth was a significant factor ininfants who developed ROP. Severity of respiratorydisease, reflected by the number of infants who de-veloped RDS or needed the use of surfactant or re-quired ventilatory, CPAP, or supplemental oxygensupport, was also significantly higher in those whodeveloped ROP. Infants who were diagnosed withROP also developed more IVH and PVL and had a

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significantly higher incidence of sepsis. A lower rateof vaginal delivery in the ROP group probably re-flects the high-risk perinatal status of these immatureinfants near the time of their delivery and the peri-natologist’s decision not to deliver by this route.

Relative Proportions of Infants Dead, Alive, and ThoseWith ROP

Because infants who died before 6 weeks of agecould not be examined for ROP, it is important toshow the relative proportions of infants who lived or

died along with those who developed ROP. This isshown in Fig 2. Infants born at #25 weeks’ GA hadhigh mortality rates, and the proportion of infantswith ROP remained between 30% and 40% of alllive-born infants. In infants born at $26 weeks’ GA,even as the mortality remained relatively low, theproportion of infants developing ROP declined withincreasing GA, thus no infant born at .32 weeks’ GAdeveloped ROP.

Distribution of Stages of ROP by GAFigure 3A shows the relationship between GA and

severity of ROP (percent of infants studied) includ-ing its sequelae. The incidence of ROP in survivors at23 completed weeks was 71.4%; at 24 weeks was70.7%; at 25 weeks was 45.5%, at 26 weeks was44.6%; at 27 weeks was 35.4%; and at 28 weeks was18.6%. Among all infants #28 weeks’ GA, the inci-dence of any stage of ROP was 40.1% (176/439) andof severe ROP (stage 3 or greater) was 9.8% (43/439).Infants with a GA of 23 to 24 weeks were representeddisproportionately in this group. Beyond 28 weeks’GA, severe ROP was virtually nonexistent. Fig 3Bshows the absolute numbers of infants with mild orsevere ROP and the number who needed surgicaltreatment (threshold disease) stratified by GA atbirth in completed weeks. Of the infants examined at.60 days of oxygen requirement, there were nonewho were .36 weeks’ GA.

Distribution of Stages of ROP by BWSimilarly, Fig 4A illustrates the relationship be-

tween BW and severity of ROP as a percentage of theinfants studied. For infants with BWs ,1000 g, the

Fig 1. Schematic diagram of the distribution of infants in the study.

TABLE 1. Population Characteristics and Comparison ofVariables*

ROP(n 5 202)

No ROP(n 5 748)

PValue

GA (wk) 26.1 6 2.1 29.6 6 2.8 ,.0001BW (g) 847 6 224 1344 6 488 ,.0001SGA (n; %) 17 (8.4%) 91 (12.2%) NSWhites (n; %) 150/196† (76%) 549/733† (75%) NSBlacks (n; %) 30/202 (14.9%) 97/748 (13%) NSMale gender (n; %) 96 (48%) 406 (54%) NSVaginal delivery (n; %) 44/197† (22%) 254/741† (34%) .001RDS (n; %) 180/202 (89%) 478/748 (64%) ,.0001Surfactant (n; %) 145 (72%) 333 (45%) ,.0001Severe BPD (n; %) 121 (60%) 231 (31%) ,.0001Ventilator (d) 29.7 6 21 8.9 6 15 ,.0001CPAP (d) 14.9 6 16 7.9 6 12 ,.0001Oxygen (d) 85.7 6 50 38.7 6 42 ,.0001NEC (n; %) 15 (7%) 37 (5%) NSSepsis (n; %) 79 (39%) 123 (16%) ,.0001IVH (n); %) 16 (8%) 23 (3%) .004PVL (n; %) 10 (5%) 12 (2%) .01Length of stay 71.2 6 38 76 6 44 NS

* Univariate comparisons of demographic and perinatal factors ininfants who developed any stage of ROP and those who did not.† Missing data. Data shown as mean 6 SD.

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incidence of ROP of any degree was 46% (160/347)and of severe ROP stage 3 or greater was 12% (42/347). The 2 infants with BWs .1000 g who developedstage 3 ROP did not reach the threshold for retinalsurgery with laser or cryotherapy.

Figure 4B shows the absolute number of infantswith mild or severe ROP and the number who re-quired surgery stratified by 500 g BW categories.

Multiple Logistic Regression AnalysisBecause most of the risk factors are functions of

immaturity, a multiple logistic regression model wasdesigned with BW, GA, days on oxygen, surfactantuse, and the incidence of sepsis to study the inde-pendent contribution of these factors to the develop-ment of ROP. Results are shown in Table 2. Only GAand days on supplemental oxygen entered themodel. The chances of not developing ROP in thewhole population were 78.7%; and GA by itself coulddiscriminate this group at 81.6% correct classificationrate. The addition of information on days on supple-mental oxygen increased this to 82.34%. The statisti-cal addition of surfactant use and/or episodes ofconfirmed sepsis to GA did not improve further thecorrect classification rate.

Changes in Incidence of ROP With TimeFigure 5 shows that there was an increase in the

percentage of non-ROP infants with a concomitantdecrease in stage 1 and 3 ROP between 1989 and1991 (x2; P ,.0001). This was noted despite animprovement in survival of smaller infants.13 The

notable change in care of premature infants thatoccurred during 1991 was the introduction of sur-factant replacement with Survanta (Ross Products,Columbus, OH) for treatment of RDS. Some infantswere given surfactant under an investigationalnew drug protocol between 1989 and 1990.

DISCUSSIONThis report represents the first comprehensive

study of the incidence and severity of ROP, sincesurfactant use has become common clinical practicefor the treatment of RDS in the United States.

The impact of ROP on vision in the prematureinfant has been well appreciated since the early re-port by Terry.14 Its changing incidence has been re-lated to changes in clinical practice.15 Recent reportsfrom Europe and Australia suggest a decreasing in-cidence of severe ROP, but data on the differentstages of ROP and on the relative occurrence of dif-ferent stages are not reported.2,5 The CRYO-ROPmulticenter study (1986–1987)3 showed that amonginfants with BWs ,1251 g, 65.8% developed ROP tosome degree, and the incidence was 81.6% in infants,1000 g. This study also analyzed the incidencestratified by GA in a separate report.16 Since thatlarge study, there have been no major reports pub-lished on the incidence of ROP from the UnitedStates, although it is well recognized that the recentchanges in the care of premature infants (surfactant,improved understanding of physiology, improvedtechnology, and better modalities of neonatal venti-

Fig 2. Relative percentage of live-born infants who died, lived, or developed ROP stratified by completed weeks’ GA. Data fromUniversity of Connecticut Health Center from July 1989 to June 1997. Sample size is shown at the top of each bar.

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lation) may impact the incidence and severity of thiscondition.17

The present study shows a significant decrease in

the incidence and severity of ROP from previousreports.3,16 The overall incidence in infants with BWs,1251 g was 34% (187/545), and the incidence

Fig 3. A, Distribution of percent incidence and severity of ROP stratified by GA (22–36 weeks) from 1989 to 1997. Sample size is shownat the top of each bar. B, Absolute number of infants with ROP who required retinal surgery (threshold, needing retinal ablative surgery)compared with less severe disease stratified by GA (22–36 weeks) from 1989 to 1997.

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among infants with BWs ,1001 g was 46% (160/347), which is approximately half of the incidencereported in the CRYO-ROP study.3 Moreover, none

of the infants in our study with BWs .1000 g reachedthe threshold for laser or cryotherapy.

Similarly, the incidence of ROP of any degree in

Fig 4. A, Distribution of percent incidence and severity of ROP stratified by BW (in 500-g increments) from 1989 to 1997. Sample size isshown at the top of each bar. B, Absolute number of infants with ROP who required retinal surgery (threshold, needing retinal ablativesurgery) compared with less severe disease stratified by BW (,750 to .1500 g) from 1989 to 1997.

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infants ,28 weeks’ GA was decreased from 70%(CRYO-ROP)3,16 to 38.7% in this study. The incidenceof ROP that required surgery also was reduced byhalf. This reduced incidence and severity has oc-curred despite an increase in the survival rates of thesmallest and the most vulnerable infants.13,18

In this study, we also report demographic factorsthat may be important in the development of ROP.The population distribution of white and black indi-viduals was similar to the national demographics ofthe United States.7 However, an earlier report statingthat non-black individuals were more vulnerable toROP19 was not confirmed by this study (Table 1).There were also no significant gender differences inincidence of ROP. This confirms the observations ofprevious investigators.2,3

It has been reported that infants who are born SGAmay be more likely to develop ROP.20 This could notbe confirmed by the analysis of our data. We believethat the cause rather than the condition of growthretardation may be a more important factor. Thisassociation needs to be studied in a larger populationbase stratified by the causes of growth retardationbefore any conclusions can be drawn.

A recent report linked an increased incidence ofROP to candidal sepsis.21 Univariate analysis of our

data showed that culture-positive sepsis of any eti-ology was associated significantly with ROP but thatmultiple logistic regression analysis with BW, GA,and days on supplemental oxygen failed to show itsindependent or additional contribution to the risk ofROP. The association between sepsis and ROP needsto be studied in greater detail to delineate any inde-pendent influence of infection.

Respiratory immaturity with RDS along with thelonger duration of use of mechanical ventilation,CPAP, and supplemental oxygen were related sig-nificantly to the incidence and severity of ROP in ourstudy. These factors have been implicated from theearliest reports that linked ROP to oxygen use. Mul-tiple regression analysis of these variables along withGA or BW in our data showed that only days onsupplemental oxygen with GA could enter the modeland predict the risk for ROP independently.

There are variable reports regarding the use ofsurfactant and incidence of ROP. Repka et al17 sug-gested that surfactant prophylaxis will not changethe incidence of ROP, and Rankin et al22 reportedthat surfactant therapy was not associated with anincreased incidence or severity of ROP. The higheruse of surfactant in infants with ROP probably rep-resents the greater pulmonary immaturity of thispopulation. Moreover, the decrease in mortality ofpremature infants with this therapy probably con-tributes to the increase in the number of infants atrisk. In our study, a multiple logistic regression anal-ysis with BW, GA, days on supplemental oxygentherapy, and use of surfactant failed to show anindependent contribution by this treatment. How-ever, it is worth noting that in our analysis of thechanging incidence of ROP during the years of ourstudy, a significant (x2; P ,.0001) decrease in inci-dence and severity of ROP occurred between 1989and 1991 (by which time oxygen saturation monitor-ing was already routine in our center) that coincides

Fig 5. Changing trends in the percentincidence and severity of ROP duringeach year of the study period. The as-terisk indicates x2. P , .0001.

TABLE 2. Correct Classification Rate to Discriminate Signifi-cant Factors That Help Categorize ROP After Multiple LogisticRegression Analysis

Variables Correct Classification Rate(%)

Percent of infants without ROP 78.71GA 81.61GA1 days on oxygen 82.341GA1surfactant 82.01GA1sepsis 81.61GA1surfactant 1sepsis 82

* A number of models were fit using the variables studied. OnlyGA and days on supplemental oxygen entered the model.

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with the Food and Drug Administration-approvedintroduction of surfactant replacement therapy fortreatment of RDS in 1991. There seems to have beenno additional change in the decreased incidence orseverity of ROP from 1991 to the present.

A recent retrospective report of infants born be-tween 1990 and 1996 by Wright et al23 from a singlecenter in the United States shows an incidence ofROP that was much higher than our study reports;however, the trend toward a decrease in incidencefrom previous reports is similar. The details of man-agement of ROP are not provided in this report, andtherefore, it is difficult to comment on the possiblefactors involved.

In our set-up, we take care of a large population ofpremature infants of various ethnicity and socioeco-nomic backgrounds who are given a similar patternof care in a single tertiary center. There have been nosignificant changes in population or in referral pat-terns of the premature infants admitted over the 9years that these data were collected. Therefore, webelieve that the significant decrease in the incidenceand severity of ROP that we report, which has beenconsistent over a number of years, reflects a truechange and would be corroborated from similar re-ports from other centers.

CONCLUSIONWe conclude that the incidence and severity of

ROP have considerably decreased in the presenttimes. It is possible that the primary determinant inthis decrease in incidence of ROP is the improvedunderstanding of the pathophysiology of prematureinfants and the various means of improved support-ive care, such as the surfactant replacement therapy,that contribute to better stabilize the immature organsystems of premature infants and to decrease thewide fluctuations in homeostasis that recently havebeen shown to impact on retinal vascular develop-ment.24,25

ACKNOWLEDGMENTSWe thank Marlene Holman, MSN and Ted Rosenkrantz, MD

for help with the neonatal database; Rachel Schmitt, MSN (dis-charge coordinator) for keeping track of infants needing eye ex-aminations; and our team of pediatric ophthalmologists, Drs May-nard Wheeler, Paul Mitchell, and Peter Walden for keepingmeticulous eye examination records. We also thank Drs MarilynSanders and Maynard Wheeler for their critical review of themanuscript.

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1999;104;e26PediatricsNaveed Hussain, Jonathan Clive and Vineet Bhandari

1997−Current Incidence of Retinopathy of Prematurity, 1989  

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rights reserved. Print ISSN: 0031-4005. Online ISSN: 1098-4275.Grove Village, Illinois, 60007. Copyright © 1999 by the American Academy of Pediatrics. All and trademarked by the American Academy of Pediatrics, 141 Northwest Point Boulevard, Elkpublication, it has been published continuously since 1948. PEDIATRICS is owned, published, PEDIATRICS is the official journal of the American Academy of Pediatrics. A monthly

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1999;104;e26PediatricsNaveed Hussain, Jonathan Clive and Vineet Bhandari

1997−Current Incidence of Retinopathy of Prematurity, 1989  

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