Retinopathy of prematurity. A randomized, prospective trial of transcutaneous oxygen monitoring

Automated oxygen delivery for preterm infants with respiratory dysfunction

BACKGROUND

Many preterm infants require respiratory support to maintain an optimal level of oxygenation, as oxygen levels both below and above the optimal range are associated with adverse outcomes. Optimal titration of oxygen therapy for these infants presents a major challenge, especially in neonatal intensive care units (NICUs) with suboptimal staffing. Devices that offer automated oxygen delivery during respiratory support of neonates have been developed since the 1970s, and individual trials have evaluated their effectiveness.

OBJECTIVES

To assess the benefits and harms of automated oxygen delivery systems, embedded within a ventilator or oxygen delivery device, for preterm infants with respiratory dysfunction who require respiratory support or supplemental oxygen therapy.

SEARCH METHODS

We searched CENTRAL, MEDLINE, CINAHL, and clinical trials databases without language or publication date restrictions on 23 January 2023. We also checked the reference lists of retrieved articles for other potentially eligible trials.

SELECTION CRITERIA

We included randomised controlled trials and randomised cross-over trials that compared automated oxygen delivery versus manual oxygen delivery, or that compared different automated oxygen delivery systems head-to-head, in preterm infants (born before 37 weeks' gestation).

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods. Our main outcomes were time (%) in desired oxygen saturation (SpO2) range, all-cause in-hospital mortality by 36 weeks' postmenstrual age, severe retinopathy of prematurity (ROP), and neurodevelopmental outcomes at approximately two years' corrected age. We expressed our results using mean difference (MD), standardised mean difference (SMD), and risk ratio (RR) with 95% confidence intervals (CIs). We used GRADE to assess the certainty of evidence.

MAIN RESULTS

We included 18 studies (27 reports, 457 infants), of which 13 (339 infants) contributed data to meta-analyses. We identified 13 ongoing studies. We evaluated three comparisons: automated oxygen delivery versus routine manual oxygen delivery (16 studies), automated oxygen delivery versus enhanced manual oxygen delivery with increased staffing (three studies), and one automated system versus another (two studies). Most studies were at low risk of bias for blinding of personnel and outcome assessment, incomplete outcome data, and selective outcome reporting; and half of studies were at low risk of bias for random sequence generation and allocation concealment. However, most were at high risk of bias in an important domain specific to cross-over trials, as only two of 16 cross-over trials provided separate outcome data for each period of the intervention (before and after cross-over). Automated oxygen delivery versus routine manual oxygen delivery Automated delivery compared with routine manual oxygen delivery probably increases time (%) in the desired SpO2 range (MD 13.54%, 95% CI 11.69 to 15.39; I2 = 80%; 11 studies, 284 infants; moderate-certainty evidence). No studies assessed in-hospital mortality. Automated oxygen delivery compared to routine manual oxygen delivery may have little or no effect on risk of severe ROP (RR 0.24, 95% CI 0.03 to 1.94; 1 study, 39 infants; low-certainty evidence). No studies assessed neurodevelopmental outcomes. Automated oxygen delivery versus enhanced manual oxygen delivery There may be no clear difference in time (%) in the desired SpO2 range between infants who receive automated oxygen delivery and infants who receive manual oxygen delivery (MD 7.28%, 95% CI -1.63 to 16.19; I2 = 0%; 2 studies, 19 infants; low-certainty evidence). No studies assessed in-hospital mortality, severe ROP, or neurodevelopmental outcomes. Revised closed-loop automatic control algorithm (CLACfast) versus original closed-loop automatic control algorithm (CLACslow) CLACfast allowed up to 120 automated adjustments per hour, whereas CLACslow allowed up to 20 automated adjustments per hour. CLACfast may result in little or no difference in time (%) in the desired SpO2 range compared to CLACslow (MD 3.00%, 95% CI -3.99 to 9.99; 1 study, 19 infants; low-certainty evidence). No studies assessed in-hospital mortality, severe ROP, or neurodevelopmental outcomes. OxyGenie compared to CLiO2 Data from a single small study were presented as medians and interquartile ranges and were not suitable for meta-analysis.

AUTHORS' CONCLUSIONS

Automated oxygen delivery compared to routine manual oxygen delivery probably increases time in desired SpO2 ranges in preterm infants on respiratory support. However, it is unclear whether this translates into important clinical benefits. The evidence on clinical outcomes such as severe retinopathy of prematurity are of low certainty, with little or no differences between groups. There is insufficient evidence to reach any firm conclusions on the effectiveness of automated oxygen delivery compared to enhanced manual oxygen delivery or CLACfast compared to CLACslow. Future studies should include important short- and long-term clinical outcomes such as mortality, severe ROP, bronchopulmonary dysplasia/chronic lung disease, intraventricular haemorrhage, periventricular leukomalacia, patent ductus arteriosus, necrotising enterocolitis, and long-term neurodevelopmental outcomes. The ideal study design for this evaluation is a parallel-group randomised controlled trial. Studies should clearly describe staffing levels, especially in the manual arm, to enable an assessment of reproducibility according to resources in various settings. The data of the 13 ongoing studies, when made available, may change our conclusions, including the implications for practice and research.

Measuring Oxygenation in Newborn Infants with Targeted Oxygen Ranges (MONITOR): a randomised crossover pilot study

OBJECTIVE

The Neonatal Oxygenation Prospective Meta-analysis (NeOProM) Collaboration showed that high (91-95%) versus low (85-89%) SpO2 targets reduced mortality. Trials of higher targets are needed to determine whether any more survival advantage may be gained. This pilot study explored the achieved oxygenation patterns observed when targeting SpO2 92-97% to facilitate the design of future trials.

DESIGN

Single-centre prospective randomised crossover pilot study. Manual FiO2 adjustment. Study time 12 hours per infant. 6 hours targeting SpO2 90-95% and 6 hours targeting SpO2 92-97%.

PATIENTS

Twenty preterm infants born <29 weeks' gestation, greater than 48 hours old, receiving supplemental oxygen.

OUTCOMES

Primary outcome was percentage time with SpO2 above 97% and below 90%. Pre-defined secondary outcomes included percentage time spent within, above or below transcutaneous PO2 (TcPO2) 6.7-10.7 kPa (50-80 mm Hg). Comparisons were made using paired-samples t-test (2-tailed).

RESULTS

With SpO2 target 92-97% versus 90-95%, the mean (IQR) percentage time above SpO2 97% was 11.3% (2.7-20.9) versus 7.8% (1.7-13.9), p=0.02. Percentage time with SpO2 <90% was 13.1% (6.7-19.1) versus 17.9% (11.1-22.4), p=0.003. Percentage time with SpO2 <80% was 1% (0.1-1.4) versus 1.6% (0.4-2.6), p=0.119. Percentage time with TcPO2 <6.7 kPa (50 mm Hg) was 49.6% (30.2-66.0) versus 55% (34.3-73.5), p=0.63. Percentage time above TcPO2 10.7 kPa (80 mm Hg) was 1.4% (0-1.4) versus 1.8% (0-0), p=0.746.

CONCLUSIONS

Targeting SpO2 92-97% produced a right shift in SpO2 and TcPO2 distribution, with reduced time at SpO2 <90% and increased time at SpO2 >97%, without increasing time with TcPO2 >10.7 kPa (80 mm Hg). Clinical trials targeting this higher SpO2 range could be conducted without significant hyperoxic exposure.

TRIAL REGISTRATION NUMBER

NCT03360292.

Early neurodevelopmental follow-up in the NICHD neonatal research network: Advancing neonatal care and outcomes, opportunities for the future

At the inception of the Eunice Kennedy Shriver National Institute of Child Health and Development Neonatal Research Network (NRN), provision of care for extremely preterm (EPT) infants was considered experimental. The NRN Follow-up Study Group, initiated in 1993, developed infrastructure with certification processes and standards, allowing the NRN to assess 2-year outcomes for EPT and to provide important metrics for randomized clinical trials. This chapter will review the NRN Follow-up Study Group's contributions to understanding factors related to improved neurodevelopmental, behavioral, and social-emotional outcomes of EPT infants. We will also discuss follow up challenges, including reassessing which outcomes are most meaningful for parents and investigators. Finally, we will explore how outcome studies have informed clinical decisions and ethical considerations, given limitations of prediction of complex later childhood outcomes from early neurodevelopmental findings.

Translational Research in Retinopathy of Prematurity: From Bedside to Bench and Back Again

Retinopathy of prematurity (ROP), a vascular proliferative disease affecting preterm infants, is a leading cause of childhood blindness. Various studies have investigated the pathogenesis of ROP. Clinical experience indicates that oxygen levels are strongly correlated with ROP development, which led to the development of oxygen-induced retinopathy (OIR) as an animal model of ROP. OIR has been used extensively to investigate the molecular mechanisms underlying ROP and to evaluate the efficacy of new drug candidates. Large clinical trials have demonstrated the efficacy of anti-vascular endothelial growth factor (VEGF) agents to treat ROP, and anti-VEGF therapy is presently becoming the first-line treatment worldwide. Anti-VEGF therapy has advantages over conventional treatments, including being minimally invasive with a low risk of refractive error. However, long-term safety concerns and the risk of late recurrence limit this treatment. There is an unmet medical need for novel ROP therapies, which need to be addressed by safe and minimally invasive therapies. The recent progress in biotechnology has contributed greatly to translational research. In this review, we outline how basic ROP research has evolved with clinical experience and the subsequent emergence of new drugs. We discuss previous and ongoing trials and present the candidate molecules expected to become novel targets.

Risk Calculator for Retinopathy of Prematurity Requiring Treatment

Importance: Vascular delay that occurs early in the development of retinopathy of prematurity (ROP) is a risk factor that can be compensated by ensuring a good rate of retinal vascularization to avoid ROP that requires treatment. Background: The objective of the present study was to determine the association between ROP that requires treatment and risk factors such as the extent of the temporal avascular area of the retina and the number of days of mechanical ventilation (MV). Design: Observational retrospective case-control study. Participants: Two hundred and twenty-eight premature newborns included in the screening protocol for retinopathy of prematurity. Methods: Subjects underwent retinal examination in the 4 and 6th postnatal weeks. Main Outcome Measures: The temporal avascular area was measured in disc diameters (DD), while the MV time was measured in days of treatment. Results: Patients with a longer MV time had a higher risk of treatment (R ²: 24.7, p < 0.0001; increase in risk of 8.1% for each additional day), as did those who showed greater avascular area (R ²: 24.7, p < 0.0001; increase in risk of 111% for each additional DD). An online calculator system and a table are presented for calculating the risk of ROP requiring treatment as a function of these two risk factors. Conclusions and Relevance: The temporal avascular area of the retina and MV time must be taken into account in the first examination of the newborn to predict the need for ROP treatment.

Validation of an IGF1 Screening Method for Retinopathy of Pre-maturity

Retinopathy of pre-maturity (ROP) is a retinal disease that causes arrest of vascularization of the retina and can result in retinal detachment and blindness. Current screening protocols may not be sufficiently accurate to identify all at-risk patients. The aim of this study is to validate a method for improved identification of newborns at risk of ROP. We conducted a prospective clinical trial of pre-term newborns <32 weeks of gestation and/or <1,500 g birth weight during a 6-year period in a tertiary care hospital. We applied our new method based on measurement of insulin-like growth factor 1 (IGF1) levels at 3 weeks of age and the presence of sepsis during the first 3 weeks of life. Our screening protocol allowed exclusion of 121 (79.1%) patients for whom American Academy of Pediatrics (AAP) guidelines recommended screening, had a negative predictive value of 100%, and correctly identified all patients with ROP. Following retrospective assessment of our data based on these findings, we propose further restriction of the current AAP indications for screening to <1,100 g and <28 weeks of gestation in order to improve diagnostic efficacy while ensuring optimal use of restriction of human and material resources.

Principles of pulse oximetry and its clinical application in neonatal medicine

Pulse oximetry is one of the most commonly used monitoring devices in clinical medicine. It was first introduced to neonatal medicine in the mid-1980s to monitor oxygenation and guide therapy, and it is now used widely in the delivery room during resuscitation. More recently, it is utilized to screen for congenital heart disease. Pulse oximetry is based on the variation in the ratio of the light absorbances of tissues during systole and diastole. It has become the mainstay of non-invasive continuous oxygen monitoring but with a wide variation in clinical practices and without good research evidence. This article provides a brief historical overview of pulse oximetry development, its principles, advantages and limitations, and the clinical applications in neonatal medicine.

D-Penicillamine for preventing retinopathy of prematurity in preterm infants

BACKGROUND

The rate of retinopathy of prematurity (ROP) in moderately premature infants has decreased dramatically with improved care in the neonatal intensive care unit. A low rate of this disorder was unexpectedly observed among infants treated with intravenous D-penicillamine to prevent hyperbilirubinaemia. This observation led to the investigation of its use, both enterally as well as intravenously, to prevent ROP.

OBJECTIVES

To determine the effect of prophylactic administration of D-penicillamine on the incidence of acute ROP or severe ROP and other morbidities in preterm infants.

SEARCH METHODS

We used the Cochrane Neonatal Review Group search strategy. Two review authors independently searched multiple electronic databases, previous reviews including cross references, abstracts, conference/symposia proceedings, and expert informants. We updated the search on November 27, 2012.

SELECTION CRITERIA

We included randomised or quasi-randomised controlled trials if they administered D-penicillamine and compared it with no treatment or placebo to premature infants and reported on the outcome of ROP.

DATA COLLECTION AND ANALYSIS

We used the criteria and standard methods of the Cochrane Neonatal Review Group to assess the methodological quality of the included trials. One review author examined trials for validity. A second review author checked validity and they reached consensus on the final data before entry into this review. We used the standards of the Neonatal Cochrane Review Group to analyse data.

MAIN RESULTS

Three randomised trials met the inclusion criteria. The meta-analysis showed no significant differences in the risk of any stage ROP (typical risk ratio (RR) 0.32, 95% confidence interval (CI) 0.03 to 3.70), severe ROP (typical RR 0.38, 95% CI 0.03 to 4.26) or death (typical RR 0.95, 95% CI 0.68 to 1.32) in all treated infants. When the subgroup of infants under 1500 g birth weight was examined, the results were similar. No side effects were reported, and follow-up at one year revealed no significant differences in spasticity or developmental delay.

AUTHORS' CONCLUSIONS

Administration of prophylactic D-penicillamine in preterm infants does not prevent acute or severe ROP, death or neurodevelopmental delay. D-penicillamine cannot be recommended for the prevention of ROP based on the available evidence.

Phytochemicals in ocular health: Therapeutic potential and delivery challenges

Diabetic retinopathy (DR) and age-related macular degeneration (AMD) are the leading causes of blindness in adults. The impact of these conditions on the quality of life is increasing in significance with a rise in life expectancy. The role of hyperglycemia, oxidative stress and inflammatory responses in the development and/or progression of DR and AMD, and several other sight threatening ocular diseases, is well established. In proliferative retinopathy, signals sent by the retina for nourishment, triggers the growth of fragile and abnormal blood vessels. Changes in ocular pressure may lead to rupture of these blood vessels causing severe vision problems. Recent in vitro and preclinical studies demonstrate that certain phytochemicals possessing potent antioxidant and anti-inflammatory activity and ocular blood flow enhancing properties may be very useful in the treatment of, or as a prophylactic measure for, DR and AMD. Apart from these properties they have also been investigated for their anti-bacterial, hormonal, enzyme stimulation, and anti-angiogenic activities. The attractive aspect of these potential therapeutic candidates is that they can act on multiple pathways identified in the etiology of DR, AMD, cataract and other ocular diseases. However, results from clinical trials have been somewhat ambiguous, raising questions about the concentrations of these bioflavonoids achieved in the neural retina following oral administration. Unfortunately, as of date, an efficient noninvasive means to deliver therapeutic agents/candidates to the back-of-the eye is still not available. This review examines some of these promising natural agents and discusses the challenges encountered in delivering them to the posterior segment ocular tissues through the oral route.

Serum fructosamine and retinopathy of prematurity

OBJECTIVE

To determine whether serum fructosamine which is a good marker for detecting hyperglycemia during the previous 2 to 3 wk in infants could predict the development of retinopathy of prematurity in very low birth weight infants.

METHODS

One hundred sixty seven premature infants who had a birth weight of < 1500 g and a gestational age of less than 32 wk were investigated in the present study. Blood glucose was measured at the bedside and infants were recorded as hyperglycemic if their mean blood glucose levels were higher than 150 mg/dL. Serum corrected fructosamine level was obtained from the cord blood at birth and after the first month of life. The infants' eyes were examined by ophthalmologists to detect retinopathy of prematurity at the gestational age of 32 wk or at four wk after birth, whichever came first.

RESULTS

Corrected fructosamine was 319.6 ± 59.6 and 272.8 ± 50.6 mmol/l for group 1 on 1(st) and 30(th) day respectively; 320 ± 61.7 and 268.2 ± 47.3 mmol/l for groups 2 + 3 on 1(st) and 30(th) day respectively which did not differ between groups (p = 0.766 and p = 0.665), whereas duration of hyperglycemia was 1.69 ± 1.1 day in group 1 compared with 3.05 ± 2.4 day in groups 2 + 3 which was significantly different (p = 0.019). The multivariate regression analysis indicated that the duration of hyperglycemia in days was significantly correlated with the development of retinopathy of prematurity (OR 3.26; 95% CI 1.09-9.80; p = 0.035).

CONCLUSIONS

Although the duration of hyperglycemia may contribute to the development of retinopathy of prematurity, serum corrected fructosamine does not have a good predictive value in developing retinopathy of prematurity in very-low-birth-weight (VLBW) infants.

Serum levels of IGF1 are a useful predictor of retinopathy of prematurity

OBJECTIVE

To ascertain whether insulin-like growth factor 1 (IGF1) is associated with retinopathy of prematurity (ROP) and is a useful predictor of the disease. Although its aetiopathogenesis is multifactorial, development of the disease appears to be related to a deficiency in IGF1, a hormone that acts together with vascular endothelial growth factor in the normal angiogenesis in the retina.

DESIGN

Prospective study for a 30-month period.

PARTICIPANTS

A total of 74 premature newborn babies, of less than 1500 g and/or 32 weeks' gestational age or less.

TESTING

To determine the development and severity of ROP.

MAIN OUTCOME MEASURES

Serum levels of IGF1 were measured once a week from birth until 40 weeks corrected gestational age in each subject.

RESULTS

Of our subjects, 32.4% developed some form of ROP, and all those ROP patients had the following characteristics at birth (median +/- standard deviation scores): low weight (1098 +/- 188 vs. 1393 +/- 285 g), short length (36.74 +/- 1.77 vs. 38.89 +/- 3.08 cm), small cranial perimeter (26.03 +/- 1.74 vs. 27.93 +/- 1.81 cm) and young gestational age (29.7 +/- 1.78 vs. 31.3 +/- 1.79 weeks) (p < 0.05). Other factors previously associated with ROP that were also observed with statistically significant frequency in our ROP patients were bronchopulmonary dysplasia, intracranial haemorrhage, the need for erythrocyte transfusion or treatment with erythropoietin and sepsis (all p < 0.05). Levels of IGF1 at the 3rd week post-partum, independent of gestational age at birth, were clearly lower in the group who developed ROP (29.13 vs. 43.16 ng/mL, p < 0.05). A value of 30 ng/mL of IGF1 in the third week post-partum was found to have a 90% sensitivity in the diagnosis of ROP. A rapid rise in IGF1 levels between the 3rd and 5th weeks appeared to be related to the development of a higher stage of ROP.

CONCLUSION

Determination of IGF1 serum levels in the 3rd week post-partum, independent of gestational age at birth, provides a sufficient and reliable prognostic tool and allows the identification of a group of patients at high risk of developing the disease.

Oxygen supply and consumption in the retina: implications for studies of retinopathy of prematurity

A disrupted oxygen environment in the retina of severely premature neonates is thought to be a key factor in the development of retinopathy of prematurity (ROP). This review describes our understanding of intraretinal oxygen distribution and consumption in a range of animal models, including species with naturally avascular retinas and models of induced occlusion of the retinal vasculature. The influence of graded systemic hyperoxia on retinal oxygenation is also discussed along with modulation of retinal oxygen metabolism. The differences in retinal oxygenation between developing and mature retinas are also described. Comparisons are made with studies in the monkey retina in order to assess possible similarities in behaviour between rat and human retinas. Pathogenesis mechanism and possible intervention strategies during the diseased processes in ROP are proposed based on our current knowledge.

Restricted versus liberal oxygen exposure for preventing morbidity and mortality in preterm or low birth weight infants

BACKGROUND

While the use of supplemental oxygen has a long history in neonatal care, resulting in both significant health care benefits and harms, uncertainty remains as to the most appropriate range to target blood oxygen levels in preterm and low birth weight infants. Potential benefits of higher oxygen targeting may include more stable sleep patterns and improved long-term growth and development. However, there may be significant deleterious pulmonary effects and health service use implications resulting from such a policy.

OBJECTIVES

To determine whether targeting ambient oxygen concentration to achieve a lower vs. higher blood oxygen range, or administering restricted vs. liberal supplemental oxygen, effects mortality, retinopathy of prematurity, lung function, growth or development in preterm or low birth weight infants.

SEARCH STRATEGY

The standard search strategy of the Neonatal Review Group was used. An additional literature search was conducted of the MEDLINE and CINAHL databases in order to locate any trials in addition to those provided by the Cochrane Controlled Trials Register (CENTRAL/CCTR). Search updated to week two July 2008.

SELECTION CRITERIA

All trials in preterm or low birth weight infants utilising random or quasi-random patient allocation in which ambient oxygen concentrations were targeted to achieve a lower vs. higher blood oxygen range, or restricted vs. liberal oxygen was administered were eligible for inclusion.

DATA COLLECTION AND ANALYSIS

The methodological quality of the eligible trials was assessed independently by each review author for the degree of selection, performance, attrition and detection bias. Data were extracted and reviewed independently by the each author. Data analysis was conducted according to the standards of the Cochrane Neonatal Review Group.

MAIN RESULTS

In the meta-analysis of the five trials included in this review, the restriction of oxygen significantly reduced the incidence and severity of retinopathy of prematurity without unduly increasing death rates The one prospective, multicenter, double-blind, randomized trial investigating lower vs. higher blood oxygen levels from 32 weeks postmenstrual age showed no significant differences in the rates of ROP, mortality or growth and development between the two groups. However, this study did show increased rates of chronic lung disease and home oxygen use.

AUTHORS' CONCLUSIONS

The results of this systematic review confirm that (the now historical) policy of unrestricted, unmonitored oxygen therapy has potential harms without clear benefits. However, the question of what is the optimal target range for maintaining blood oxygen levels in preterm/LBW infants was not answered by the data available for inclusion in this review.

Vascular endothelial growth factor in eye disease

Collectively, angiogenic ocular conditions represent the leading cause of irreversible vision loss in developed countries. In the US, for example, retinopathy of prematurity, diabetic retinopathy and age-related macular degeneration are the principal causes of blindness in the infant, working age and elderly populations, respectively. Evidence suggests that vascular endothelial growth factor (VEGF), a 40kDa dimeric glycoprotein, promotes angiogenesis in each of these conditions, making it a highly significant therapeutic target. However, VEGF is pleiotropic, affecting a broad spectrum of endothelial, neuronal and glial behaviors, and confounding the validity of anti-VEGF strategies, particularly under chronic disease conditions. In fact, among other functions VEGF can influence cell proliferation, cell migration, proteolysis, cell survival and vessel permeability in a wide variety of biological contexts. This article will describe the roles played by VEGF in the pathogenesis of retinopathy of prematurity, diabetic retinopathy and age-related macular degeneration. The potential disadvantages of inhibiting VEGF will be discussed, as will the rationales for targeting other VEGF-related modulators of angiogenesis.

Risk factors in the development of mild and severe retinopathy of prematurity

PURPOSE

To evaluate the risk factors in the development of mild and severe retinopathy of prematurity (ROP).

METHODS

All infants (n = 88) screened for ROP at a neonatal intensive care unit over a 2-year period with gestational age <or=34 weeks and follow-up of 43 weeks postconception were included. The findings were classified in accordance with the International Classification of Retinopathy of Prematurity. The study group was classified into three subgroups: group A included patients without retinopathy; group B included patients with stage 1 or 2 (mild-ROP); and group C included patients who progressed to moderate or severe stage 3 (severe-ROP) and were treated. A retrospective review of records was performed and statistical analysis of eight possible risk factors for ROP was evaluated by using logistic regression.

RESULTS

Logistic regression analysis showed birth weight (BW) (p=0.019) and respiratory distress syndrome (p = 0.029) as independent significant risk factors for the development of stage 1 and 2 ROP, with BW (p < 0.0001) as an independent significant risk factor for the progression to stage 3 ROP. Total volume of blood transfusion and duration of artificial ventilation were also found to be risk factors with high rates of stage 3 ROP. In group C, BW <or=1000 g (p = 0.0002) and gestational age <or=28 weeks (p < 0.0001) were significant risk factors associated with higher rates of ROP.

CONCLUSIONS

This study showed BW and respiratory distress syndrome as independent risk factors in the development of mild ROP and BW in the development of severe ROP.

Postnatal risk factors of retinopathy of prematurity

To investigate the postnatal risk factors of retinopathy of prematurity (ROP), we analysed demographic and clinical data abstracted from the medical records of 425 premature babies who were examined for ROP between January 1994 and December 1998 at Asan Medical Centre, Seoul, Korea. ROP developed in 20.7% of the cases studied. A gestational age (GA) of < or = 28 weeks and birthweight (BW) of < or = 1000 g were the most significant risk factors. Ventilator care for > or = 48 h, apnoea, and use of surfactant independently increased the incidence of ROP. Furthermore, frequent apnoeic attacks increased the progression of pre-threshold ROP to threshold ROP. Therefore, as well as GA and BW, apnoea, prolonged use of a ventilator, and surfactant therapy are significant independent risk factors for ROP. In addition, apnoea may not only increase the risk of developing ROP, but may also worsen pre-existing ROP.

Retinopathy of prematurity and pulse oximetry: a national survey of recent practices

OBJECTIVE

To determine if practices related to the use of pulse oximetry in the first 2 weeks following birth and after 2 weeks of age have a relationship to the rate of retinopathy of prematurity (ROP) and retinal ablation surgery in infants < or =1500 g.

STUDY DESIGN

A questionnaire was mailed in July 2001 to 318 neonatal intensive care units (NICUs) in the United States and information was collected regarding SpO2 guidelines and the rate of both severe ROP and retinal ablation surgery.

RESULTS

A total of 142 surveys were returned (45%). In all, 87% of the NICUs had SpO2 guidelines, and 60% of these centers maintained a different range of SpO2 for infants < or = or >2 weeks of age. The range of SpO2 was 82 to 100% with an average minimum (min) and maximum (max) of 89 and 95%, respectively. In the NICUs with an SpO2 max of >98% in the first 2 weeks following birth, the rate of retinal ablation surgery was 5.5 vs 3% in those units with a max SpO2 >98% (p<0.05). After 2 weeks of age, the rate of retinal ablation surgery was 3.3% when max SpO2 was >92 vs 1.3% when the max SpO2 was < or =92% (p<0.00001). The rate of > or =stage 3 ROP after 2 weeks of age was 5.5% when max SpO2 was >92 vs 2.4% when max SpO2 was < or =92% (p<0.0005).

CONCLUSION

NICUs in the US today have a wide range of SpO2 guidelines. The results of this survey show a "gradient of risk" towards less retinal ablation surgery when the max SpO2 is <98% in the first 2 weeks following birth (p<0.05). There was a statistically significant lower rate of > or =stage 3 ROP and retinal ablation surgery when the max SpO2 was < or =92% after the first 2 weeks of age. A randomized, controlled trial is needed to establish a safe upper limit of SpO2 in the premature infant at risk for developing ROP.

Hyperglycemia and retinopathy of prematurity in very low birth weight infants

OBJECTIVE

Retinopathy of prematurity (ROP) remains a leading cause of morbidity in the very low-birth-weight (VLBW) infant. This study investigates a possible association between serum/blood glucose and the development of ROP.

METHODS

A retrospective case-control study of all infants born between 1992 and 1997 at the Johns Hopkins Hospital with birth weights less than 1000 g who developed Stage 3 or 4 ROP was conducted. Controls either had Stage 1 ROP or no eye disease and were matched 2:1 with ROP patients for gestational age, birth weight and year of birth. Odds ratios (ORs) of ROP were calculated for multiple exposures over the first month after birth, including oxygen concentration (FiO(2)), blood glucose levels, vitamin E, mean airway pressure and mean blood pressure.

RESULTS

In a simple logistic regression analysis, we found an increased ROP risk for: (1) each 10 mg/dl increase of mean glucose (OR 1.96; 95% CI 1.13 to 3.42), (2) each 1% increase of mean FiO(2) (OR 1.06; 95% CI 1.004 to 1.13), (3) history of dopamine infusion (OR 5.4; 95% CI 1.16 to 25.2) and (4) intraventricular hemorrhage Grade 3 or 4 (OR 7.3; 95% CI 1.53 to 34.7). Using a multiple regression model, we found an increased ROP risk for each 10 mg/dl increase of mean glucose (OR 2.7; 95% CI 1.003 to 7.27). Each IU/kg/day of vitamin E supplementation reduced ROP risk (OR 0.37; 95% CI 0.16-0.86).

CONCLUSION

In this study, we could demonstrate that glucose levels in the first month of life are associated with the development of ROP. Further studies have to determine if this association is causal or if hyperglycemia is just an expression of severity of illness.

Oxygen monitoring in preterm babies: too high, too low?

A small randomised trial in 1952 showed that excess oxygen use might well be causing a major epidemic of retinal blindness in preterm babies. That single study of just 65 babies was enough to throw doubt on a longstanding treatment strategy of oxygen therapy and highlighted just how powerful a tool the randomised controlled trial could be. Confirmatory evidence from a co-operative trial 4 years later involving 212 babies banished all residual doubt and we should reproach ourselves that we have still not learnt after 50 years how to optimise oxygen delivery to the preterm baby, making further use of this powerful research tool. Two well-conducted trials have recently shown that avoiding subclinical hypoxaemia (a fractional SaO(2) of less than 92%) in babies more than a month old does nothing to improve later growth or development. It is now time the same question was asked of babies less than a month old. This is particularly important in babies of less than 28 weeks' gestation, who currently remain at serious risk of chronic lung disease and permanent retinal damage.

Giving small babies oxygen: 50 years of uncertainty

A small landmark trial in 1952 showed that excess oxygen use might well be causing a major epidemic of retinal blindness in preterm babies. That a single study of just 65 babies was enough to throw doubt on a long-standing treatment strategy revealed just how powerful a tool the randomized controlled trial could be. Confirmatory evidence from a cooperative trial involving a further 212 babies banished all residual doubt just 4 years later, and it remains a major reproach that we have still not learnt, after 50 years, how to optimize the delivery of oxygen to the preterm baby with further help from this powerful tool. Two well-conducted trials have recently shown that avoiding subclinical hypoxaemia (fractional SaO(2)<92%) in babies more than a month old does nothing to improve later growth or development. It is now time the same question was asked of babies less than a month old, because we might reduce their need for ventilatory support. This is particularly important in babies of less than 28 weeks' gestation, who remain, currently, at serious risk of chronic lung disease and permanent retinal scarring.

Retinopathy of prematurity outcome in infants with prethreshold retinopathy of prematurity and oxygen saturation >94% in room air: the high oxygen percentage in retinopathy of prematurity study

OBJECTIVES

To determine the rate of progression from prethreshold to threshold retinopathy of prematurity (ROP) in infants excluded from Supplemental Therapeutic Oxygen for Prethreshold Retinopathy of Prematurity (STOP-ROP) because their median arterial oxygen saturation by pulse oximetry (SpO2) values were >94% in room air at the time of prethreshold diagnosis and to compare them with infants who were enrolled in STOP-ROP and had median SpO2 < or =94% in room air.

METHODS

Fifteen of the 30 centers that participated in STOP-ROP elected to participate in the High Oxygen Percentage in Retinopathy of Prematurity study (HOPE-ROP) from January 1996 to March 1999. Infants were followed prospectively from the time prethreshold ROP was diagnosed until ROP either progressed to threshold in at least 1 study eye (adverse outcome) or resolved (favorable outcome).

RESULTS

A total of 136 HOPE-ROP infants were compared with 229 STOP-ROP infants enrolled during the same time period from the same 15 hospitals. HOPE-ROP infants were of greater gestational age at birth (26.2 +/- 1.8 vs 25.2 +/- 1.4 weeks) and greater postmenstrual age at the time of prethreshold ROP diagnosis (36.7 +/- 2.5 vs 35.4 +/- 2.5 weeks). HOPE-ROP infants progressed to threshold ROP 25% of the time compared with 46% of STOP-ROP infants. After gestational age, race, postmenstrual age at prethreshold diagnosis, zone 1 disease, and plus disease at prethreshold diagnosis were controlled for, logistic regression analysis showed that HOPE-ROP infants progressed from prethreshold to threshold ROP less often than STOP-ROP infants (odds ratio: 0.607; 95% confidence interval: 0.359-1.026).

CONCLUSIONS

The mechanisms that result in better ROP outcome for HOPE-ROP versus STOP-ROP are not fully understood. It seems that an infant's SpO2 value at the time of prethreshold diagnosis is a prognostic indicator for which infants may progress to severe ROP. When other known prognostic indicators are factored in, the SpO2 is of borderline significance.

Restricted versus liberal oxygen exposure for preventing morbidity and mortality in preterm or low birth weight infants

BACKGROUND

This section is under preparation and will be included in the next issue.

OBJECTIVES

In preterm or low birth weight infants, does targeting ambient oxygen concentration to achieve a lower versus higher blood oxygen range, or administering restricted versus liberal supplemental oxygen, influence mortality, retinopathy of prematurity, lung function, growth or development?

SEARCH STRATEGY

The standard search strategy of the Neonatal Review Group was used. An additional literature search was conducted of the MEDLINE, EMBASE, and CINAHL databases in order to locate any trials in addition to those provided by the Cochrane Controlled Trials Register (CENTRAL/CCTR).

SELECTION CRITERIA

All trials in preterm or low birth weight infants utilising random or quasi-random patient allocation, in which ambient oxygen concentrations were targeted to achieve a lower versus higher blood oxygen range, or restricted versus liberal oxygen was administered, were eligible for inclusion.

DATA COLLECTION AND ANALYSIS

The methodological quality of the eligible trials was assessed independently by each author for the degree selection, performance, attrition and detection bias. Data were extracted and reviewed independently by the each author. Data analysis was conducted according to the standards of the Cochrane Neonatal Review Group.

MAIN RESULTS

The restriction of oxygen significantly reduced the incidence and severity of retinopathy of prematurity without unduly increasing death rates in the meta-analysis of the five trials included in this review. The one trial that specifically addressed the question of lower versus higher PaO2 found no effect on death, but did not report (in sufficient detail to warrant inclusion) the effect of this intervention on eye or other outcomes. The effects of either of these oxygen administration policies on other clinically meaningful outcomes including chronic lung disease and long term growth, neurodevelopment, lung or visual function were not reported in any of the available trials.

REVIEWER'S CONCLUSIONS

The results of this meta-analysis confirm the commonly held view of today's clinicians that a policy of unrestricted, unmonitored oxygen therapy has potential harms, without clear benefits. However, the question of what is the optimal target range for maintaining blood oxygen levels in preterm/LBW infants was not answered by the data available for inclusion in this review.

D-Penicillamine for preventing retinopathy of prematurity in preterm infants

BACKGROUND

This section is under preparation and will be included in the next issue.

OBJECTIVES

To answer the question: Among very low birth weight infants, what is the effect of prophylactic administration of d-penicillamine on the incidence of acute ROP or severe ROP, and side effects including death?

SEARCH STRATEGY

Searches were made of multiple electronic databases, previous reviews including cross references, abstracts, conference/symposia proceedings, and expert informants.

SELECTION CRITERIA

Randomized or quasi-randomized controlled trials that administered d-penicillamine to infants less than 2000g birth weight within the day following birth were considered relevant to this review. Additional case series were examined for potential side effects.

DATA COLLECTION AND ANALYSIS

Data on clinical outcomes were excerpted by 3 reviewers independently, and consensus reached. Data analysis was conducted according to the standards of the Neonatal Cochrane Review Group.

MAIN RESULTS

Two randomized trials on the effects on ROP were identified. When combined, they showed a significantly lower incidence of acute ROP in the treated infants, relative risk of 0.09, 95% CI [0.01,0.71]. Severe stages of ROP could not be analyzed. There was no effect on death rates, relative risk 0.99 95% CI [0.70,1.39]. No side effects were reported, and follow up at one year revealed no significant differences in spasticity or developmental delay, although there were more rehospitalizations among the controls. In other reports of using d-penicillamine in over 140 infants for hyperbilirubinemia, skin rashes were reported in 2 infants and one had vomiting that may have been related.

REVIEWER'S CONCLUSIONS

D-penicillamine is unlikely to affect survival, and may reduce the incidence of acute ROP among survivors. Studies to date justify further investigation of this drug in a broader population; careful attention to possible side effects is needed.

The decreasing incidence and severity of retinopathy of prematurity

PURPOSE

We sought to determine whether the incidence of retinopathy of prematurity (ROP) at our institution has changed since the Cryo-ROP recruitment period 10 years ago.

METHODS

We determined the incidences of threshold ROP, prethreshold ROP, less-than-prethreshold ROP, and no disease for each of 3 birth weight classes (<750 g, 750 to 999 g, and 1000 to 1250 g) of infants born between July 1, 1995, and June 30, 1996, and cared for in the Vanderbilt Neonatal Intensive Care Unit. We then compared these with the rates from our institution during the Cryo-ROP study recruitment period (January 1, 1986, to November 30, 1987).

RESULTS

The current incidence and severity of ROP have decreased substantially overall and for each weight group compared with the 1986-87 incidence (P < .001, Cochran-Mantel-Haenszel test). The incidence of "any ROP" decreased by 27% for infants with birth weights less than 750 g, by 51% for infants 750 to 999 g, and by 71% for infants 1000 to 1250 g. The incidence of "prethreshold or greater ROP" decreased by 70% for the 750 to 999 g and 77% for the 1000 to 1250 g weight groups. Although the decrease in "prethreshold or greater ROP" was not as dramatic (25%) for the infants less than 750 g, only 1 infant (10%) progressed to threshold disease in this group, whereas 7 (47%) did in 1986-87. The incidence of threshold ROP decreased by 84% for infants less than 750 g and by 66% for infants 750 to 999 g. No infant with birthweight greater than 999 g progressed to threshold ROP.

CONCLUSIONS

The incidence of all levels of ROP has decreased substantially for all infants with birth weights less than 1251 g at Vanderbilt University Medical Center during the past decade. Putative factors responsible for this decrease may include surfactant use, continuous pulse oximetry, aggressive use of antenatal steroids, and improved neonatal nutritional support.

Therapeutic effect of liposomal superoxide dismutase in an animal model of retinopathy of prematurity

A newborn rat model of retinopathy of prematurity was used to test the hypothesis that a lack of superoxide dismutase contributes to the retinal vaso-attenuation seen during exposure of the animals to hyperoxic conditions. To determine the endogenous superoxide dismutase activity of the retina under hyperoxic conditions, litters of albino rats were placed in either constant 80% ambient oxygen (constant hyperoxia), or placed in 21% oxygen (room air) immediately after birth. Every other day, for 14 days, several rat pups were sacrificed and their retinas removed for the determination of total superoxide dismutase (SOD) activity and manganese-associated SOD activity. An attempt was made to increase retinal SOD activity by intraperitoneal administration of exogenous SOD encapsulated in polyethylene glycol-modified liposomes. Additional litters were exposed to the same oxygen treatments and supplemented twice daily with either liposome-encapsulated superoxide dismutase in saline or liposomes containing saline without SOD. Animals were sacrificed at various time points for the determination of total superoxide dismutase activity and computer-assisted analysis of vessel density and avascular area. Animals raised in an atmosphere of constant 80% oxygen had significantly reduced levels of retinal superoxide dismutase activity through 6 days of life when compared to their room air-raised littermates. At 6 days of age, daily supplementation with liposome-encapsulated SOD had significantly increased retinal superoxide dismutase activity and reduced oxygen-induced vaso-attenuation as evidenced by increased vessel density and decreased avascular area, when compared to littermates exposed to constant hyperoxia that received control liposomes. Superoxide dismutase had no adverse effects on any of the animals regardless of treatment. Tracing experiments demonstrated that liposomes entered the retina and were found in cells morphologically resembling microglia. Delivery of SOD to the retina via long-circulating liposomes proved beneficial, suggesting that restoration and/or supplementation of endogenous antioxidants in oxygen-damaged retinal tissue is a potentially valuable therapeutic strategy.

Therapeutic effect of liposomal superoxide dismutase in an animal model of retinopathy of prematurity

A newborn rat model of retinopathy of prematurity was used to test the hypothesis that a lack of superoxide dismutase contributes to the retinal vaso-attenuation seen during exposure of the animals to hyperoxic conditions. To determine the endogenous superoxide dismutase activity of the retina under hyperoxic conditions, litters of albino rats were placed in either constant 80% ambient oxygen (constant hyperoxia), or placed in 21% oxygen (room air) immediately after birth. Every other day, for 14 days, several rat pups were sacrificed and their retinas removed for the determination of total superoxide dismutase (SOD) activity and manganese-associated SOD activity. An attempt was made to increase retinal SOD activity by intraperitoneal administration of exogenous SOD encapsulated in polyethylene glycol-modified liposomes. Additional litters were exposed to the same oxygen treatments and supplemented twice daily with either liposome-encapsulated superoxide dismutase in saline or liposomes containing saline without SOD. Animals were sacrificed at various time points for the determination of total superoxide dismutase activity and computer-assisted analysis of vessel density and avascular area. Animals raised in an atmosphere of constant 80% oxygen had significantly reduced levels of retinal superoxide dismutase activity through 6 days of life when compared to their room air-raised littermates. At 6 days of age, daily supplementation with liposome-encapsulated SOD had significantly increased retinal superoxide dismutase activity and reduced oxygen-induced vaso-attenuation as evidenced by increased vessel density and decreased avascular area, when compared to littermates exposed to constant hyperoxia that received control liposomes. Superoxide dismutase had no adverse effects on any of the animals regardless of treatment. Tracing experiments demonstrated that liposomes entered the retina and were found in cells morphologically resembling microglia. Delivery of SOD to the retina via long-circulating liposomes proved beneficial, suggesting that restoration and/or supplementation of endogenous antioxidants in oxygen-damaged retinal tissue is a potentially valuable therapeutic strategy.

Retinopathy of prematurity--current diagnosis and management

Despite advances in ophthalmological care of premature infants, retinopathy of prematurity (ROP) remains a still unsolved problem for paediatricians as well as ophthalmologists. A survey of the current literature concerning drug therapy and surgical management as related to the different stages of ROP is given. The classification system for ROP according to the International Committee is presented as well as our screening policy in relation to the literature. The effectiveness in preventing severe cases of ROP and the toxicity of vitamin E supplementation in high-risk premature infants is still disputed and no recommendations can be given. Cryotherapy is recommended in symmetric cases of stage 3 + ROP. Nevertheless, quite a number of eyes still progress to more severe stages of ROP. Scleral buckling procedures and vitrectomy may lead to anatomical success in a few cases of retinal detachment, however, the visual outcome of such an operation is usually very poor despite reattachment of the central retina.

The progression of retinopathy of prematurity and fluctuation in blood gas tension

In this study, the relationship between the fluctuation in blood oxygen and carbon dioxide tension and the progression of acute retinopathy of prematurity (ROP) was evaluated. Eighteen extremely premature infants were selected on the basis of the following criteria: gestational age less than 26 weeks, oxygen supply or mechanical ventilation for more than 50 days, transcutaneous oxygen pressure (TcPO2) recorded almost once per hour, and arterial oxygen pressure (PaO2) and arterial carbon dioxide pressure (PaCO2) measured intermittently, for over 8 weeks after birth. All of these infants developed ROP, which ceased progressing in 7 infants (group I, stage 1 or 2 ROP, international classification), but advanced in 11 (group II, stage 3 or 3+). The fluctuations in TcPO2, PaO2, and PaCO2 are represented as coefficients of both variation (CV) and mean difference (D) in these two groups. The results demonstrate that both the CV and D values of TcPO2 are significantly elevated in group II infants compared with group I infants, in the first and second 3-weeks periods, and over the entire 9-week period after birth. The incidences of extreme hyperoxemia (TcPO2 > or = 100 mm Hg) and hypoxemia (TcPO2 < 30 mm Hg) in recorded TcPO2 time series show no significant differences between these two groups. We conclude that extremely premature infants with widely fluctuating arterial oxygen tension may have a greater chance of developing progressive ROP.

Current concepts in retinopathy of prematurity

Significant advances regarding understanding the etiology and treatment of retinopathy of prematurity have occurred in the 50 years since its discovery. Nevertheless, there is still a great deal to be learned. In spite of major technological advances in neonatal care, retinopathy of prematurity is a multi-factorial disease and probably cannot be completely prevented. Early intervention in the diagnosis and management of these infants has greatly improved their visual prognosis. Further studies may help pediatricians and neonatologists to understand and control associated risk factors. Ophthalmologists must continue to examine these patients early and follow them closely to control the associated treatable aspects of the disease, such as strabismus and amblyopia.

A cohort study of transcutaneous oxygen tension and the incidence and severity of retinopathy of prematurity

BACKGROUND

Retinopathy of prematurity is a disease affecting the blood vessels of the retina in premature infants that may result in scarring, retinal detachment, and loss of vision. An association between this condition and the exposure of premature infants to supplemental oxygen has been postulated, but the relation between retinopathy of prematurity and blood oxygen levels has not been defined. The purpose of this study of a cohort of preterm infants was to correlate the incidence and severity of retinopathy of prematurity with the duration of exposure to different ranges of oxygen tension as measured by transcutaneous monitoring (tcPO2).

METHODS

One hundred one premature infants (birth weight, 500 to 1300 g) requiring supplemental oxygen had continuous monitoring of tcPO2. The number of hours during which the tcPO2 was 80 mm Hg or higher was tabulated for each infant during the first four weeks of life.

RESULTS

There was a significant association between the amount of time that the tcPO2 was greater than or equal to 80 mm Hg and the incidence and severity of retinopathy of prematurity. The odds ratio for each 12-hour period in which the tcPO2 was greater than or equal to 80 mm Hg was 1.9 (95 percent confidence interval, 1.2 to 3.0) after adjustment for the following factors: birth weight less than or equal to 1300 g (odds ratio, 2.3 [95 percent confidence interval, 1.6 to 3.4]), five-minute Apgar score of 7 or less (odds ratio, 7.2 [95 percent confidence interval, 2.5 to 21]), and exposure to inspired oxygen at a concentration greater than or equal to 0.4 (odds ratio, 1.0 [95 percent confidence interval, 0.97 to 1.05]). The association was stronger for tcPO2 values of greater than or equal to 80 mm Hg occurring from the second through the fourth week of life; during this period, the adjusted odds ratio for a 12-hour period of such exposure was 3.1 (95 percent confidence interval, 1.6 to 6.1).

CONCLUSIONS

This study supports an association between the incidence and severity of retinopathy of prematurity and the duration of exposure to arterial oxygen levels of 80 mm Hg or higher, measured transcutaneously.

Regressed retinopathy of prematurity and its sequelae in children aged 5-10 years

Regressed retinopathy of prematurity (ROP) and its sequelae were studied in children born prematurely (less than 1501 g birth weight and/or less than 33 weeks gestational age) in Stockholm county during 1976-81. Through various searches of the records at the different eye departments and other sources in Stockholm county we found that 134 out of a total of 528 premature babies (25.4%) had needed ophthalmic care for different reasons. They were re-examined and reliable information on the fundus could be obtained for 105 of them. The frequency of regressed ROP was 45.5%. Severe forms with vitreoretinal scarring and retinal traction were seen in 9.7% of cases and moderate forms with pigmentary changes and/or vitreoretinal interphase changes in 35.8%. The sequelae of regressed ROP were mainly reduction of visual acuity and myopia. Children with a birth weight below 1000 g and a gestational age less than 30 weeks presented the highest rate of regressed ROP (68.5% and 61.9%) and ocular abnormalities.

Retinopathy of prematurity (ROP): optimal timing of clinical evaluation and standard procedures

The authors present the protocol currently used in their institution for initial and follow-up evaluation of infants at high risk for developing retinopathy of prematurity (ROP). After topical anesthesia and lid speculum insertion, the examination is carried out using an indirect binocular ophthalmoscope with a +20 or +28-diopter lens. Mydriasis is achieved by instilling one drop of 1% tropicamide, followed by one drop of 0.5% tropicamide + 2.5% phenylephrine 15 minutes later and after an additional 15 minute interval, another drop of 1% tropicamide. If mydriasis is insufficient after one hour, one drop of a 0.5% tropicamide-5.0% phenylephrine solution may be instilled. The initial examination is performed between the third and fourth weeks of life. If any areas of retinal immaturity are found, the examination is repeated every other week and, later, every three to four weeks, until vascularization has reached the ora serrata. Should any sign of ROP be present during the first examination, the patient is examined weekly or every other week depending on the severity of clinical findings.

Retinopathy of prematurity

ROP is a challenging disease of the decade of the 1980s. Answers, even partial answers, to many of its questions may provide information bearing on those same questions in other blinding vascular retinopathies, such as diabetes and sickle cell disease. Answers more clearly defining the role of oxygen, ventilation, antioxidants, blood transfusions, and a host of diseases of the premature infant will lead to better care of that infant. I have tried in this article to present the boundaries of the problem, a theory of its genesis and progression, and a review of the major issues to be confronted by the pediatric, ophthalmologic, and basic science communities through its recurrence today. I have tried to make it clear to the reader when I was so doing. I have used information liberally from studies both under way and in the planning stages to make the reader aware of what is being done, even if these have not yet reached fruition, for the field is a rapidly growing one. Finally, I have tried to point out directions that I believe clinical and experimental work should take on certain critical issues.