Retinopathy of prematurity: screening and optimal use of the ophthalmologist's time

Deep Learning Algorithm for Automated Diagnosis of Retinopathy of Prematurity Plus Disease

PURPOSE

This study describes the initial development of a deep learning algorithm, ROP.AI, to automatically diagnose retinopathy of prematurity (ROP) plus disease in fundal images.

METHODS

ROP.AI was trained using 6974 fundal images from Australasian image databases. Each image was given a diagnosis as part of real-world routine ROP screening and classified as normal or plus disease. The algorithm was trained using 80% of the images and validated against the remaining 20% within a hold-out test set. Performance in diagnosing plus disease was evaluated against an external set of 90 images. Performance in detecting pre-plus disease was also tested. As a screening tool, the algorithm's operating point was optimized for sensitivity and negative predictive value, and its performance reevaluated.

RESULTS

For plus disease diagnosis within the 20% hold-out test set, the algorithm achieved a 96.6% sensitivity, 98.0% specificity, and 97.3% ± 0.7% accuracy. Area under the receiver operating characteristic curve was 0.993. Within the independent test set, the algorithm achieved a 93.9% sensitivity, 80.7% specificity, and 95.8% negative predictive value. For detection of pre-plus and plus disease, the algorithm achieved 81.4% sensitivity, 80.7% specificity, and 80.7% negative predictive value. Following the identification of an optimized operating point, the algorithm diagnosed plus disease with a 97.0% sensitivity and 97.8% negative predictive value.

CONCLUSIONS

ROP.AI is a deep learning algorithm able to automatically diagnose ROP plus disease with high sensitivity and negative predictive value.

TRANSLATIONAL RELEVANCE

In the context of increasing global disease burden, future development may improve access to ROP diagnosis and care.

Auckland regional telemedicine retinopathy of prematurity screening network: A 10-year review

IMPORTANCE

Retinopathy of prematurity (ROP) is a potentially blinding condition affecting the retinae of premature infants. Effective screening is necessary for timely treatment.

BACKGROUND

The Auckland Regional Telemedicine ROP (ART-ROP) network, utilizes wide-field digital imaging for ROP screening. This study reviews the ART-ROP network.

DESIGN

Retrospective analysis of the ART-ROP database.

PARTICIPANTS

Files of infants in ART-ROP from 2006 to 2015.

METHODS

Data on infant demographics, ROP stage, treatment and outcome was collected.

MAIN OUTCOME MEASURES

The efficacy of ART-ROP in the management of ROP.

RESULTS

A review of 1181 infants across three neonatal intensive care units, was completed. Infants had a mean of four screening sessions with no infants who met ROP screening criteria being missed. Type 1 ROP was present in 83 infants, who had significantly lower average birth weight 786 ± 191 g compared to 1077 ± 285 g (P < .001), and gestational age 25.3 ± 1.7 weeks compared to 27.8 ± 2.2 weeks (P < .001) than the screened cohort. The number of infants requiring screening increased (R² = .7993), yet treatment rates decreased (R² = .9205) across the time period. Out-patient clinic follow-up was attended by 75.10% of infants screened and there was no missed ROP in those infants seen.

CONCLUSIONS AND RELEVANCE

ART-ROP solely uses wide-field digital imaging for ROP diagnosis, and management, including discharge, of infants. This detailed review of ART-ROP indicates an increase in screening demand, but a decrease in the rate of type 1 ROP. The ART-ROP telemedicine model demonstrates real potential to address workforce shortage in ROP screening.

Adequacy of published screening criteria for retinopathy of prematurity

BACKGROUND

Criteria for screening preterm infants for retinopathy of prematurity vary around the world. We aimed to analyse the efficacy of alternative screening criteria.

DESIGN

We collected retrospective data at a tertiary level neonatal nursery.

PARTICIPANTS

Our participants were 1007 babies, born between 1997 and 2011, at <32 weeks gestational age or <1500 g birth weight (as recommended by the National Health and Medical Research Council in 1996), who had completed follow-up to full retinal vascularization, with defined presence or absence of retinopathy of prematurity.

METHODS

We determined whether disease would be detected using an alternative Australian screening model (gestational age <30 weeks or birth weight <1250 g) or screening criteria utilized in developed countries with similar standards of neonatal care.

MAIN OUTCOME MEASURES

Detection of retinopathy of prematurity is our main outcome.

RESULTS

Using several of the alternative criteria, two neonates with clinically significant retinopathy of prematurity, one of whom required laser treatment to preserve sight, would not have been screened, and their disease may have gone undetected. Use of <30 weeks gestational age or <1500 g birth weight as the criteria would still have screened these infants but would have reduced the number of infants screened by 24.9%.

CONCLUSIONS

Some commonly utilized international screening criteria for retinopathy of prematurity may risk clinically significant cases being missed and others may screen babies unnecessarily. Alternative criteria should be considered and '<30 weeks gestational age and/or <1500 g birth weight' appears a viable option.

Retinopathy of prematurity: New developments bring concern and hope

Blindness from retinopathy of prematurity (ROP) in Australian and New Zealand is an uncommon event although 3% of <31 weeks gestation infants receive treatment for the disease. New world-wide estimates of the incidence of blindness from ROP are much higher than previously at 20 000 children annually. The impact of severe ROP can be reduced through good evidence-based care of very preterm infants and careful organisation of eye examinations and follow-up services. Recent oxygen saturation targeting trial results might mean the adoption of higher targets than formerly in very preterm infants and will require vigilance to ensure all eligible infants are examined appropriately. A true screening examination for acute ROP might involve non-opthalmologists obtaining photographic retinal images and remote reading of these. Although treatment with laser gives good outcomes, there is interest in intravitreal anti-vascular endothelial factor agents, but issues concerning the systemic safety and retinal results of such treatment are unresolved.

Visual impairment due to retinopathy of prematurity (ROP) in New Zealand: a 22-year review

AIM

To evaluate retinopathy of prematurity (ROP)-related visual impairment in New Zealand children.

METHODS

22-year retrospective review of medical records of children with moderate to severe visual impairment registered with the Blind and Low Vision Education Network New Zealand. The cohort was divided into two periods (1991-2004; 2005-2012) for analysis.

RESULTS

232 children with ROP were treated in the study period (109 in period 1, 123 in period 2). 36 children, 63.9% of whom were of male sex, were identified with subsequent significant visual impairment (27 in period 1, 9 in period 2). The incidence of new cases of visual impairment from ROP declined from 271.6 infants/100 000 live very preterm births per annum (period 1) to 146.1 per annum (period 2). Mean gestational age and mean birth weight were comparable between the two study periods. 75% of children with visual impairment from ROP received treatment for their condition (period 1, 74.1%; period 2, 77.8%) and modalities used changed significantly over time. The modal visual outcome overall was Snellen visual acuity <6/18-6/60 (55.6%) (period 1, 51.9%; period 2, 66.7%). The proportion of children with no light perception bilaterally decreased over time (period 1, 3.7%; period 2, 0%).

CONCLUSIONS

There has been a reduction in the incidence of infants with significant visual impairment from ROP over time in New Zealand, likely due to progress in clinical management of ROP. Our study suggests the current ROP screening criteria of <31 weeks' gestation or <1250 g are of sufficient breadth.

Incidence of retinopathy of prematurity requiring treatment in infants born greater than 30 weeks' gestation and with a birthweight greater than 1250 g from 1998 to 2002: a regional study

AIM

To ascertain the prevalence of significant Retinopathy of Prematurity (ROP) and ROP requiring treatment in infants born greater than 30 weeks gestation and with a birthweight greater than 1250 g, utilising the Neonatal Intensive Care Units' (NICUS) data collection from 1998 to 2002. Second, to determine whether infants delivered at more than 30 weeks gestation or with a birthweight greater than 1250 g require ROP screening.

METHODS

A review of the New South Wales and Australian Capital Territory NICUS data collection from 1998 to 2002 was performed. Infants of gestational age 31-33 weeks and with a birthweight greater than 1250 g were included. A review was performed of these infants to ascertain stage of ROP, threshold disease and treatment for ROP.

RESULTS

2292 infants were greater than 30 weeks and had a birthweight greater than 1250 g. Of these 1386 (60%) were not examined or died prior to eye examination. No ROP was noted in 888 of the 904 infants examined (98%), 13 infants had stage 1 (1.4%), five infants stage 2 (0.6%) and no infant had stage 3 ROP. No infant developed stage 3 ROP, required treatment for ROP or had threshold disease.

CONCLUSION

In this regional study of infants greater than 30 weeks gestation and with a birthweight greater than 1250 g, the prevalence of any ROP was low (2.0%). This study supports evidence from other studies that screening for ROP could be restricted, at least within our referral network, to infants less than 30 completed weeks and a birthweight less than 1250 g.

Variation in rates of severe retinopathy of prematurity among neonatal intensive care units in the Australian and New Zealand Neonatal Network

AIM

To analyse variations in rates of severe retinopathy of prematurity (ROP) among neonatal intensive care units (NICUs) in the Australian and New Zealand Neonatal Network (ANZNN), adjusting for sampling variability and for case mix.

METHODS

25 NICUs were included in the study of 2105 infants born at less than 29 weeks in 1998 and 1999, who survived to 36 weeks post-menstrual age and were examined for ROP. The observed NICU rates of severe ROP were adjusted for case mix using logistic regression on gestation, weight for gestational age and sex, and for sampling variability using shrinkage estimates. The corrected rate in the best 20% of NICUs was identified and NICU variations in rates were compared with those in 2000-1.

RESULTS

The overall (unadjusted) rate of severe ROP in the NICUs was 9.6% (interquartile range 5.4-12.8%). After adjusting for both case mix and sampling variability there remained significant variation among the NICUs. 20% of NICUs had a rate of severe ROP </=5.9%. Variation in rates among NICUs showed a similar pattern in both time periods. If the overall network rate was reduced to 5.9%, the 20th centile of the adjusted rates, there would be 79 fewer cases in a 2 year period, in contrast with 26 fewer if rates in the two units with excess rates improved to the average.

CONCLUSIONS

Considerable variation in rates of severe ROP among NICUs remained after adjustment for case mix and sampling variability. These data will facilitate investigation of potentially better practices associated with a reduced risk of severe ROP.

Prenatal risk factors for severe retinopathy of prematurity among very preterm infants of the Australian and New Zealand Neonatal Network

OBJECTIVE

To identify prenatal and perinatal risk factors for clinically severe (stage 3 or 4) retinopathy of prematurity (ROP).

METHODS

Data were collected prospectively as part of the ongoing Australian and New Zealand Neonatal Network audit of high-risk infants (birth weight of <1500 g or gestational age [GA] of <32 weeks) admitted to a level III neonatal unit in Australia or New Zealand. Prenatal and perinatal factors to 1 minute of age were examined for the subset of infants with GA of <29 weeks who survived to 36 weeks' postmenstrual age and were examined for ROP (n = 2105). The factors significantly associated with stage 3 or 4 ROP were entered into a multivariate logistic regression model.

RESULTS

Two-hundred three infants (9.6%) had stage 3 or more ROP. Prematurity was the dominant risk factor, with infants with GA of <25 weeks having 20 times greater odds of severe ROP than infants with GA of 28 weeks. Birth weight for GA also had a "dose-response" effect; the more growth-restricted infants had greater risk, with infants below the 3rd percentile of weight for GA having 4 times greater odds of severe ROP than those between the 25th and 75th percentiles. Male gender was also a significant risk factor (odds ratio: 1.73; 95% confidence interval: 1.25-2.40).

CONCLUSIONS

These data, for a large, essentially population-based cohort, suggest that factors related to the degree of immaturity, intrauterine growth restriction, and male gender contribute to severe ROP.

Vitamin C supplementation in very preterm infants: a randomised controlled trial

OBJECTIVE

To determine whether regulating vitamin C (ascorbic acid: AA) intake to achieve higher or lower plasma concentrations was associated with improved clinical outcome.

DESIGN

A double blind, randomised controlled trial.

SETTING

Neonatal intensive care unit at Christchurch Women's Hospital.

PATIENTS

Infants with birth weight <1500 g or gestation <32 weeks, admitted to the unit within 48 hours of birth.

INTERVENTION

Infants were randomised to one of three protocols with regard to AA supplementation for the first 28 days of life: group LL received low supplementation throughout; group LH received low until day 10 and then high: group HH received high throughout.

MAIN OUTCOME MEASURES

Primary outcome measures were oxygen requirement at 28 days and 36 weeks postmenstrual age, total days supplemental oxygen, and retinopathy of prematurity. AA concentrations were measured at study entry (day 2), and days 10, 21, and 28.

RESULTS

A total of 119 infants were enrolled over 24 months (mean gestation 28.4 weeks; birth weight 1161 g). Six infants died, and these had significantly higher AA concentrations before randomisation than surviving infants (116 micromol/l (95% confidence interval 90 to 142) v 51 micromol/l (45 to 58), p<0.0001). There were no significant differences in primary outcomes between the groups. However, the proportion of surviving infants with an oxygen requirement at 36 weeks postmenstrual age in group HH (19%) was half that in group LL (41%) (p=0.06).

CONCLUSIONS

In a randomised controlled trial, no significant benefits or harmful effects were associated with treatment allocation to higher or lower AA supplementation throughout the first 28 days of life.

Outcomes for high risk New Zealand newborn infants in 1998-1999: a population based, national study

OBJECTIVE

To determine short term morbidity and mortality outcomes, provision of care, and treatments for a national cohort of high risk infants born in 1998-1999 and admitted to New Zealand neonatal intensive care units (NICUs).

SETTING

All level III (six) and level II (13) NICUs in New Zealand.

METHODS

Prospective audit by the Australian and New Zealand Neonatal Network (ANZNN) of all infants defined as "high risk" (born at < 32 weeks gestation or < 1500 g birth weight, or received assisted ventilation for four hours or more, or had major surgery). Data were collected from birth until discharge home or death.

RESULTS

There were 3368 high risk infants (3.0% of all live births), comprising 1241 (37%) < 32 weeks gestation, 1084 (32%) < 1500 g, 3156 (94%) who received assisted ventilation, and 243 (7%) who received major surgery (categories overlap). Most infants (87%) received some care in tertiary hospitals, and 13% were cared for entirely in non-tertiary hospitals. Survival was 91% for infants < 32 weeks gestation, 97% for infants > or = 32 weeks gestation who received assisted ventilation, and 92% for infants > or = 32 weeks gestation who had major surgery. The proportion of very preterm infants who survived free of early major morbidity was 11%, 28%, 53%, 81%, and 90% for infants born at < 24, 24-25, 26-27, 28-29, and 30-31 weeks gestation respectively.

CONCLUSIONS

These unique population based national data provide contemporary information on the care and early morbidity and mortality outcomes for all high risk infants, whether cared for in hospitals with level III or level II NICUs.

Improved outcomes for very low birthweight infants: evidence from New Zealand national population based data

OBJECTIVE

To compare the survival and short term morbidity of all New Zealand very low birthweight (VLBW) infants born in two epochs, 1986 and 1998-1999.

SETTING

All level III and level II neonatal intensive care units (NICUs) in New Zealand.

METHODS

In 1986, data were prospectively collected for a study of retinopathy of prematurity (ROP). In 1998-1999, prospective data were collected by the Australian and New Zealand Neonatal Network (ANZNN). Both cohorts included all VLBW infants born during the calendar year and admitted to a NICU. Data were collected from birth until discharge home or death.

RESULTS

More VLBW infants were admitted for care in 1998-1999 (n = 1084, 0.96% of livebirths) than in 1986 (n = 413, 0.78% of livebirths; p < 0.001), including a higher proportion of VLBW infants of < 1000 g birth weight (38% v 32% respectively; p < 0.05). Survival to discharge home increased from 81.8% in 1986 to 90.3% in 1998-1999 (p < 0.001). The 1998-1999 cohort had a higher proportion of infants born in a hospital with a level III NICU (87% v 72% in 1986; p < 0.001) and receiving antenatal corticosteroids (80% v 58% in 1986; p < 0.001). In 1998-1999, the incidence of several morbidities had decreased compared with 1986, including oxygen dependency at 28 days (29% v 39% respectively; p = 0.001) and at 36 weeks postmenstrual age (16% v 23%; p = 0.002), grade 1 intraventricular haemorrhage (IVH) (8% v 24%; p < 0.001), grade 2/3 IVH (5% v 11%; p < 0.001), and stage 3/4 ROP for infants < 1000 g (6% v 13%; p < 0.001).

CONCLUSIONS

The outlook for VLBW infants in New Zealand has improved since 1986.

Long term follow up of premature infants: detection of strabismus, amblyopia, and refractive errors

AIM

To establish recommendations for long term ophthalmological follow up of prematurely born infants.

METHODS

130 infants with a gestational age (GA) <37 weeks and born between 1 November 1989 and 31 October 1990 were enrolled in a prospective study about the development of strabismus, amblyopia, and refractive errors. Infants were subdivided in three groups according to GA: A <28 weeks (n=32), B >/=28-</=32 weeks (n=64), C >32-<37 weeks (n=34). Ophthalmological assessment took place at the postconceptional age of 32 weeks, at term and at 3, 6, 12, and 30 months post term. At the age of 5 years parents received a questionnaire and a majority of the children was examined again (n=99).

RESULTS

At the age of 5 years 46 infants were known to have strabismus (n=29) and/or amblyopia (n=22) and/or refractive errors (n=22). Statistical analysis showed that gestational age, duration of supplementary oxygen, and duration of hospitalisation were important predictive variables for the development of strabismus, amblyopia, or refractive errors (SAR) at the age of 5 years (p<0.05). Infants with a GA </=32 weeks had a significantly higher risk of developing SAR than infants with a GA >32 weeks, who developed an incidence comparable with the normal population. Strabismus developed mainly in the first year of life and at the age of 5 years. Most infants with amblyopia were detected at the age of 2-3 years. Refractive errors were found in the first year of life and at the age of 2.5 and 5 years.

CONCLUSION

Infants with a GA <32 weeks should be selected for long term ophthalmological follow up. These infants should be screened at the age of 1 year, in the third year of life (preferably at 30 months), and just before school age (including testing of visual acuity with optotypes).

Protein carbonyls and lipid peroxidation products as oxidation markers in preterm infant plasma: associations with chronic lung disease and retinopathy and effects of selenium supplementation

The purpose of this study was to determine whether protein carbonyls and the lipid peroxidation product malondialdehyde (MDA) are elevated in plasma from very low birth weight (<1500 g) infants, whether they are affected by selenium supplementation, and whether they are associated with poor respiratory outcome or retinopathy. The study group comprised 173 infants enrolled in a randomized controlled trial of selenium supplementation. Plasma samples, collected before randomization, at 7 and 28 d after birth, and at 36 wk postmenstrual age, were analyzed for protein carbonyls and total MDA. Respiratory outcome was assessed as oxygen requirement at 28 d of age or 36 wk postmenstrual age and as number of days on oxygen. Protein carbonyl concentrations in very low birth weight infants were significantly higher than for adults but lower than for cord blood from term infants. Median values decreased significantly by 28 d, and there was no relationship with birth weight. MDA concentrations in very low birth weight infants overlapped the ranges for healthy adults and cord blood from term infants. They correlated positively with birth weight at 28 d but not at other times. Supplementation almost doubled plasma selenium concentrations, but carbonyls and MDA did not differ between the supplemented and unsupplemented groups. There were no significant differences in oxidant marker levels in infants who did or did not develop chronic lung disease or retinopathy. Protein carbonyls and MDA measurements in plasma do not show evidence of systemic oxidative stress in <1500-g infants and are not affected by selenium supplementation. Oxidative injury at sites such as the lung may be important in prematurity, but markers from such sites must be measured to relate to outcome and antioxidant supplementation.

Retinopathy of prematurity in infants < 32 weeks' gestation at birth in New South Wales in 1993 and 1994

OBJECTIVE

To study the incidence and severity of retinopathy of prematurity (ROP) in infants < 32 weeks' gestation.

DESIGN

Review of the records maintained in the New South Wales Neonatal Intensive Care Unit Study (NICUS) database on infants admitted to the neonatal intensive care units (NICU) in NSW from 1 January 1993 to 31 December 1994.

RESULTS

In the more premature infants, 23-26 weeks' gestation, 65% developed ROP (102 of 157 examined for ROP). Forty-four infants (28%) developed severe ROP (Stage ≥ 3 ROP), 19 infants (12.1%) required cryo/laser therapy and one infant (0.6%) in this group had a retinal detachment. One hundred and fifty-seven of 159 surviving infants (98.7%) were examined for ROP. In the infants 27-28 weeks' gestation, 38.3% developed ROP (103 of 269 examined for ROP). Fifteen infants (5.6%) developed severe ROP, seven infants (2.6%) required cryo/laser therapy for threshold ROP and three infants (1.1%) in this group had a retinal detachment. Two hundred and sixty-nine of 299 surviving infants (90%) were examined for ROP. In the infants 29-31 weeks' gestation, 10.8% developed ROP (48 of 443 examined for ROP). Six infants (1.4%) developed severe ROP, one infant (0.2%) required cryo/laser therapy for threshold ROP and no infant in this group had a retinal detachment. However, only 443 of 681 surviving infants (65.1%) in this group were examined for ROP. Of the four infants with detached retinas, one was a 25 week gestation infant weighing 840 g, two were 27 weeks' gestation weighing 960 and 980 g and one infant was a 28 week gestation infant weighing 620 g. No infant developed Stage 5 ROP.

CONCLUSION

In the more mature infants 29-31 weeks' gestation, the rate of ROP is low, although severe ROP still occurs. However, only 65.1% of these infants were examined for ROP and we should be diligent in screening for ROP in the sicker infants in this group. The incidence of severe ROP as well as the rate of cryo/laser therapy in premature infants 23-26 weeks' in NSW has not changed since the increases seen in the early 1990s. Retinal detachment also occurs in the infants 27-28 weeks' gestation and it is important that all these infants are screened for ROP.

Plasma vitamin A levels in the very low birthweight infant--relationship to respiratory outcome

OBJECTIVE

To examine the association between plasma vitamin A levels and outcome measures in very low birthweight (VLBW) infants, including meta-analysis of all observational studies.

DESIGN

A prospective observational longitudinal study of plasma vitamin A levels measured in the cord blood; maternal blood in the first 48 h after delivery; and the infants' blood at 48 h, 7 days and 28 days of age and correlated with antenatal and postnatal events. A meta-analysis of all published observational studies on the association of vitamin A with respiratory outcome in the VLBW infant was undertaken.

PATIENTS

Fifty-seven infants (88% of all eligible) VLBW infants (< 1500 g) admitted from January through October 1993 to one of two regional neonatal intensive care units in the South Island of New Zealand.

RESULTS

Exposure to antenatal steroids led to a significant increase in infant cord plasma vitamin A levels (P = 0.003), but no influence on infant plasma vitamin A levels at any other time. Exposure to postnatal steroids produced a significant rise in infant plasma vitamin A levels between 7 and 28 days (P = 0.008). After controlling for gestational age, antenatal and postnatal steroid exposure, low vitamin A levels at 48 h increased the risk of developing chronic lung disease (odds ratio for 50 microg/l decrease: 2.04, 95% CI 1.19-5.77) and bronchopulmonary dysplasia (odds ratio 1.96, 95% CI 1.14-6.87). On combining our results in meta-analysis with those of other published prospective observational studies, infants with chronic lung disease had lower plasma vitamin A levels at all times.

CONCLUSIONS

Our results support an association between low plasma vitamin A levels and adverse outcome in the VLBW infant.

Are we screening too many babies for retinopathy of prematurity?

A retrospective, hospital-records-based study of neonates screened for retinopathy of prematurity (ROP) was undertaken to determine whether the inclusion criteria for screening could have been safely altered to reduce the numbers of babies screened whilst not missing any stage III disease. Babies from six neonatal intensive care units in Birmingham were screened by a single examiner. Between November 1989 and November 1995, 1611 babies were examined and 1429 of these fell within the inclusion criteria of current guidelines for ROP screening produced by the Royal College of Ophthalmologists and the British Association of Perinatal Medicine--any baby < or = 1500 g birthweight or < or = 31 weeks gestational age. Thirty-nine (39) babies developed stage III ROP of which 31 (2.2%) were from Birmingham. In addition 8 babies with stage III ROP were referred from elsewhere. All 39 babies with stage III ROP had a birthweight < or = 1250 g or a gestational age of < or = 29 weeks, but 2 fell outside one criterion, indicating the need for both to be used. Had these inclusion criteria been utilised during this period, then 30% fewer babies would have been examined (432 of 1429). The importance of using both birthweight and gestational age as inclusion criteria is discussed, and the dangers of altering the indications for national screening on the basis of one study population is emphasised.

The correlation of elevated levels of an index of lipid peroxidation (MDA-TBA) with adverse outcome in the very low birthweight infant

The objective of this study was to examine the relationship between malondialdehyde-thiobarbituric acid (MDA-TBA) levels, as a measure of lipid peroxidation, in very low birthweight (VLBW) infants and outcome measures. A prospective observational longitudinal study was carried out in two level III neonatal units in the South Island of New Zealand measuring MDA-TBA levels in 61 VLBW infants in 1993. MDA-TBA levels were measured in (i) maternal plasma within 48 h of parturition, (ii) cord plasma, and (iii) infants' plasma at 2, 7, 14 and 28 days of age and correlated with antenatal and postnatal factors. Elevated levels of plasma MDA-TBA at 7 days were associated with adverse respiratory and ophthalmological outcome in the VLBW infants. Elevated MDA-TBA levels were measured at sample times close to the time of death in the infants who died. These results substantiate previously reported preliminary observations and support the hypothesis that oxidative injury, particularly within the first 7 days of life, is associated with the development of the long-term complications of the pre-term infant. MDA-TBA levels appear to be a useful measure to continue to explore the role of free radical mediated disease in the VLBW infant.

Towards a universal approach for screening of retinopathy of prematurity (ROP)

To improve the cost-benefit ratio of our current screening program for retinopathy of prematurity (ROP), the records of 312 infants who had been screened for ROP were studied retrospectively. Using a safety-index containing three well known risk factors (birthweight, gestational age, oxygen use), infants were classified to be at high risk or low risk for the development of ROP. When all high risk infants would have been screened extensively from the 5th postnatal week onwards and all low risk infants would have been screened once at the 7th postnatal week, a 9.8% reduction of ophthalmological examinations would have been obtained at the expense of missing 2.9% of non vision threatening ROP.

Retinopathy of prematurity in infants weighing 1000-1499 g at birth

OBJECTIVE

To review the incidence and severity of retinopathy of prematurity (ROP) in infants with birthweights 1000-1249 g and 1250-1499 g, to establish whether the upper weight limit for routine ophthalmological examination might safely be lowered.

METHODOLOGY

Prospective cohort study of infants born between 1 January 1977 and 31 December 1992 cared for in the neonatal nurseries at the Royal Women's Hospital, Melbourne. Data were retrieved on 1373 infants who survived their initial hospitalization. They comprised 657 with birthweights 1000-1249 g (group 1) and 716 with birthweights 1250-1499 g (group 2). There were 76 outborn infants in group 1 and 97 in group 2; the remaining infants were all born at the Royal Women's Hospital. Ocular examinations commenced at 2 weeks of age, when possible, and at 2-weekly intervals after that.

RESULTS

In group 1, ROP was detected in 14.6% (96/657) and severe ROP (bilateral stage 3-5) in 5.0% (33/657). Five (0.8%) children required surgical intervention (reaching threshold disease); following surgery, one was legally blind, one had severely impaired vision, and the other three had near-normal vision. Another child was blind; he was born at 28 weeks gestational age with a birthweight of 1170 g, and was transferred to a Level II hospital at 9 weeks chronological age with no detectable retinopathy. He returned 1 year later totally blind with detached retinae (grade 5 ROP). The prevalence of bilateral blindness in this group was 0.3% (2/657). In group 2, ROP was detected in 6.4% (46/716) and severe ROP in 0.8% (6/716). No children required surgery; three were found to be myopic at follow-up but the corrected visual acuity was normal. No children in group 2 were blind. No significant difference was found between the rates of ROP in inborn and outborn infants.

CONCLUSION

In neonatal units with similar rates of ROP and visual outcome, routine ophthalmological examination in the neonatal nursery of infants weighing more than 1249 g at birth is probably unnecessary.

Natural history of retinopathy of prematurity: a prospective study

The natural history of retinopathy of prematurity (ROP) has been studied prospectively in 572 infants < or = 1,700 g birthweight using a protocol designed specifically to investigate the subtle features of this condition. Acute ROP developed in 50.9%. All ROP stages 1 and 2 underwent complete resolution and of the 27 (4.7%) infants with stage 3/4 disease, cicatricial sequelae developed in six. Incidence and severity increased with decreasing birthweight and gestational age. Onset was not confined to the temporal retina but exhibited a predilection to start first in the nasal retina of the most immature neonate. The vertical retinal regions were relatively spared. Retinal arteriolar tortuosity developed around three months postnatally and was related to ROP severity but not its presence. The age at onset and rate of progression of retinopathy were largely determined by the stage of development but were also modified by systemic and local factors. The relevance of these findings to ROP screening is discussed.