Retinopathy of prematurity: clinical implications of retinal development

Association between retinal vascular measures and brain white matter lesions in schizophrenia

OBJECTIVE

Recent studies have examined retinal vascular abnormalities in schizophrenia as retinal vascular imaging is a non-invasive proxy to cerebral microvasculature. However, relation between retinal vascular abnormalities and brain structure is not well examined in schizophrenia. Hence in this study, for the first time, we examined the relationship between retinal vascular measures and brain white matter lesions in schizophrenia. We examined brain white matter lesions as they are considered a predictive marker for future adverse cerebrovascular event.

METHODS

We acquired retinal vascular images of both eyes using a non-mydriatic camera and calculated retinal vascular diameter, tortuosity, trajectory and fractal dimension using validated methods. All patients underwent Magnetic Resonance Imaging of bran and we computed white matter hypo-intensities using Freesurfer software. We performed a linear regression analysis to examine the relationship between white matter hypo-intensities and retinal vascular measures controlling for age, sex, fasting blood sugar, creatinine, whole-brain volume, and antipsychotic dose.

RESULTS

The regression model was significant in Schizophrenia patients (R=0.983;R2 =0.966;-F=10.849;p = 0.008) but not in healthy volunteers (R=0.828;R2 =0.686;F=0.182; p = 0.963). Among the retinal vascular measures, arterial tortuosity (β = 0.963;p-0.002), tortuosity (β = -1.002;p = 0.001) and fractal dimension (β = -0.688;p = 0.014) were significant predictors of white matter lesions.

DISCUSSION

The current study's findings support the conclusion that retinal vascular fractal dimension and tortuosity are associated with changes in cerebral white matter and may be considered proxy markers for cerebral microvasculature in schizophrenia. Considering the relationship between white matter lesions and stroke, these observations could have important clinical implications to screen schizophrenia patients for risk of adverse cerebrovascular event.

Nigerian neonatologists perception and experience with retinopathy of prematurity

BACKGROUND

Retinopathy of Prematurity (ROP) is an avoidable condition that affects premature infants exposed to oxygen stresses at or soon after birth. In low- and middle-income countries, like Nigeria, neonatal mortality rates are high and very few infants live to develop ROP. With recent better care, ROP is now being diagnosed.

OBJECTIVE

This study aimed to characterize what Nigerian neonatologists understand about ROP.

METHODS

At a joint meeting of Nigerian pediatric ophthalmologists and neonatologists in Kebbi State held 26-29 July 2018, questionnaires collected attendees' perspective and experience with ROP including causes, risk factors and experiences.

RESULTS

Fifty-one neonatologists out of 71 returned a completed questionnaire (response rate: 71.8%). The male:female ratio was 1:1.8, and approximately 40% were aged 41-50 years (n=20, 39.22%). Only 3 (6.39%) had experience managing infants below 500g that survived. A majority managed babies with a mean weight of 913g ± 300.37 and age of 27.87 weeks ±2.37. Most had no access to oxygen monitors (n=39,78%). Most had 10 babies to one monitor and used average settings of 90-95%. One third had seen a case of ROP (n=15,29.41%). Only 5.88% (n=3) were unaware of uncontrolled oxygen use as a risk factor. Only 4 (8.89%) had a functional screening team. None were aware of local screening guidelines.

CONCLUSIONS

Regular educational programs, collaborative clinical presentations and webinars about ROP targeted at the neonatologists and parents, including establishment of screening programs across country will likely help reduce the burden of ROP blindness in Nigeria.

Retinopathy of prematurity in port harcourt, Nigeria

Purpose. With many preterm babies now surviving as a result of improvement in neonatal care in Nigeria, the incidence of visual impairment/blindness as a result of retinopathy of prematurity (ROP) may rise. We describe our findings after screening starts for the first time in a 15-year-old special care baby unit so as to establish the incidence and risk factors for developing ROP. Methods. A prospective study carried out at the Special Care Baby Unit (SCBU) and Pediatric Outpatient Clinics of the University of Port Harcourt Teaching Hospital between January 1 and October 31, 2012. Fifty-three preterm babies (of 550 neonates admitted within the study period) delivered before 32 completed weeks and weighing less than 1500 g were included in the study following informed consent and the main outcome measure was the development of any stage of ROP. Results. Mean gestational age at birth was 28.98 ± 1.38 weeks. Mean birth weight was 1411 ± 128 g. Out of 550 babies admitted at SCBU, 87 of 100 preterms survived with 53 included in study. Twenty-five (47.2%) had different degrees of ROP with prevalence found to be 47.2%. Prevalence was higher (75%) in babies weighing <1300 g and those delivered before 30-week gestation (58%). Twenty-one (84%) had stage 1 no plus disease and 3 (12%) had stage 2 no plus disease. Only 1 (4%) had threshold disease in Zone 1. None had disease at stage 4 or 5 or AP-ROP. Receiving supplemental oxygen (χ (2) = 6.17; P = 0.01), presence of sepsis (χ (2) = 7.47; P = 0.006), multiple blood transfusions (χ (2) = 5.11; P = 0.02), and delivery by caesarian section (χ (2) = 4.22; P = 0.04) were significantly associated with development of ROP. There were no significant differences with gender, apneic spells, jaundice, or phototherapy. Conclusions and Relevance. All live infants with ROP were noted to regress spontaneously in this study. Though it may not be cost effective to acquire treatment facilities at the moment (the only child with treatable disease died), facilities for screening preterm infants displaying high risk features may be essential as smaller babies are saved.

Retinopathy of prematurity promising newer modalities of treatment

Retinopathy of prematurity (ROP) is a disorder of neonatal retinal vascularization. The incidence is increasing in developing countries like India in view of the rising numbers of preterm deliveries and improved neonatal care. Traditional modalities of treatment included cryotherapy and laser therapy, which were laborious and required special training. Hence, research is on way to find novel treatment modalities directed at various levels of pathogenesis for this blinding disease. We reviewed the published and unpublished literature on newer methods of ROP management. The pathogenesis of ROP has been studied with respect to the mediators of angiogenesis. Anti vascular endothelial growth factor (Anti-VEGF) therapy has been extensively studied and the studies have demonstrated its promising role early stages of ROP. The role of Insulin like growth factor (IGF), Granulocyte colony stimulating factor (GCSF), and June kinases (JNK) inhibitors are being studied by various researchers across the world. Gene therapy holds promise in the reversal of ROP changes.

Plus Disease: Why is it Important in Retinopathy of Prematurity?

Retinopathy of prematurity (ROP) is one of the leading causes of preventable blindness in childhood. Early posterior pole vascular signs of severe ROP have been studied since the first description of the disease. The progressive changes that take place in the posterior pole vessels of an extremely premature baby occur in a predictable fashion soon after birth. These vascular changes are described as plus disease and are defined as abnormal dilation and tortousity of the blood vessels during ROP that may go on to total retinal detachment. The ophthalmological community now has a better understanding of the pathology and cascade of events taking place in the posterior pole of an eye with active ROP. Despite many years of scientific work on plus disease, there continue to be many challenges in defining the severity and quantification of the vascular changes. It is believed that understanding of the vascular phenomenons in patients with ROP will help in designing new treatment strategies that will help in salvaging many of the eyes with severe ROP.

Fractal Analysis of the Vascular Tree in the Human Retina

The retinal circulation of the normal human retinal vasculature is statistically self-similar and fractal. Studies from several groups present strong evidence that the fractal dimension of the blood vessels in the normal human retina is approximately 1.7. This is the same fractal dimension that is found for a diffusion-limited growth process, and it may have implications for the embryological development of the retinal vascular system. The methods of determining the fractal dimension for branching trees are reviewed together with proposed models for the optimal formation (Murray Principle) of the branching vascular tree in the human retina and the branching pattern of the human bronchial tree. The limitations of fractal analysis of branching biological structures are evaluated. Understanding the design principles of branching vascular systems and the human bronchial tree may find applications in tissue and organ engineering, i.e., bioartificial organs for both liver and kidney.

Rétinopathie du prématuré : résultats de l’examen du fond d’œil chez 94 enfants à risque

PURPOSE

The purpose of this study was to evaluate the incidence and severity of retinopathy of prematurity (ROP) in infants of birth weight less than 1.500 g and/or under 32 weeks'gestation.

METHODS

Ninety-four preterm infants were examined following the Royal College of Ophthalmologists guidelines and retinopathy was graded using the International Classification of ROP. Screening limits were 1 500 g birth weight or 32 weeks'gestational age. Fundus examinations for ROP were performed at 5 weeks'chronological age from birth. Pupil dilation was obtained with instillation of 1% tropicamide three times at 15-minute intervals.

RESULTS

The 94 infants examined for ROP had a median gestational age of 292.3 weeks and a median birth weight of 1 110340 g. ROP was diagnosed in 21 of 94 subjects (22.3%) by fundus examination. ROP stage 3 developed in one preterm infant, ROP stage 2 developed in five preterm infants, and ROP stage 1 developed in 15 preterm infants. No premature babies developed stage 4 or stage 5 ROP. The disease regressed spontaneously in all cases and none of the infants required cryo/laser therapy. In the most premature infants, 23-26 weeks'gestation, 57% developed ROP and one developed severe ROP (stage 3). No disease more posterior to peripheral zone 2 was observed. The incidence of ROP was higher in infants exposed to greater than 21% oxygen (24.2%) than in infants who did not receive oxygen (17.8%). Oxygen, blood transfusion, and cardiopathy appear to be associated with an increased incidence of retinopathy of prematurity.

CONCLUSIONS

ROP continues to be a common problem associated with prematurity in France. This study found a similar incidence of prethreshold ROP when compared to recent studies. The data showed that blood transfusion and cardiopathy may play a role in the development of ROP in premature infants.

Selenium supplementation to prevent short-term morbidity in preterm neonates

BACKGROUND

Selenium is an essential trace element and component of a number of selenoproteins including glutathione peroxidase, which has a role in protecting against oxidative damage. Selenium is also known to play a role in immunocompetence. Blood selenium concentrations in newborns are lower than those of their mothers and lower still in preterm infants. In experimental animals low selenium concentrations appear to increase susceptibility to oxidative lung disease. In very preterm infants low selenium concentrations have been associated with an increased risk of chronic neonatal lung disease and retinopathy of prematurity.

OBJECTIVES

To assess the benefits and harms of selenium supplementation in preterm or very low birthweight infants.

SEARCH STRATEGY

Searches were made of the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 2, 2003), MEDLINE (1966-May 2003), and Embase (1980-May 2003). The reference lists of recent trials were also searched and abstracts from the Society for Pediatric Research from 1990 were hand-searched.

SELECTION CRITERIA

Randomised controlled trials which compared selenium supplementation either parenterally or enterally with placebo or nothing from soon after birth in preterm or very low birthweight infants and which reported clinical outcomes were considered for the review.

DATA COLLECTION AND ANALYSIS

Data on selenium supplementation dose, formulation and route of administration; mortality, oxygen requirement at 28 days and 36 weeks post-menstrual age, retinopathy of prematurity, and one or more episodes of sepsis; blood selenium and glutathione peroxidase concentrations at or close to 28 days, were excerpted by both reviewers independently. Data analysis was conducted according to the standards of the Cochrane Neonatal Review Group.

MAIN RESULTS

Three eligible trials were identified. Two trials, including one trial with a much larger sample size than the others combined, were from geographical areas with low population selenium concentrations. Meta-analysis of the pooled data showed a significant reduction in the proportion of infants having one or more episodes of sepsis associated with selenium supplementation [summary RR 0.73 (0.57, 0.93); RD -0.10 (-0.17, -0.02); NNT 10 (5.9, 50)]. Supplementation with selenium was not associated with improved survival, a reduction in neonatal chronic lung disease or retinopathy of prematurity.

REVIEWER'S CONCLUSIONS

Supplementing very preterm infants with selenium is associated with benefit in terms of a reduction in one or more episodes of sepsis. Supplementation was not associated with improved survival, a reduction in neonatal chronic lung disease or retinopathy of prematurity. Supplemental doses of selenium for infants on parenteral nutrition higher than those currently recommended may be beneficial. The data are dominated by one large trial from a country with low selenium concentrations and may not be readily translated to other populations.

Is the partial pressure of carbon dioxide in the blood related to the development of retinopathy of prematurity?

AIMS

To determine the role of carbon dioxide in the development of retinopathy of prematurity (ROP).

METHODS

This was a retrospective cohort study of 25 consecutive infants admitted to the neonatal unit with continuously recorded physiological data. The daily mean and standard deviation (SD) of transcutaneous carbon dioxide partial pressure (tcPCO(2)) was compared between infants who had stage 1 or 2 ROP and stage 3 ROP. The time spent hypocarbic (<3 kPa) and/or hypercarbic (>10 kPa and >12 kPa) was also compared between these groups. Intermittent arterial carbon dioxide tension was also measured and compared with the simultaneous tcPCO(2) data.

RESULTS

There were no significant differences in carbon dioxide variability or time spent hypocarbic and/or hypercarbic between the ROP groups on any day. 86% of transcutaneous values were within 1.5 kPa of the simultaneous arterial value.

CONCLUSION

TcPCO(2) measurement can be a very useful management technique. However, in this cohort neither variable blood carbon dioxide tension nor duration of hypercarbia or hypocarbia in the first 2 weeks of life was associated with the development or severity of ROP.

Normal neonatal values of ophthalmic and central retinal artery blood flow velocities

PURPOSE

To define standard values of blood flow velocities and indices in the ophthalmic and central retinal arteries in the neonatal period.

METHODS

Forty-two healthy full-term neonates comprised the study population. A color Doppler with mechanical sector probe was used for measuring blood flow velocity in the ophthalmic and central retinal arteries. Systolic, end diastolic, and mean-enveloped velocities were measured, and the resistance index and pulsatility index were calculated.

RESULTS

Ophthalmic artery Doppler velocities were similar on the first and third days of life, but increased significantly on the fifth and seventh days of life; resistance index significantly increased during the first week of life, whereas pulsatility index did not change significantly. Doppler velocities of the central retinal artery were similar on the first and third days; they show a delayed increase compared to the ophthalmic artery. Central retinal artery blood flow velocities increased significantly from the third to seventh postnatal day. Resistance index also increased between the first two days and on the fifth and seventh postnatal days, while pulsatility index did not change.

CONCLUSION

These data constitute a starting point for studying the possible relationship between eye circulation and pathogenesis of retinopathy of prematurity.

Vascular endothelial growth factor and hepatocyte growth factor levels are differentially elevated in patients with advanced retinopathy of prematurity

Although the roles of vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF) in angiogenesis are well described, the putative roles of these factors in retinopathy of prematurity (ROP) remain unknown. We evaluated VEGF and HGF protein levels in subretinal fluid of eyes with ROP, and expression of their corresponding receptors in retrolental membranes associated with stage 5 ROP. We examined subretinal fluid samples from eyes using rhegmatogenous retinal detachment as a control. VEGF and HGF were differentially elevated in eyes with ROP. In Stage 5 ROP (n = 22), the mean VEGF and HGF levels were 14.77 +/- 14.01 ng/ml and 16.56 +/- 9.62 ng/ml, respectively. Interestingly, in patients with active stage 4 ROP, mean VEGF levels were highly elevated (44.16 +/- 18.72 ng/ml), whereas mean HGF levels remained very low (4.77 +/- 2.50 ng/ml). Next, we investigated in vivo expression of VEGF receptor-2 and HGF receptor in retrolental membranes from 16 patients with stage 5 ROP. Both VEGF receptor-2 and HGF receptor proteins were detected mainly in posterior portions of the membrane as well as in vessel walls and along the retinal interface where angiogenesis was active. These findings together suggest that VEGF and HGF play important roles in the pathogenesis of ROP.

The effect of selenium supplementation on outcome in very low birth weight infants: a randomized controlled trial. The New Zealand Neonatal Study Group

BACKGROUND

Low selenium (SE) status has been documented in preterm infants and has been suggested to be a risk factor for chronic lung disease.

METHODS

A total of 534 infants with birth weight <1500 g were enrolled in 8 New Zealand centers in a double-blind placebo-controlled randomized trial of SE supplementation from week 1 of life until 36 weeks' postmenstrual age or discharge home. Supplemented infants received 7 microg/kg/d of SE when fed parenterally and 5 microg/kg/d when fed orally. Plasma SE and glutathione peroxidase concentrations were measured in mothers after delivery and in infants before randomization and at 28 days and 36 weeks' postmenstrual age. Primary outcome measures were oxygen dependency at 28 days and total days oxygen dependency.

RESULTS

No significant differences were seen between the groups with respect to primary or secondary outcome measures, with the exception that fewer supplemented infants had an episode of sepsis after the first week of life (P <.038). Mean plasma SE concentrations were 0.33 micromol/L before randomization in both groups and at 28 days had risen in the supplemented group (0.56 micromol/L) but fallen in the control group (0.29 micromol/L) (P <.0001). There was no association between outcome measures and SE concentrations at 28 days or 36 weeks' postmenstrual age. However, lower maternal and infant prerandomization SE concentrations were associated with increased respiratory morbidity.

CONCLUSIONS

Postnatal SE supplementation in very low birth weight infants did not improve neonatal outcome. Further investigation of SE supplementation of mothers from the second half of pregnancy is warranted.

Intra-arterial blood pressure reference ranges, death and morbidity in very low birthweight infants during the first seven days of life

OBJECTIVES

We aimed to: (1) assess the association of average, low, high and variable mean blood pressure (mbp) on death and the common morbidities of very low birthweight infants, and in doing so, (2) to derive representative reference ranges for mbp in very low birthweight infants.

STUDY DESIGN

This five year retrospective study assessed 1 min computer recordings of intra-arterial mbp in 232 very low birthweight infants over the first 7 days of life in a tertiary NICU. Four measures of mbp were assessed: average, variability, maximum (per time period), and percentage of time with a mean blood pressure less than the infant's gestation. Correlation was made with death and the development of intraventricular haemorrhage (IVH), periventricular leukomalacia (PVL) and retinopathy of prematurity (ROP).

RESULTS

The mbp increased with increasing birthweight and postnatal age (though with a slight decrease on days 6 and 7). Birthweight, gestation and colloid support (adjusted for birthweight and gestation) were the only factors significantly associated with mbp. IVH was predominantly associated with a low and variable mbp on the day IVH was noted or the day before. PVL and ROP were not associated with blood pressure.

CONCLUSIONS

These reference ranges include more infants and data than previously published and relate mbp in this cohort to morbidity and mortality. They could assist clinicians in judging appropriate mbp for birthweight.

Long-term form identification vision after early, closed, lensectomy-vitrectomy for stage 5 retinopathy of prematurity

PURPOSE

Form identification vision after early, closed, lensectomy-vitrectomy for retinopathy of prematurity (ROP) stage 5 open funnel retinal detachment is reported from a database that included 45 eyes of 27 infants. The focus of this report is the verbal responses at a mean age of 7.0 years for nine nonamblyopic (preferred) eyes of nine preterm infants with minimal developmental delay (good central nervous system function).

METHODS

All 45 eyes underwent initial cryotherapy for threshold ROP to the avascular retina to decrease the angiogenic stimulus (mean postconceptual age = 34.8 weeks) and subsequently underwent multiple cryotherapy sessions to the avascular retina and shunt with scleral buckling to decrease retinal traction (mean postconceptual age = 38.0 weeks). When tractional retinal detachment occurred with an open funnel, each eye underwent an early, closed, lensectomy-vitrectomy (mean postconceptual age = 45.7 weeks). The 34 eyes with a successful anatomic result were fitted with contact lenses as soon as possible after surgery.

RESULTS

The nine nonamblyopic eyes of nine preterm infants with minimal developmental delay had the following visual acuities using Allen figures or Snellen test types: one eye 20/80, one eye 20/200, two eyes 20/400, three eyes 20/800, and two eyes 20/ 1600.

CONCLUSION

These nine eyes support the thesis that form identification vision can be obtained by early vitrectomy for ROP stage 5 open funnel retinal detachments.

Orbital sonography in children

Orbital sonography with color-flow Doppler imaging is a relatively new technology with significant application in the pediatric patient. This review stresses the primary indications for pediatric ophthalmic ultrasound and also discusses those instances where the use of ultrasound supplements other imaging studies.

Transcutaneous oxygen levels in retinopathy of prematurity

Retinopathy of prematurity (ROP) is a potentially blinding disease of preterm infants. 21 days of computer-recorded transcutaneous oxygen (TcPO2) data were compared in 31 infants with stage 3 or greater ROP and 38 infants with no ROP or stage 1 or 2. In a multiple logistic regression adjusted for significant perinatal factors (birthweight, gestation, and intraventricular haemorrhage), babies with stage 3 or higher ROP showed an increased variability of TcPO2 in week 1 (p < 0.01) and 2 (p = 0.012) but not week 3. Variability of TcPO2 in the first 2 weeks of life is a significant predictor of severe ROP.

Severe retinopathy of prematurity in infants with birth weights less than 1250 grams: incidence and outcome of treatment with pharmacologic serum levels of vitamin E in addition to cryotherapy from 1985 to 1991

OBJECTIVE

To determine the effect of vitamin E prophylaxis and treatment on the sequelae of severe (threshold) retinopathy of prematurity (ROP) in infants treated with cryotherapy at Pennsylvania Hospital from 1985 to 1991.

STUDY DESIGN

Beginning on day 0, all infants with birth weights < or = 1250 gm received supplements of vitamin E using standard preparations. Serum E levels of 23 to 58 mumol/L (1 to 2.5 mg/dl) were targeted for infants with immature retinal vasculature or ROP of stage 2 or less in severity, and levels of 58 to 81 mumol/L (2.5 to 3.5 mg/dl) for infants with prethreshold ROP. At diagnosis of threshold ROP, treatment with a parenteral investigational new drug preparation of alpha-tocopherol was begun to raise serum levels to the pharmacologic range (93 to 116 mumol/L or 4 to 5 mg/dl). Within 3 days of diagnosis, and at the discretion of the retinal specialist, one or both eyes were treated with cryotherapy. Visual outcome at 4 years was compared with the 42-month outcome reported for eyes in the infants randomly assigned to treatment in the 1986-1987 Multicenter Trial of Cryotherapy for ROP (CRYO-ROP).

RESULTS

Threshold ROP developed in 22 of 450 surviving infants (age 3 months). All were treated with pharmacologic serum levels of vitamin E; 17 infants were also treated with cryotherapy (10 in one eye and 7 in both eyes). These 17 infants, in comparison with infants in the CRYO-ROP trial (n = 187), were at least at equal risk for poor visual outcome on the basis of birth weight, gestational age, the percentage of zone 1 ROP, and mean interval from appearance of ROP to diagnosis of prethreshold ROP, which was shorter at Pennsylvania Hospital (4.1 days for the Pennsylvania Hospital group, 10.3 days for the CRYO-ROP group). However, on the basis of the mean number of days from diagnosis of prethreshold to threshold ROP (12.5 days for Pennsylvania Hospital, 10.5 days for CRYO-ROP) and the extent of extraretinal neovascularization at threshold (mean 7.9 sectors for Pennsylvania Hospital, 9.7 for CRYO-ROP), progression of retinopathy beyond the prethreshold stage had slowed and visual outcome in the eyes of infants at Pennsylvania Hospital treated with both cryotherapy and vitamin E (worse eye used for those treated with bilateral cryotherapy) was better than that reported for the treated eye of infants in the CRYO-ROP group (percentage of favorable visual acuity, 76% vs 48%, p = 0.04; percentage of normal structure posterior retinal pole, 71% vs 38%, p < or = 0.02).

CONCLUSIONS

In this small case series, the combination of cryotherapy with anti-oxidant prophylaxis and treatment appeared to decrease the severity and sequelae of threshold ROP. This hypothesis deserves testing in a large, randomized clinical trial.

Postnatal retinal vascularization in former preterm infants with retinopathy of prematurity

PURPOSE

To study the postnatally vascularized retina in former preterm infants in whom retinopathy of prematurity (ROP) stages 2 to 4a developed and spontaneously regressed.

METHODS

Matched fundus photographs and fluorescein angiograms of the temporal peripheral retinas of 133 eyes (72 patients) were obtained after 2 years of age (mean, 7.7 years; range, 2-16.2 years) and were quantified by two masked observers with respect to the following parameters: (1) macular ectopia (in disc diameters); (2) vessel traction (in 30 degrees sectors); (3) radial length of postnatally vascularized retina (in disc diameters); and (4) capillary scaffolding of postnatally vascularized retina (as a density). These cicatricial outcomes were then compared with their active worst ROP stage.

RESULTS

Of the 133 retinal montages, the following active worst ROP stages had been documented: 30 with stage 2, 42 with stage 3 mild, 32 with stage 3 moderate, 20 with stage 3 severe, and 9 with stage 4a. As active worst ROP stage increased, macular ectopia and vessel traction increased, and radial length and capillary scaffolding of postnatal retinal vascularization decreased. Retinal holes were documented frequently in eyes with high myopia.

CONCLUSIONS

The peripheral retina in former preterm infants warrants close scrutiny for possible late rhegmatogenous retinal detachments. Prolonged retinal traction (by remnant shunt and extraretinal fibrovascular proliferation) between stable, posterior, prenatally vascularized retina, and unstable, postnatally vascularized retina may lead to the development of retinal holes characteristically located in the fragile, anterior, undifferentiated, nonvascularized retina.

Free radicals and ocular disease

Ames, Shigenaga, and Hagen recently published a thorough review of the relationship between oxidants, antioxidants, and degenerative diseases of ageing. They point out that only 9% of Americans daily consume the two fruits and three vegetables recommended by the National Cancer Institute and the National Research Council/National Academy of Science. In addition to antioxidants, these foodstuffs contain many essential micronutrients. To date, specific recommendations for antioxidant supplementation have not been made by any governmental agency or professional association. A number of clinical, basic, and epidemiological studies have implicated free radical induced lipid peroxidation in various ocular disorders. It would seem prudent that those persons at greatest risk for these disorders take some precautions, which could include sunglasses that filter ultraviolet light; hats that shield the eyes from direct sunlight; and the ingestion of fruits, vegetables, and antioxidants.

The apparent role of blood transfusions in the development of retinopathy of prematurity

During a 30-month-period, 184 very low birth weight infants from two Liverpool neonatal intensive care units were screened for evidence of retinopathy of prematurity (ROP). Seventeen clinical variables previously considered relevant to the development of ROP, blood gas and blood pressure data over the first 7 days, and the maximum stage of ROP reached in either eye were recorded, together with the need for cryotherapy and current visual status. Ninety-two infants developed any stage of ROP and 15 required cryotherapy or became blind. Logistic regression showed that only gestational age and frequency of blood transfusion were independently associated both with the risk of occurrence of ROP and its severity.

Ambient light, ophthalmic artery blood flow velocities and retinopathy of prematurity

Exposure to bright light was recently proposed as a possible risk factor for the development of retinopathy of prematurity. A semi-longitudinal Doppler ultrasound study was conducted of ophthalmic artery flow velocities at normal and increased ambient light in 22 preterm infants, at post-menstrual ages from 28 to 37 weeks. The aim of this study was to obtain relationships between ophthalmic artery blood flow velocities at various post-menstrual ages and lighting conditions and the occurrence of retinopathy of prematurity. A gradual increase in average blood flow velocities was seen between 28 and 37 weeks. A stepwise increase in flow velocity was seen in all cases when ambient light was increased from moderate to intense. Five of the 22 infants developed retinopathy. No association could be established between ophthalmic artery flow velocities or light-induced changes in flow velocity and the occurrence of retinopathy.

Inositol supplementation in premature infants with respiratory distress syndrome

BACKGROUND

Inositol influences cellular function and organ maturation. Feeding premature infants inositol-rich breast milk increases their serum inositol concentrations. Whether inositol supplementation benefits infants receiving fluids for parenteral nutrition, which are inositol-free, is not known.

METHODS

We carried out a placebo-controlled, randomized, double-blind trial to determine the effects of administering inositol (80 mg per kilogram of body weight per day) during the first five days of life to 221 infants with respiratory distress syndrome who were receiving parenteral nutrition (gestational age, 24 to 32 weeks; birth weight, less than 2000 g). All the infants were treated with mechanical ventilation and some with surfactant as well. The primary end point was survival at 28 days without bronchopulmonary dysplasia.

RESULTS

The 114 patients given inositol had significantly lower mean requirements for inspiratory oxygen (P less than 0.01) and mean airway pressure (P less than 0.05) from the 12th through the 144th hour of life than did the 107 infants given placebo. Eighty-one infants given inositol and 51 given placebo survived without bronchopulmonary dysplasia (71 vs. 55 percent; P = 0.005). In the 65 infants given surfactant, however, inositol had no effect on the degree of respiratory failure. Thirteen infants given inositol and 21 given placebo had retinopathy of prematurity (13 vs. 26 percent; P = 0.022); none of the infants given inositol had stage 4 disease, whereas 7 of those given placebo did (0 vs. 9 percent; P = 0.012). Among the infants given placebo, those who had poor outcomes (death, bronchopulmonary dysplasia, or stage 4 retinopathy of prematurity) had lower serum inositol concentrations during days 2 through 7 than those who had good outcomes (P less than 0.01).

CONCLUSIONS

The administration of inositol to premature infants with respiratory distress syndrome who are receiving parenteral nutrition during the first week of life is associated with increased survival without bronchopulmonary dysplasia and with a decreased incidence of retinopathy of prematurity.

Vitamin E therapy in retinopathy of prematurity

Vitamin E is a fat soluble antioxidant and as a result it is able to scavenge free radicals derived from oxygen. The premature infant and the retina are likely to be particularly vulnerable to the deleterious effects of these oxygen derived free radicals, and as a result prophylactic vitamin E has been suggested for the management of retinopathy of prematurity (ROP). However, despite numerous trials, prophylactic supplementation with vitamin E remains controversial. This paper will critically review the use of vitamin E in ROP and consider the risk/benefit relationship of such treatment in premature infants.

A 12-year experience of retinopathy of prematurity in infants less than or equal to 28 weeks gestation or less than or equal to 1000 g birthweight

This study reported the prevalence and severity of retinopathy of prematurity (ROP) in less than or equal to 28 weeks gestation or less than or equal to 1000 g birthweight infants over a 12-year period. Among 328 survivors of less than or equal to 28 weeks gestation, 30% had ROP, 12% had severe ROP of Stage 3 or worse, 5% had at least one blind eye and 3% were bilaterally blind. Among 201 survivors of less than or equal to 1000 g birthweight, the above abnormalities were found in 40, 16, 6 and 4% respectively. In both cohorts there was a significant increase in the prevalence of ROP and severe ROP between the period 1977-80 and 1981-84, but the lesser increase observed between the periods 1981-84 and 1985-88 was not statistically significant. The rates of ROP-induced blindness were not significantly different between the three 4-year periods. An inverse relationship was noted between the prevalence of ROP and gestational age. The results suggest a resurgence of ROP in less than or equal to 28 weeks or less than or equal to 1000 g infants, the cause of which is uncertain. In view of this trend, continued surveillance of ROP is warranted.

The pathogenesis of retinopathy of prematurity as it relates to surgical treatment

Our current surgical treatment for threshold retinopathy of prematurity (ROP) is based upon three concepts which emerged from morphologic and biochemical study of 250 pairs of whole eye donations obtained over a ten year period. 1) Spindle cells normally migrate and canalize to form inner retinal vessels, but when stressed, spindle cells secrete angiogenic factors. The clinical implication is that transretinal cryotherapy to the avascular retina is efficacious because it obliterates spindle cells. The number and timing of cryosessions are determined by the migration and kinetics of spindle cells. 2) Myofibroblasts originate from the shunt, are the major cellular component of extraretinal fibrovascular proliferation (EFP), and contract to produce retinal distortion and detachment. The clinical implication is that a second transretinal cryotherapy session should obliterate the shunt and the EFP, and should eliminate the source of retinal traction. 3) Anterior ocular growth occurs exponentially during the period when ROP develops and is treated. The clinical implication is that a prophylactic scleral buckle supports the fixed surface area of the developing retina while the choroid and sclera enlarge anteriorly. Retinal distortion produces misaligned photoreceptors, and retinal detachment results in rapid retinal death.

The rationale for cryotherapy with a prophylactic scleral buckle for Zone I threshold retinopathy of prematurity

Our current surgical protocol for Zone I threshold retinopathy of prematurity (ROP) has evolved over 15 years and is rationalized by increasing knowledge of two pathologic processes of ROP: 1) angiogenic stimulation of spindle cells (clinically invisible) near the vitreal surface of the avascular retina; and 2) tractional forces of myofibroblasts [clinically visible as extraretinal fibrovascular proliferation (EFP)] in the vitreous overlying the vascular retina. These two pathologic processes occur concomitantly with normal anterior ocular growth with a constant optic disc-macular distance. Our current surgical protocol for Zone I threshold ROP, involves complex surgeries to achieve success defined as a macula which always remains anatomically attached, but which may be distorted or ectopic. This protocol requires cryotherapy in at least two sessions. The first is to the avascular retina to destroy spindle cells. The second is to the EFP to destroy myofibroblasts and to the shunt to eliminate the site of origin of myofibroblasts. The protocol also requires the concomitant placement of a prophylactic scleral buckle to allow formation of a new complete ora serrata while remnant myofibroblasts contract and while anterior ocular growth continues.

Infants weighing 1,000 g or less at birth. Outcome at 8-11 years of age

34 long-term survivors of a five-year period (1977-1981) weighing 1,000 g or less at birth were followed-up at 8-11 years of age. Three (8.8%) children had severe functional handicap, 7 (20.6%) had moderate impairments with the need of special schooling. Twenty-four (70.6%) attended normal school but 7 (20.6%) with need of special help. The rate of survival was 30% at the single regional intensive centre where this cohort of infants were cared for. Handicapped infants differed significantly from infants with good prognosis in their neonatal requirements for oxygen therapy and in pathological conditions such as birth asphyxia and recurrent apneic spells but no differences in birthweight, gestational age, route of delivery, maternal age, social class, proportions below the tenth percentile and sex were found.