Retrolental fibroplasia. Experience over two decades in one institution

Variable oxygen and retinal VEGF levels: correlation with incidence and severity of pathology in a rat model of oxygen-induced retinopathy

Retinal capillary quiescence is regulated by a delicate balance between proangiogenic and anti-angiogenic factors. Pathological angiogenesis is the result of a shift in this balance towards proangiogenic influences. Pathological angiogenesis is produced in a rat model of oxygen-induced retinopathy (OIR) by exposing newborn rat pups to alternating periods of hyperoxia and hypoxia. Based upon previous work, two similar exposure paradigms were investigated and compared, exposure of rat pups to alternating periods of 45 and 12.5% oxygen, and to alternating periods of 40 and 15% oxygen. The resulting retinal pathology was assessed by measurement of retinal clock hours with pathological blood vessel growth and the percentage of the retina that is avascular. The 45 and 12.5% exposure produced significantly greater incidence and severity of pathology than the 40 and 15% protocol. To explain the difference in pathology between these two very similar exposure protocols, retinal levels of proangiogenic vascular endothelial growth factor (VEGF) and VEGF receptor 2 (VEGFR2) and anti-angiogenic pigment epithelium-derived factor (PEDF) were measured by ELISA and western blot analysis at 0, 2, and 6 days post-exposure. In whole retinal lysates, there were no significant differences in VEGFR2 and PEDF levels. However, VEGF levels were approximately 48 and 78% higher on post-oxygen exposure day 0 and 2, respectively, in the group treated with alternating periods of 45 and 12.5% oxygen compared to the group treated with alternating periods of 40 and 15% oxygen. There was no significant difference in VEGF levels between these two groups on day 6 post-exposure. Therefore, the difference in pathology observed between these two experimental paradigms is associated with differences in whole retinal VEGF levels, but not changes in whole retinal VEGFR2 or PEDF levels. The results of this study suggest the existence of a threshold in the rat model of OIR, such that a small change in blood oxygen profile triggers a disproportionate increase in subsequent neovascularization, which is accompanied by more dramatic changes of retinal VEGF level than VEGFR2 or PEDF level. If a similar threshold exists for humans, it could explain why some oxygen-treated premature infants develop retinopathy and others do not, despite similar gestational ages, birth weights and clinical courses.

Trends in the incidence of severe retinopathy of prematurity in a geographically defined population over a 10-year period

OBJECTIVE

To examine trends in the incidence of severe (> or =grade 3) retinopathy of prematurity (ROP) in infants with birth weight of < or =1250 g in a geographically defined population over a 10-year period.

METHODS

An observational study was conducted of all infants who had a birth weight < or =1250 g and were born to mothers who were resident in the county of Leicestershire, United Kingdom, during the period January 1, 1990, to December 30, 1999. Cases were identified by the Trent Neonatal Survey. The incidence of severe ROP (> or =grade 3) was compared in 2 successive 5-year periods: 1990-1994 and 1995-1999.

RESULTS

Comparing the first 5-year period (1990-1994) with the second (1995-1999), the total number of live births fell (60 789 vs 56 564). However, there was a significant increase in the number of births with birth weight < or =1250 g (including live and dead; 615 vs 734; live births only: 455 vs 556). Survival to 42 weeks of infants who were born at < or =1250 g was significantly better in the latter time period (203 vs 302; odds ratio [OR] for death: 0.54; 95% confidence interval [CI]: 0.39-0.75). The number of cases of severe ROP was 4 times higher during the second time period compared with the first (9 vs 36). A significantly increased risk for the development of severe ROP was seen during the second time period (OR: 2.92; 95% CI: 1.37-6.20). Even after allowing for the change in gestation induced by the improved survival during the second time period, the increased risk remained (OR: 2.81; 95% CI: 1.27-6.21).

CONCLUSIONS

There is strong evidence that the incidence of severe ROP among infants with birth weight < or =1250 g increased in the latter half of the last decade. The increased risk seems to be independent of the increase in survival.

Arterial oxygen fluctuation and retinopathy of prematurity in very-low-birth-weight infants

OBJECTIVE

To determine the influence of arterial oxygen fluctuation on development of threshold ROP.

STUDY DESIGN

Retrospective study of 231 infants, < or =1500 g birth weight, who were admitted to Arkansas Children's Hospital NICU from January 1993 to June 1995. Fluctuation in partial pressure of dissolved arterial oxygen (PaO(2)) was expressed as coefficient of variation (CoV) for each infant. We investigated the relationship between CoV at three intervals and the risk of developing threshold ROP.

RESULTS

The odds ratio (OR) of developing threshold ROP versus prethreshold ROP or less associated with a 10% increase in the CoV during the first 5 days of oxygen therapy was 1.44, and during the first 10 days was 1.51. When analysis was restricted to infants receiving 30 days of therapy, the OR during the first 5 days of therapy was 1.67, during the first 10 days was 1.82, and during days 11-30 was 1.68.

CONCLUSIONS

Very-low-birth-weight infants experiencing fluctuating PaO(2) are at higher risk of threshold ROP.

Ophthalmological follow up of preterm infants: a population based, prospective study of visual acuity and strabismus

BACKGROUND/AIMS

Prematurely born infants are known to have an increased rate of ophthalmological morbidity. The aim of the present study was to investigate visual acuity and ocular alignment in a population of preterm infants in a geographical area, in infants with and without retinopathy of prematurity (ROP).

METHODS

A prospective population based study of ophthalmological status of preterm infants with a birth weight of 1500 g or less was performed during 3.5 years, with examinations at 6, 18, 30, and 42 months of corrected age. Visual acuity was tested using linear optotypes. Multiple regression analyses were used to analyse independent risk factors for poor vision and strabismus.

RESULTS

Poor vision (< 0.3) was detected in 2.5% (6/237) of the children. Of these, only two (0.8%) had a severe visual impairment (< 0.1). Strabismus occurred in 13.5% (31/229). Children with cryotreated ROP and neurological complications ran the highest risk of poor vision and strabismus, according to multiple regression analysis. Among children without a history of ROP or neurological complications, 34% had a visual acuity < 0.7 and 5.9% had strabismus, compared with 61% and 22%, respectively, among the children with ROP or neurological complications.

CONCLUSIONS

The overall incidence of subnormal vision and strabismus in children born prematurely was higher than in a full term population of the same age. On the basis of this study, follow up of all preterm infants screened for ROP is recommended and general guidelines are suggested.

Ocular neovascularization: an epidemiologic review

Neovascularization occurs in many eye diseases, and its epidemiologic impact is significant. However, data on the prevalence and incidence of ocular neovascularization have never been compiled to demonstrate its pervasiveness. This overview of ocular angiogenesis provides a review of the epidemiologic literature for neovascularization in various parts of the eye, including the cornea, iris, retina, and choroid. Relevant disease states are reviewed, as are their risk factors, so that their pathogenesis can be better understood. Data on the prevalence and incidence of the major diseases involving angiogenesis are synthesized to provide statistical evidence of the span and magnitude of ocular neovascularization. These prevalence and incidence data on ocular neovascularization are extrapolated to USA population data where possible, and "worst-case" estimates are calculated as well. Information was gathered with a search of the MEDLINE database, published monographs and volumes, and consultation with a number of primary authors. This study attempts to unify much of past and present epidemiologic research, and the information is presented in sections divided according to the anatomy of the eye.

The effect of postnatal growth retardation on abnormal neovascularization in the oxygen exposed neonatal rat

Severe retinopathy of prematurity (ROP) occurs in the smallest and sickest of premature infants. We hypothesized that, in a rat model of oxygen induced retinopathy, abnormal neovascularization would occur more frequently in larger litters where the pups are subject to postnatal growth retardation. Four litters of newborn Sprague-Dawley rats were studied; rats were randomly mixed to form two large litters (n = 25 each) and two small litters (n = 10 each). All litters were exposed to 7 days cyclic hyperoxia and hypoxia followed by 5 days in room air. ADPase stained retinae were evaluated in a masked manner for the presence and severity of abnormal neovascularization. Fluorescein perfused retinae were digitized and the ratios of vascularized:total retinal area were calculated using computer assisted image analysis. As expected, final weight in the large litters was less than in the small litters (15.3 +/- 3.8g vs. 23.4 +/- 2.1g, p < 0.001). Neovascularization occurred in 53% of rats in the large litters vs. 15% in the small litters (p = 0.009). Rats with retinae demonstrating neovascularization were smaller than those without (16.2 +/- 4.7g vs. 19.6 +/- 5.0g, p = 0.016). The severity of neovascularization in clock h was inversely correlated with final weight (rs = -0.35, p = 0.01) and ratio of vascularized:total retina area (rs = -0.46, p < 0.001). Smaller rat pups raised in larger litters, with resultant growth retardation, develop more frequent and more severe abnormal retinal neovascularization. Our results correlate with clinical experience in the premature infant.

Screening for retinopathy of prematurity: do former guidelines still apply?

Early detection of retinopathy of prematurity (ROP) in premature and very-low-birth-weight infants is crucial. In this retrospective study, 581 infants either with a birth weight below 1500 g or a gestational age of less than 32 weeks, or who did not fit these criteria but were judged to be at increased risk, were screened for ROP. ROP developed in 159 (27.4%). The incidence of ROP appeared to be inversely proportional to birth weight and gestational age. Infants with a birth weight below 750 g had a significantly higher risk of developing stage 3 and 4 ROP. The mean age at detection was 7.6 +/- 1.6 weeks. Nearly all of the ROP cases and all of the stage 3 and 4 cases were detected between the 5th and 10th week. Because screening should be focused on these vision-threatening stages, ophthalmic examinations should be concentrated in, but not limited to, the period between the 5th and the 10th postnatal week.

Retinopathy of prematurity

This review deals with retinopathy of prematurity (ROP), a disease characterized by retinovitreal neovascularization, eventually retinal detachment and blindness. Due to the increasing number of extremely premature newborns, it is becoming more frequent. ROP of all stages occurs in 25-35% of surviving premature newborns of gestational age up to approximately 35 weeks. Stages 3 or more occur in 5-10%, blindness in 3-5% of very immature babies. The incidence is inversely related to gestational age. Classification is internationally unified (ICROP) and describes 5 stages. Its pathogenesis has not yet been clarified. More or less proven risk factors are retinovascular immaturity, hyperoxia and possibly circulatory and respiratory instability. Prophylaxis consists in avoiding hyperoxia, and probably also in keeping the extremely premature newborn stable. Ophthalmologic examinations must be performed by ophthalmologists experienced in this field or under their direct responsibility and must be standardized. Treatment of ROP can be carried out at a certain stage by coagulation therapy.

A population based, prospective study of the development of ROP in prematurely born children in the Stockholm area of Sweden

A prospective population based study including 260 children with a birth weight of 1500 g or less was performed in the Stockholm county. The total incidence of retinopathy of prematurity (ROP) was 40.4%, while severe ROP--that is, stage 3 or more, was seen in 20.0%. Cryotherapy was performed in 10.8%. Logistic regression analysis revealed independent association of both gestational age and birth weight with ROP. The association of gestational age and ROP was significantly stronger, indicating that the degree of immaturity of the eye is a main predictive factor for the development of ROP. The purpose of a general screening for ROP is to identify children requiring cryotherapy. Based on these results it seems appropriate to include children with a gestational age of 32 weeks or less in such a programme and a first examination at 5-6 weeks of postnatal age is suggested.

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.

Regressed retinopathy of prematurity: the relationship between clinical risk factors of the newborn period and regressed retinopathy of prematurity severity in a preterm born population of Stockholm county 1976-81

In a retrospective study, clinical risk factors of the neonatal period were correlated with the severity of regressed retinopathy of prematurity (ROP) in a population of preterm infants (bw less than 1500 g and or gestational age less than 33 weeks). At the age of 5-11 years 134 out of 528 preterm born infants (25.4%) were found to be under ophthalmic care. Reliable information on eye fundus status could be obtained in 105 of them. Regressed ROP was found in 61, the moderate form in 48 (9.1%) and the severe form in 13 (2.5%) patients. Twelve patients (2.3%) had visual acuity of less than 0.3 on the worst eye and two (0.4%) of these patients were blind from ROP. Twenty-four clinical factors of the newborn period were correlated with the severity of regressed ROP. The results suggest that long oxygen exposure in combination with other factors interfering with retinal vasotonus are associated with the degree of the disease developed.

Visual acuity and visual field development after cryocoagulation in infants with retinopathy of prematurity

Visual development was studied in 10 very-low-birth-weight infants (less than 1500 g) with retinopathy of prematurity (ROP) stage 3+ who had been treated with cryocoagulation in both eyes. Binocular visual acuity (acuity cards method) and binocular visual fields (kinetic perimetry) were assessed repeatedly in the first year of life. At 12 months corrected age, visual acuity was normal in seven and impaired in three infants, who appeared to be severely myopic. Normal visual fields were found in eight infants at this age. The results indicate that cryotherapy in cases of ROP stage 3+ does not interfere with visual acuity development. The effect on visual field development needs further investigation.

Incidence and early course of retinopathy of prematurity. The Cryotherapy for Retinopathy of Prematurity Cooperative Group

In the Multicenter Trial of Cryotherapy for Retinopathy of Prematurity (ROP), 4099 infants weighing less than 1251 g at birth underwent sequential ophthalmic examinations, beginning at age 4 to 6 weeks, to monitor the incidence and course of ROP. Overall, 65.8% of the infants developed ROP to some degree; 81.6% for infants of less than 1000 g birth weight. As expected, ROP incidence and severity were higher in lower birth weight and gestational age categories. Black infants appeared less susceptible to ROP, of all severity categories, than nonblack infants. The timing of retinal vascular events correlated more closely with postconceptional age than with postnatal age, implicating the level of maturity more than postnatal environmental influences in governing the timing of these vascular events. These results include the current incidence of various severity stages of ROP found in the United States and provide new insight into the development of ROP.

A population-based study of ocular abnormalities in premature children aged 5 to 10 years

We studied the prevalence of ocular abnormalities in 528 children born prematurely (less than 1,501-g birth weight, less than 33 weeks' gestational age, or both) in Stockholm County from 1976 to 1981. The control group consisted of 1,047 randomly selected full-term children. Through various searches of the ophthalmic records from the period of 1981 to 1986 of Stockholm County, we found that 134 of the 528 premature children (25.4%) and 121 of the 1,047 full-term children (11.5%) had needed ophthalmic care for different reasons. The prevalence of ocular abnormalities was much higher in premature children than in full-term children: reduced visual acuity of 20/33 or worse in the best eye (21 of 528 [4.0%] and one of 1,047 [0.1%]); myopia (33 of 528 [6.3%] and 18 of 1,047 [1.8%]); anisometropia of 1 diopter or greater (31 of 528 [5.9%] and 15 of 1,047 [1.5%]); strabismus (52 of 528 [9.9%] and 22 of 1,047 [2.1%]); and nystagmus (13 of 528 [2.4%] and one of 1,047 [0.1%]). Children with birth weight less than 1,000 g had the highest rates of ocular abnormalities. We conclude that visual and oculomotor development of premature children should be carefully examined.

Eleven years' experience with retinopathy of prematurity: visual results and contribution of cryoablation

We report our 11 years' experience of cryotherapy for retinopathy of prematurity (ROP). Charts of 624 infants weighing under 1250 g who were admitted to our Neonatal Intensive Care Unit during 1977-87 were reviewed. Three hundred and eighty nine babies survived, and the total ROP prevalence was 57.5%. Cryotherapy was applied to 35%. Only one case (0.25%) of blindness was detected, and four babies (1%) had a final visual acuity of less than 20/200 in one eye. The complication rate following cryoablation was very low.

Compliance with a standard of care for retinopathy of prematurity in one neonatal intensive care unit

Standards of care are an integral part of providing safe and proper health care to the public. One such standard is the screening of premature infants for retinopathy of prematurity. In a retrospective chart review of 67 infants in an intensive care nursery, a high incidence of non-compliance with the standard was found in infants with over 1251-g birth weight, but that infants under 1251-g birth weight and eligible for participation in an investigation of retinopathy of prematurity had a high degree of compliance with the standard. These findings resulted in the adoption of recommendations to improve compliance with the standard.

Experimental studies on the pathogenesis of retinopathy of prematurity

The angiogenic activity of various parts of the retina in kittens with oxygen-induced retinopathy has been studied by the use of a corneal micropocket technique and chorioallantoic assay. The results indicate that in retinopathy of prematurity the most important role in the pathogenesis of fibrovascular proliferation is played by the so-called primary avascular retina, that is, that part of the retina which has not yet been vascularised during ontogenesis.

Outcome at school age of children with birthweights of 1000 grams or less

A follow-up study was done of extremely low-birthweight infants (less than or equal to 1000g) born between 1976 and 1979, a period when aggressive intervention was not routine practice. The survival rate was 19 per cent. 44 of the 46 survivors were followed to a mean age of 6 1/2 years. By five years of age 23 of the 44 children had been admitted to hospital, mainly for surgery and respiratory problems. Eight of 31 five-year-old children were growth-retarded and five of 26 were microcephalic. Among 44 children, ophthalmological problems were found in nine cases and neurosensory impairments (cerebral palsy, deafness) in seven. 12 children were mentally handicapped or had impaired intelligence (IQ or DQ less than 85). Over-all, 14 of the 44 children had impairments, severe in four cases and moderate in 10. Mean verbal IQ was significantly lower than mean performance IQ. Among 37 children in school or in remedial programs, nine required special education and another 12 in regular classes either failed or had very poor results, or needed extra professional help. Only 16 of the children had no significant problems in school. These findings indicate that extremely low birthweight (less than or equal to 1000g) represents a major risk to life, health (hospital admissions), long-term growth, neurosensory integrity, cognitive development and learning potential.

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.

Unexpected occurrence of retinopathy of prematurity: is there a need for custom-made screening procedures?

Widely differing screening routines for retinopathy of prematurity (ROP) are encountered in the literature. Because no standard pattern in the development of retinopathy of prematurity has so far been recognized and substantial differences exist between patient-populations, none of these procedures seem generally applicable. Diverse manifestations of this entity cast doubt upon the usefulness of rigid screening procedures. As illustrated by two cases, some retinas seem to be at risk of developing ROP over a considerable period of time which may even extend beyond term. It is suggested that very low birthweight neonates, suffering serious illness or undergoing anesthesia after the initial "routine" ROP screening, should be reexamined for ROP thereafter.

Continuing care for the preterm infant after dismissal from the neonatal intensive care unit

As more low-birth-weight babies survive, primary-care physicians are facing the responsibility of providing continuing care for those who have been dismissed from neonatal intensive-care units. Premature infants often require outpatient care for bronchopulmonary dysplasia, apnea, retinopathy of prematurity, intraventricular hemorrhage, hearing loss, hypothyroxinemia, anemia, neurodevelopmental sequelae, assessment of growth and nutrition, immunizations, and psychosocial stress. In this review, we present guidelines for the primary-care physician for the management of these conditions in preterm infants.

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

To determine whether the use of continuous transcutaneous oxygen monitoring (tcPO2) could reduce the incidence of retinopathy of prematurity (ROP) in pre-term infants receiving oxygen therapy, a randomized, prospective trial of constant monitoring using the transcutaneous oxygen monitor versus intermittent monitoring of oxygen was performed on a population of premature infants at very high risk for the development of ROP. Two hundred ninety-six infants were randomly assigned to either a constantly monitored (CM) or standard care (SC) group. CM infants had tcPO2 monitored continuously as long as they required supplemental oxygen, whereas SC infants had tcPO2 monitored only during the more acute state of their illness. Management of both groups was otherwise identical. One hundred one of 148 infants in the CM group and 113 of 148 in the SC group survived. The overall incidence of ROP was 51% in the CM group and 59% in the SC group (no significant difference). In infants over 1000 g birthweight, as the weight increased there was increasing risk of developing ROP in the SC group. The odds ratio for the ROPsc:ROPcm reached 7.6 in infants between 1200 and 1300 g in infants with Apgar scores greater than or equal to 8 at 5 minutes. The incidence of cicatricial ROP was similar in both groups: four in the CM and five in the SC group.

Retinopathy of prematurity

This paper briefly reviews Retinopathy of Prematurity. It outlines the present incidence and risk factors, summarises the ophthalmic pathology and suggests a scheme of ophthalmic examination and management.

Transcutaneous oxygen monitoring and retinopathy of prematurity

This study was performed to determine whether the use of continuous tcPO2 monitoring could reduce the incidence of ROP in preterm infants receiving oxygen therapy. Two hundred and ninety-six infants with birth weights less than or equal to 1300 grams were randomly assigned to a continuous monitoring (CM) or a standard care (SC) group. CM infants had tcPO2 monitored continuously as long as they required supplemental oxygen while SC infants had tcPO2 monitored only during the more acute state of their illness. Management of both groups was otherwise identical. One hundred and one of 148 infants in the CM and 113 of 148 patients in the SC groups survived. Mean birth weights and gestational age were similar in both groups. Duration of mechanical ventilation and oxygen therapy was also similar. The overall incidence of ROP was 51% in the CM and 59% in the SC group. As birth weight for infants greater than or equal to 1000 grams increased a higher risk for developing ROP was noted in the SC group. Four infants in the CM and 5 in the SC group developed cicatricial ROP. These results suggest that continuous tcPO2 monitoring may reduce the incidence of ROP in infants with birth weights greater than 1000 grams, but not in the smaller infants in whom this complication occurs more frequently and is more severe.

Long-term results of cryotherapy for active stages of retinopathy of prematurity

Between 1976 and 1980, retinopathy of prematurity (ROP) stage III (moderate) (fibrovascular proliferation) developed in 29 eyes (confluent fibrovascular proliferation of 3 clock hours in extension) of 17 preterm babies. The eyes were treated by cryopexy to the avascular retina. Analysis of the visual function and anatomic results in these eyes, five to eight years postoperatively, revealed very good visual function and only a few anatomic abnormalities. Comparison of these eyes with those of two groups of age- and birth-weight-matched preterms (one with less severe ROP, not treated by cryopexy, and the other with no ROP) showed that the degree of myopia was significantly higher in the cryotreated group. Although not statistically significant, there was a higher incidence and a greater degree of astigmatism in this study group.

Ocular sequelae of preterm birth and their relation to ultrasound evidence of cerebral damage

The eyes of 177 very preterm (less than 33 weeks' gestation) infants, born between 1979 and 1982 and admitted to a neonatal intensive care unit, were examined as part of an ongoing follow-up study of neurodevelopmental outcome. Ocular pathology was diagnosed in 37 (21%) of the 177 infants: 14 (8%) had retinopathy of prematurity (ROP)--progressive in three--and nine (5%) infants had delayed visual maturation (DVM). The ocular pathology was permanent in 26 (15%) of the 177 infants. Refractive errors were the commonest problem and accounted for permanent sequelae in eight of the 14 infants with ROP and two of the nine with DVM. The presence or absence of ROP was related to a wide range of prospectively coded perinatal variables and to the results of routine neonatal ultrasound brain scans and neurodevelopmental follow-up assessments made in the first 18 months of life. As in previous studies, infants with ROP were of shorter gestation, lower birth weight, and required oxygen therapy for longer than unaffected infants, but the condition was only weakly associated with other indices of respiratory illness. In contrast, ROP was strongly associated with evidence of brain damage, often consistent with hypoxic ischaemic injury. We conclude that an underlying lesion in ROP may be hypoxic ischaemic damage to the retinal circulation.

An international classification of retinopathy of prematurity. Clinical experience

A central problem in medicine is the development of classification systems of disease adequate to describe the many manifestations by which a disease may present to the clinician. Such is the problem presented by retinopathy of prematurity (ROP). A group of 23 ophthalmologists, representing 11 countries, met over a period of two years to develop a new classification. This paper presents the classification (previously published) and the author's experience with its use in classifying the disease in 121 infants of birthweight less than or equal to 1300 grams over a 15-month period.

Retinopathy of prematurity: review of a four-year period

For a four-year period the development of retinopathy of prematurity (ROP) was determined among neonates considered at risk of acquiring this condition. Fifty-six out of 249 premature infants developed some degree of ROP. Comparison of these infants with a group of 56 controls, admitted to hospital in the same period and matched for sex, birth weight, and gestational age, showed significant differences for sepsis, blood transfusions, and the period of oxygen monitoring in relation to the period of oxygen administration. The most consistent factor associated with the development of ROP was gestational age at the time of birth, though no gestational age group was entirely devoid of ROP. This suggests that screening for ROP should not be restricted to high-risk premature infants only.

The treatment of advanced retinopathy of prematurity by cryotherapy and scleral buckling surgery

Seventeen eyes of nine extremely premature infants with severe acute proliferative retinopathy of prematurity (ROP, Grades III-V) were treated. Cryotherapy alone was used in ten eyes to ablate extensive areas of avascular retina to thereby induce involution of widespread intravitreous neovascularization. No attempt was made to directly treat the arteriovenous shunt or neovascularization itself. Scleral buckling surgery was used in combination with cryotherapy in seven additional eyes to relieve diffuse vitreous traction to intravitreous neovascularization which had caused extensive traction retinal detachment. Cryotherapy was uniformly successful in causing involution of widespread intravitreous neovascularization in all patients treated. Scleral buckling surgery was initially effective in reattaching the retina in all cases but late manifestations of severe ongoing vitreoretinal traction required additional open-sky vitrectomy in two eyes and resulted in inoperable recurrent total traction retinal detachment in one eye and extensive macular scarring in another. A comparison is made between the proliferative retinopathies seen in ROP and diabetes mellitus and a rationale for effective cryotherapy in ROP is presented. In our clinical experience, the single most important prognostic factor determining the potential severity of ROP is the width and extent of the retinal avascular zone. The wider the zone, the greater the probability of rapid progression from early to advanced grades of disease.

The natural history of active retinopathy of prematurity

Two hundred twenty-one premature infants were examined in the premature nursery. Thirty-seven of the 221 (16.2%) had retinopathy of prematurity (ROP). Eight patients (21.5%) went blind and three other infants lost sight in one eye for a total of 19 sightless eyes (25.7%). The remaining 55 eyes (74.3%) retained vision. Birth weight was the most critical prognostic factor. Of eight babies who became blind all were under 1000 grams at birth, while babies who showed little change from active ROP were generally over 1300 grams. Nine of 14 eyes with only peripheral shunts (64%) resolved without dragging of the retina in the posterior pole. Sixteen eyes developed peripheral retinal detachment, and six of the sixteen (37.4%) had associated dilation and tortuosity of vessels in the posterior pole. Only one of these eyes resolved with minimal sequelae, suggesting that peripheral retinal detachment with dilated tortuous vessels was the most significant indicator of serious consequences.

Retinal disorders of childhood

Included in this discussion of retinal disorders affecting infants and children are retrolental fibroplasia, diabetic retinopathy, sickle cell retinopathy, retinal detachment, retinal hemorrhages of neonates, macular disease, colobomas, ocular toxocariasis, and TORCH syndrome.