Retinopathy of prematurity. Clinical findings in a Danish County 1982-87

Visual function is reduced in young adults formerly born prematurely: a population-based study

Aims

To assess visual function in young adults born preterm and compare with full-term individuals of the same age.

Methods

Young adults, born preterm (birth weight ≤1500 g) in 1988–1990, previously included in a population-based study on the incidence of retinopathy of prematurity (ROP) in Stockholm County, Sweden were included. A control group of participants born at term, in the same area during the same time period, was used for comparison. Best-corrected visual acuities were assessed at distance and near with logMAR charts. Distance visual acuity was also measured with single symbols to calculate crowding. Visual fields were measured with Humphrey 24-2 and the mean deviation was noted. Contrast sensitivity was assessed with Vistech contrast sensitivity test and the area under the curve was calculated.

Results

Fifty-nine preterm (females 37) and 44 full-term (females 18) individuals were included. All individuals were between 25 and 29 years of age. Preterm individuals had significantly lower distance visual acuity (mean −0.08 (SD 0.11) vs −0.14 (SD 0.07) logMAR, p=0.009), near visual acuity (mean −0.08 (SD 0.11) vs −0.13 (SD 0.06) logMAR, p=0.049), mean deviation (mean −1.09 (SD 1.13) vs −0.80 (SD 1.03) dB, p=0.05) and contrast sensitivity (mean 2.02 (SD 0.19) vs 2.16 (SD 0.14), p<0.001) in the better eye compared with full-term individuals. The differences in distance visual acuity and contrast sensitivity were also evident after excluding persons with previous ROP and neurological complications. In multivariable analyses, treated ROP was a risk factor for reduced near visual acuity and visual fields.

Conclusion

Visual function seems to be reduced in prematurely born individuals even in adulthood. The reason may be prematurity per se since individuals without previous ROP or neurological complications are also affected.

Synopsis

Visual function, assessed as visual acuity, visual fields and contrast sensitivity, was reduced in young adults born preterm and previously included in a population-based study on the incidence of retinopathy of prematurity, as compared with controls.

Retinopathy of Prematurity in Denmark. Epidemiological Considerations and Screening Limits

The epidemiology of retinopathy of prematurity (ROP) in Denmark is analysed based on two sources. Regional experience is presented from 12 years' prospective ophthalmic control of infants at risk, in a Danish county with population 342,000 and 44,805 liveborns over the period 1982-93. Out of 127 subjects with ROP 101 reached stage 1 or 2 only; 26 progressed to at least stage 3. Seven with blindness due to ROP amounted to 15.6/100,000 liveborns, a high frequency. The trend over the twelve years was towards less serious sequelae. Currently, the national screening limits for ROP have been adjusted under guidance from the compulsory registration of childhood visual impairment; with birth years 1974-94 there were 157 ROP-children in the register. Blindness due to ROP is now seen only in the very immature. It is suggested that gestational age 30 weeks will soon replace the present limits of less than 32 weeks/1750 g.

Frequency and natural history of retinopathy of prematurity (ROP). A prospective study in a Swedish city 1986-1990

Frequency and natural history of retinopathy of prematurity (ROP) were prospectively studied in 142 preterm infants with birth weight (BW) less than 1501 g and/or gestational age (GA) below 33 weeks, who were born in Malmö 1986-1990. ROP developed in 27 (19%) of the 142 infants. The frequency of the ROP was significantly higher in infants with BW < or = 1000 g (54%) and in those with GA < or = 28 weeks (40%) than above these values. Infants with ROP had, compared with those without ROP, significantly lower BW, lower GA, lower Apgar score at 1 and 5 min, longer period of oxygen-therapy and higher frequency of neonatal complications. Five infants with stage 3 ROP were treated with cryotherapy; four with moderate changes showed good regression, the fifth with a severe stage 3 progressed and became blind. Up to 5 years follow-up revealed a significantly higher frequency of strabismus (40% vs 8%), myopia (25% vs 4%), and amblyopia (33% vs 6%) in infants with ROP than in those without ROP. Astigmatism and anisometropia were also frequent in children with ROP.

Visual impairment due to retinopathy of prematurity in Nordic children

The registers of visually impaired children in Denmark, Finland, Iceland and Norway have been compiled into a common database by a Nordic study group of ophthalmologists, NORDSYN. The database contains information on 2527 children aged 0-17 years. The total number of children with visual impairment due to retinopathy of prematurity (ROP) is 247. ROP is the 3rd most common single diagnosis in the database. The age-specific national prevalence of registration (N/100 000) of visual impairment due to ROP varies from 12 in Denmark to 5 in Finland and Norway and 4 in Iceland. The differences can partly be explained by varying efficiency of registration. The age-distribution indicates that visual impairment due to ROP is not decreasing. Of the 247 children 175 had a visual acuity less than 1/60 and 58 had one or more additional impairments. Incidence studies on visual impairment in Nordic children are being prepared.

Epidemiology of ROP in the Stockholm area of Sweden

A prospective, population-based study of the epidemiology of ROP in a well-defined geographical area of Sweden was performed. Two hundred and sixty children with a birth weight of 1500 g or less, and surviving for at least eight weeks, were included in the study. ROP was seen in 40.4% of the children. We suggest that prematurely born children with a gestational age of 32 weeks or less ought to be screened for ROP.

Retinopathy of prematurity in a Danish neonatal intensive care unit, 1985-1991

During the 7 year period 1985 to 1991, 170 infants born in Hvidovre Hospital, Denmark, with birthweight < or = 1500 g and gestational age < or = 32 completed weeks survived at least 8 weeks or more and had eye examinations carried out. Forty-five infants had ophthalmoscopic evidence of retinopathy of prematurity (ROP). Eighteen developed blindness or severely reduced vision and 6 developed unilateral blindness. In 21 the ROP changes regressed. Eight infants eventually developed severe myopia. The 45 infants with ROP were compared with the 125 without ROP. There was no difference in birth weight, gender, or mode of delivery. Significant difference was found in gestational age, asphyxia, intensive treatment and complications. Particularly infants with ROP born with gestational age 27 to 29 weeks needed prolonged and more intensive treatment than infants without ROP. Infants with ROP had more frequently long term sequels from the central nervous system than infants without ROP.

Retinopathy of prematurity in Frederiksborg County 1988-1990. A prospective investigation, an update

A report is given of retinopathy of prematurity findings in a Danish county (pop. 342,000) for birth years 1988-90. Out of 12,116 liveborn infants 200 were followed with eye controls during (at least) the first 3 months. In 135 gestational age and/or birth weight were below 32 weeks/1750 g. Twenty-five had ROP stage 1-2 with uneventful regression. Out of 5 with at least stage 3 ROP 2 had spontaneous regression. Three had cryotherapy; two acquired unilateral blindness, one myopia of prematurity. As part of an ongoing prospective investigation the visual results denote progress as compared to the serious results from the preceding 6 years (6 blind children). For 1982-90 the pooled ROP blindness rate amounted to 18.7/100,000 liveborn, a frequency only to be surpassed by the neighbouring Copenhagen area. Considering correct timing of cryotherapy close observation of small premature infants is recommended. At present our screening limits are 32 weeks gestational age/1750 g birth weight.

Retinopathy of prematurity in the southern part of Sweden

The incidence of retinopathy of prematurity (ROP) was studied in prematures in the southern part of Sweden during one year. Nine hospitals participated in the prospective study. During the period 23,745 children were born in the region. One hundred and ninety-three of 214 prematures of gestational age < or = 32 weeks and/or birth weight < or = 1500 g, were subjected to ophthalmic investigation. The incidence of ROP among the prematures under study was calculated to 9% (17 children). Six of them had severe ROP (3%). Some risk factors associated to ROP are discussed.

Screening for retinopathy of prematurity in a tertiary care newborn unit in Turkey: frequency, outcomes, and risk factor analysis

PURPOSE

To report the frequency, risk factors, and outcomes of screening for retinopathy of prematurity (ROP).

METHODS

Data of neonates with a gestational age of 34 weeks or less were analyzed and the predictors on the development of ROP were determined by using logistic regression analysis.

RESULTS

Of the 318 neonates, the frequency of ROP was 37.1% for any stage and 7.2% for stage 3 or greater. Treatment was needed in 16.1% of neonates with ROP. No treatment was required in neonates with a gestational age of greater than 32 weeks. Oxygen therapy, sepsis, gestational age of 32 weeks or less, and birth weight of less than 1,250 g were determined as the independent risk factors.

CONCLUSIONS

Although frequency of ROP in Turkey is similar to that in the United States, the rate of severe ROP necessitating treatment seems to be higher in Turkey. Neonates with a gestational age of 32 weeks or less, a birth weight of less than 1,250 g, sepsis, and oxygen therapy may have a greater risk of developing ROP and screening should be intensified in the presence of these risk factors.

Surveillance for retinopathy of prematurity in a Copenhagen high-risk sample 1999-2001. Has progress reached a plateau?

PURPOSE

As part of a current quality control to evaluate ophthalmic findings in two combined central Copenhagen neonatology centers for birth years 1999-2001, and to compare the selected sample with data of the national register for childhood visual impairment.

METHODS

In a prospective design to report on 372 infants mainly under regular surveillance for retinopathy of prematurity (ROP) in the stratified functional unit made up by the neonatal wards of Righospitalet (RH) and Hvidovre Hospital (HH). The median neonate under ophthalmic surveillance in the two wards (screening limits usually 32 weeks/1750 g) was given by gestational age (GA) and birthweight (BW) values of 27.3 weeks/907 g and 30.3 weeks/1420 g. respectively. Feedback regarding outcome was secured for those transferred to regional centres.

RESULTS

The overall frequency of ROP was 38.5% in the RH (n=252) and 10.8% in the HH sample (n=120). From a peak share above 60% in those <26 weeks/750 g at delivery, the incidence of ROP showed a regular decrease with decreasing immaturity. The centralized retinal ablation therapy for advanced ROP was given to a total of 29, with birth year 2001 unexpectedly showing a peak of 17 cases. Seven of the 29 children treated are now in the register for visually impaired, mainly due to low vision. Fourteen of the 29 had been very small for gestational age.

CONCLUSIONS

Supported also by recent regional Danish data, the apparent progress in the fight against ROP over many years seems to have come to a halt. Except for the continued increased survival of extremely preterm babies we have no obvious neonatological indication to explain the suggested 'adverse' trends.

Visual impairment and blindness in Europe and their prevention

The European region currently differs in many aspects, such as political, socioeconomic, and geographical. After substantial political changes at the beginning of the 1990s, the majority of central and eastern European countries started to rebuild their healthcare systems. It is apparent that eastern Europe represents a highly diverse region where the difference among countries broadens year after year. In highly industrialised countries of Europe, the leading causes of childhood serious visual loss are lesions of the central nervous system, congenital anomalies and retinal disorders. In the middle income countries of Europe, congenital cataract, glaucoma and, mainly, retinopathy of prematurity are highly expressed. The major cause of serious visual loss in adults in industrialised countries is age related macular degeneration. The other conditions comprise cataract, glaucoma, diabetic retinopathy, and uncorrected/uncorrectable refractive errors, along with low vision. In people of working age, diabetic retinopathy, retinopathy pigmentosa, and optic atrophy are the most frequently reported causes of serious visual loss. In the middle income countries of Europe, advanced cataract, glaucoma, and diabetic retinopathy are more frequently observed.

Central nervous system damage and retinopathy of prematurity--an ophthalmic follow-up of prematures born in 1982-84

Retinopathy of prematurity (ROP) was observed in 28 of 185 pre-term infants born in 1982-84 and under regular ophthalmic surveillance after delivery; their gestational age (GA) range was 25-35 weeks; four became blind. All 28 attended ophthalmic reassessment at age 7-10 years and were compared with 60 pre-term subjects of the same cohort who had not developed ROP. Considering psychomotor development, 45 (51%) of the total 88 had evidence of central nervous system (CNS) damage; minor in 24 and major in 21 (cerebral palsy in particular). With correction for drop-outs, the regional frequency of severe CNS damage was 24% for birth weight below 1500 g and 29.6% for GA less than 32 weeks. Except for the selection due to initial inclusion for ROP surveillance, we have no explanation for the high frequency at the present follow-up. Statistically, the ocular damage of ROP appeared unassociated with CNS impairment. An analysis of perinatal factors based on matched pairs did not indicate any definite association with subsequent development of ROP and/ or CNS damage.

Retinopathy of prematurity in a Danish county. Trends over the 12-year period 1982-93

An analysis of the ophthalmic recordings from the pre-term infants born 1991-93 considered at risk of developing retinopathy of prematurity is added to three previous 3-year clinical surveys from the same Danish county. Out of the 203 subjects of the recent study 34 showed evidence of retinopathy of prematurity. In 27 the maximum retinopathy of prematurity stage was 1 or 2 prior to regression. Out of the seven subjects with stage 3, one progressed to bilateral blindness in spite of the cryotherapy given in this single case. Comparing with the four retinopathy of prematurity-blind born 1982-84, the trend over the 12 years appears to be towards a better overall ophthalmic outcome. Along with an increasing number of survivors of the low GA/BW groups, the retinopathy of prematurity percentage has shown a decline, and apparently with less serious sequelae. Together with other Danish experience, eventually the present data may lead to lower screening limits for retinopathy of prematurity regarding GA/BW. Prior to this, however, there should be support from the case data currently collected in the compulsory Danish register of visually impaired children. Hence our present basic recommendation is that gestational ages up to (and including) 31 full weeks qualify for serial eye examination.

Pre-term delivery and subsequent ocular development. A 7-10 year follow-up of children screened 1982-84 for ROP. 1) Visual function, slit-lamp findings, and fundus appearance

An ophthalmic follow-up comprised 88 children aged 7-10 years who had regular screening for retinopathy of prematurity (ROP) after their pre-term delivery 1982-84. Mean values of birth weight and gestational age in the 88 were 1467 g and 31 weeks. Out of 28 with early evidence of ROP four had progressed to bilateral blindness; the remaining 24 had at least a corrected visual acuity of 0.4 at disposal. The corrected median binocular acuity for all 88 was 0.95; however, the cumulated frequency curve was significantly below a previously stated norm in full-terms. The same conclusion was valid for single eye vision. Within the material, the visual score of the 28 with early ROP was significantly lower than in the remaining 60 subjects. Ophthalmoscopy often showed tortuosity of vessels, but no specific central retinal or optic nerve lesion to explain the slight general depression of visual acuity, and opacities of media contributed in only two subjects. It is concluded, that very preterm delivery generally influences the potential for developing full visual acuity, also in individuals without evidence of early ROP. Evidence of CNS-damage negatively influenced visual acuity score.

Myopia of prematurity, clinical patterns. A follow-up of Danish children now aged 3-9 years

A discussion of myopia of prematurity is based on 16 low-birth weight children now aged 3-9 years. During their first months after delivery, retinopathy of prematurity had been observed in all but one subjects-here possibly missed due to incomplete control. Two subjects had cryotherapy. Two eyes out of 32 got blind; another 4 eyes became weak-sighted. The primary aim of the longitudinal study was to describe the variation in-and the course of-refraction, as apparent from serial examinations, the natural history so to say, to add new facets to our concept of myopia of prematurity and possibly to identify subgroups. Transient and fluctuating myopia being physiological in the first postnatal months, the diagnosis "myopia of prematurity' should not be forwarded too early. Some cases of early myopia which did not regress as usual over the first 6 months, later showed a reduction in degree of myopia over 1-2 years. Others pertained to the classical description of a stationary myopia, often of high degree, diagnosed in early childhood. Even in the favourable tail of the present distribution corrected visual acuity appeared subnormal according to age norms.

Retinopathy of prematurity: review of a seven-year period in a Danish neonatal intensive care unit

In the period 1985-1991, 21,675 infants were born at the University Hospital of Copenhagen, Hvidovre Hospital, Denmark. Two hundred and twenty-four infants (10.3%) with birth weights < or = 1500 g and gestational ages < or = 32 completed weeks were transferred to the neonatal intensive care unit of the hospital. One hundred and eighty survived to at least 8 weeks of age and 170 had eye examinations. Forty-five of the 170 infants examined (26.5%) had retinopathy of prematurity (ROP) and 18 (40%) of these developed blindness or severely impaired vision, a higher incidence than reported in other studies. Significant differences were found between infants with and without ROP for: birth weight, gestational age, Apgar score at 1 min, resuscitation, ventilator treatment, duration of supplementary oxygen, severe complications in the neonatal period and sequels from the central nervous system. Statistical analysis, corrected for correlations, showed that the occurrence of ROP was related significantly to early intubation, hypotension, persistent ductus arteriosus and necrotizing enterocolitis.

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.

Ocular findings in prematurely born children at 5 years of age

Fifty-eight prematurely born children (gestational age < or = 32 weeks) were studied at the age of 5 years. The ophthalmological examination was part of an extensive neurodevelopmental evaluation. The eye study revealed significant hyperopia (> or = + 2.0) in 22.4%, myopia (> or = -1.0 D) in 8.6%, astigmatism (> or = 1.0 D) in 12.1%, and anisometropia (> or = 1.0 D) in 12.1%. The myopic refractive error was high in all of the cases: from -6.0 to -14.0 D. Manifest strabismus was found in 24.2% and significant visual impairment or blindness in 6.9%. Optic atrophy and cicatricial retinopathy of prematurity were the main causes for severe visual defects. In the randomly selected full-term children of the same age, significant hyperopia was seen in 14.3%, astigmatism in 5.4% and strabismus in 1.8%. The pattern of the eye findings was different in the preterm children compared with those born at term.

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.

Visual impairment in Nordic children. I. Nordic registers and prevalence data

A Nordic study group of ophthalmologists, NORDSYN, has compiled data from registers in Denmark, Finland, Iceland and Norway of 2527 visually impaired children. Each record contains the following information: sex, year of birth, year of registration, classification of visual impairment, ocular diagnosis, systemic diagnosis, aetiology and evt. additional impairments. The ocular diagnoses were compiled into groups, and coding systems for aetiology and additional impairment were developed. The sex distribution revealed a dominance of males compared to the general population at the same age. Cases with non-genetic aetiology showed--through to a lesser extent--the same relative preponderance of males. The diseases in males caused by x-linked genetic factors do, therefore, not fully explain the sex distribution observed in the study. The national prevalences for registration of childhood blindness (WHO-definition: best corrected visual acuity in the best eye less than 3/60 or visual field less than 10 degrees around fixation for the ages 0-15 years) are per 100,000 child-population aged 0-15 years: Denmark 41, Finland 15, Iceland 19 and Norway 15. The differences are primarily presumed to be due to varying efficiency in registration. The proportion of visually impaired children with an additional mobility, hearing or mental impairment is between one-third and one-half of the national materials, thus indicating the need for interdisciplinary tracing of and care for the visually impaired child. This study documents the need of uniform routines for data classification of visually impaired children. The quality of the data in the present study calls for caution in the interpretation of the prevalence estimates. Incidence studies are being prepared to obtain information on whether the amount and causes of visual impairment in children with or without multiple impairments are changing.

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.

Retinopathy of prematurity. Where to set screening limits? Recommendations based on two Danish surveys

If all cases of serious ROP are to be detected, followed, and possibly treated, and the entire natural history of ROP to be recognized, screening limits should be set at no lower than gestational age 32 weeks and/or birthweight 1,750 g. These recommendations are based on the experience gained from two Danish surveys: cases registered as visually impaired (compulsory), from the whole country, covering the birth years 1971-88 (n = 142), and an epidemiological study from a Danish county comprising 411 infants considered at risk in 1982-1987; 63 infants developed ROP, eventually resulting in blindness in 6 of them.