Visual impairment in Nordic children. II. Aetiological factors

Etiology of Childhood Blindness in Izmir, Turkey

PURPOSE

To identify the anatomic sites and the etiology of childhood blindness and to discern treatable and preventable causes.

METHODS

The records of 998 patients seen in the authors' pediatric ophthalmology unit between June 1998 and May 2002 were examined retrospectively. A total of 148 patients who had visual impairment and blindness according to World Health Organization criteria were included in the study. They are classified according to the etiology based on time of insult and the anatomic site of visual loss.

RESULTS

The most common anatomic site of visual loss was retina, with a rate of 25.0%. The etiology according to the time of insult was unknown in 45.2% of the patients, of whom 20.2% had cataract. Genetic disorders were responsible in 25.0% of the patients. In 69.6% of the patients, the causes of visual impairment were considered either preventable or treatable, including cataract, retinopathy of prematurity, genetic disorders, and refractive errors.

CONCLUSIONS

A high percentage of our patients had avoidable causes of childhood blindness. Genetic counseling services, as well as national screening programs for amblyopia, red fundus reflex, and retinopathy of prematurity, should be established.

Retinal dystrophy and congenital glaucoma as major causes of vision loss in students attending two institutions for the visually disabled in Tunis city, Tunisia

PURPOSE

To assess vision loss, identify affected anatomical sites, determine etiologies and potentially avoidable causes in students attending two institutions for the visually disabled in Tunis city.

METHODS

A visit for a complete ophthalmological examination was performed. All students attending these schools were recruited in our study. The World Health Organisation Programme for the Prevention of Blindness (WHO/PBL) examination record for children was used. Data was analysed by the SPSS version 17 statistical software.

RESULTS

A total of 172 students were recruited with mean age of 11.9±3.3 years (between 6 and 18 years). One hundred and thirty-seven (79.6%) were under 16 years. The sex-ratio was 1.17. Ninety students (52.3%) had low vision and eighty-two (47.7%) were blind. We reported retina (29%), whole globe (29%), globe appears normal (11%) and optic nerve (9.8%) as the common sites of ocular abnormalities. Retinal dystrophy (22.7%) and congenital glaucoma (22.7%) were the most reported ocular diseases. The main etiologies were hereditary (54.1%) and unknown (30.8%). Consanguinity was reported in 108 students (62.8%), and fifty-five students (32%) had a positive family history. Overall, 50.5% (87/172) of ocular diseases were potentially treatable or preventable.

CONCLUSION

Retinal dystrophy and congenital glaucoma were the most common eye diseases. Heredity was the main etiology, and consanguinity was high. To decrease their incidence, awareness of the family members of the risks of consanguinous marriage and appropriate therapy for congenital glaucoma/cataract may significantly improve the child's visual prognosis.

Screening for ocular dysfunction in children: approaching a common program

According to the general principles of screening, detection of visual impairment in children is worthwhile, since the condition is a serious health problem, reliable diagnostic tests are available and effective treatment is possible in most instances of ocular and visual dysfunction. However, an evaluation of the screening procedures has not been properly done and the cost-benefit of screening has not been studied. The aim of the present study is to perform a systematic analysis of the screening programs for detection of visual dysfunction. In the screening two parts can be separated, one that concerns the more serious ocular and visual conditions which have to be discovered by general survey methods very early in life, and one that involves detection of less serious conditions, mainly amblyopia, which can be diagnosed by testing for monocular reduction of visual acuity at about 3-4 years of age. The performance characteristics of the screening programs used in Sweden and Canada were evaluated and found to be very favourable. Based on the analysis and the evaluation, recommendations are made on programs for vision screening in children that could be applied more widely. The program could involve all or parts of the following: 1) A careful inspection of the eyes in the neonatal period and preferably also examination of the red reflex with the ophthalmoscope. 2) Children at high risk for ocular and visual disorder, i.e. those born prematurely before 32 weeks of age, or with genetic disease, hearing deficit and/or neurological and mental disorder, should be examined at the proper age by an ophthalmologist. 3) All staff at pediatric departments and child health care centers should be familiar with the visual development of the normal baby and should be alerted to the various symptoms and signs which first warn parents that there may be a visual defect. An inspection of the eyes to detect squint should be part of all pediatric examinations. 4) A screening test of monocular visual acuity in 4 year-old children can be reliably performed by non-ophthalmic personnel after proper training. The screening test should be repeated by school nurses during the first grade of school, and at regular intervals during the school years. 5) The children that screen positively should be seen by ophthalmologists, and in some cases by orthoptists, without undue delay for diagnosis and treatment.

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.

A novel method of notification to profile childhood visual impairment in Scotland to meet the needs of children with visual impairment

The purpose of this study is to pilot a new notification system for children with visual impairment (VI) and describe the initial summary findings. A system of notification of children in Scotland with VI was established. Information concerning this system was distributed to professionals working with visually impaired children to forward to parents. Parents, teachers and health professionals were all encouraged to notify children with VI. 975 families with children with (VI) were notified and received information and support from Visual Impairment Scotland (VIS). For this review, the data from 850 parents were included in the analysis. The provision of a range of support services for parents and children with VI has led to a wide range of children being notified to VIS. The causes of VI can be recorded as well as other useful demographic information. The methods used could be applied across the range of low incidence childhood disabilities.

Recent trends in visual impairment and blindness in the UK

OBJECTIVE

To study recent trends in the cumulative incidence of visual impairment in childhood over a 15-year period and to assess progress against WHO goals for prevention.

DESIGN, SETTING AND PARTICIPANTS

Data from a population-based register of visual impairment in southern England were used to estimate cumulative incidence and trends in visual impairment (VI) and severe visual impairment/blindness (SVI/BL) for children born in 1984-1998. Causes were classified by anatomical site(s), timing of insult(s) and whether the visual impairment was potentially preventable or treatable.

RESULTS

Of 691 eligible children, 358 (53%) had VI and 323 (47%) SVI/BL. The cumulative incidence of VI to age 12 years was 7.1 (95% CI 6.4 to 7.8) per 10,000 live births and for SVI/BL was 6.2 (95% CI 5.6 to 6.9); the incidence of both decreased significantly over time. There was an inverse relationship with gestational age and birth weight, although the risk of visual impairment associated with prematurity and low birth weight decreased substantially over time. 55% of children with VI and 77% with SVI/BL had other impairments; the proportion of associated impairments among children with VI decreased over time. 130 (19%) of the children have died, with over half dying before the age of 5.

CONCLUSIONS

There is evidence of a temporal decline in the incidence of VI and SVI/BL in births from 1984 to 1998 especially in very preterm and low birthweight infants. Early childhood mortality was high. The causes of visual impairment in UK children are numerous, complex and often part of a wider picture of childhood disability.

Visual dysfunctions and ocular disorders in children with developmental delay. I. prevalence, diagnoses and aetiology of visual impairment

PURPOSE

To describe the prevalence, diagnoses and aetiologies of visual impairment in children with developmental delay (DD) in a Danish county with a population of 618 000 citizens.

METHODS

We carried out a cross-sectional study in Copenhagen County of children aged 4-15 years with profound to borderline DD (IQ <or= 80). Children were located through school psychologists or paediatric clinics. The number of children with DD was estimated using the capture-recapture method.

RESULTS

A total of 1126 children fulfilled the inclusion criteria, corresponding to 97.7% of the estimated number of children with DD in the county. Ophthalmological examinations were performed in 923 children. The prevalence of visual impairment was 10.5% in the study group and 22.4% in those with an IQ <or= 50. The diagnoses were predominantly cerebral visual impairment, optic atrophy, retinal dystrophies and congenital nystagmus. The aetiology of visual impairment was prenatal in 54 children, perinatal in 29 children and postnatal in seven children.

CONCLUSIONS

Visual impairment is highly increased in children with DD and is correlated to low IQ.

Retrospective Analysis of Refractive Errors in Children With Vision Impairment

PURPOSE

Emmetropization is the reduction in neonatal refractive errors that occurs after birth. Ocular disease may affect this process. We aimed to determine the relative frequency of ocular conditions causing vision impairment in the pediatric population and characterize the refractive anomalies present. We also compared the causes of vision impairment in children today to those between 1974 and 1981.

METHODS

Causes of vision impairment and refractive data of 872 children attending a pediatric low-vision clinic from 1985 to 2002 were retrospectively collated. As a result of associated impairments, refractive data were not available for 59 children. An analysis was made of the causes of vision impairment, the distribution of refractive errors in children with vision impairment, and the average type of refractive error for the most commonly seen conditions.

RESULTS

We found that cortical or cerebral vision impairment (CVI) was the most common condition causing vision impairment, accounting for 27.6% of cases. This was followed by albinism (10.6%), retinopathy of prematurity (ROP; 7.0%), optic atrophy (6.2%), and optic nerve hypoplasia (5.3%). Vision impairment was associated with ametropia; fewer than 25% of the children had refractive errors < or = +/-1 D. The refractive error frequency plots (for 0 to 2-, 6 to 8-, and 12 to 14-year age bands) had a Gaussian distribution indicating that the emmetropization process was abnormal. The mean spherical equivalent refractive error of the children (n = 813) was +0.78 +/- 6.00 D with 0.94 +/- 1.24 D of astigmatism and 0.92 +/- 2.15 D of anisometropia. Most conditions causing vision impairment such as albinism were associated with low amounts of hyperopia. Moderate myopia was observed in children with ROP.

CONCLUSIONS

The relative frequency of ocular conditions causing vision impairment in children has changed since the 1970s. Children with vision impairment often have an associated ametropia suggesting that the emmetropization system is also impaired.

Characteristics of infants with severe retinopathy of prematurity in countries with low, moderate, and high levels of development: implications for screening programs

OBJECTIVE

Retinopathy of prematurity (ROP) is a potentially avoidable cause of blindness in children. The proportion of blindness as a result of ROP varies greatly among countries depending on their level of development, being influenced by the availability of neonatal care, neonatal outcomes, and whether effective screening and treatment programs are in place. The objective of this study was to compare characteristics of premature infants who developed severe ROP between 1996 and 2002 in highly developed countries with less developed countries.

METHODS

This was an observational study. A questionnaire was completed by ophthalmologists in countries with low, moderate, and high development rankings (3 highly developed countries and from 10 less well-developed countries) who screen for ROP in which they supplied birth weights and gestational ages (GAs) of infants who were treated for threshold ROP or identified with more advanced stages of the disease. Birth weights and GAs of infants with severe ROP were measured.

RESULTS

The mean birth weights of infants from highly developed countries ranged from 737 to 763 g compared with values ranging from 903 to 1527 g in less developed countries. Mean GAs of infants from highly developed countries ranged from 25.3 to 25.6 weeks compared with 26.3 to 33.5 weeks in less developed countries. A total of 13.0% of 1091 infants from poorly developed countries exceeded United Kingdom screening criteria; 3.6% exceeded a criteria of <34 weeks' GA and/or <1750 g birth weight.

CONCLUSIONS

These findings suggest that larger, more mature infants are developing severe ROP in countries with low/moderate levels of development compared with highly developed countries. ROP screening programs need to use criteria that are appropriate for their local population.

Visual impairment in children born at full term from 1972 through 1989 in Finland

OBJECTIVE

To investigate the incidence, prevalence, and causes of visual impairment in children born at full term and to determine conditions and factors associated with visual impairment.

DESIGN

Retrospective, cross-sectional, population-based study.

PARTICIPANTS

All visually impaired individuals from 0 to 17 years of age who were born at full term from 1972 through 1989 in Finland and recorded in the Finnish Register of Visual Impairment (n = 556) were eligible for this study.

METHODS

Data in the Finnish Register of Visual Impairment relating to 556 subjects were supplemented with data from hospital records and other national registers (Register of Births, Register of Congenital Malformations, Finnish Care Register, and Finnish Cancer Register). Data relating to the children born at full term were compared with Finnish perinatal and vital statistics and with data concerning children born prematurely. The chi-square test (Mantel-Haenszel) and stepwise logistic regression analysis were used in statistical analysis of the data.

MAIN OUTCOME MEASURES

Visual acuity, time of onset of visual impairment, ophthalmic diagnosis of visual impairment, systemic disease, multiple handicap, 5-minute Apgar score, prenatal disorders, perinatal disorders, disorders arising during infancy and childhood, and treatment.

RESULTS

Four hundred thirty-one of the 556 individuals with visual impairment (78%) had been born at full term. Visual impairment was predominantly associated with genetic (53%) and prenatal (34%) factors. Ocular malformations (34%), retinal diseases (31%), and neuro-ophthalmologic disorders (26%) were the main ophthalmic diagnoses. Optic nerve atrophy (20%) and congenital cataract (13%) were the most common single diagnoses. The occurrence of blindness, systemic disease, and multiple handicap was 40%, 43%, and 45%, respectively.

CONCLUSIONS

The incidence of visual impairment in children born at full term did not decline during the 2 decades covered by this study. The findings reflected the lack of treatment for genetic eye diseases. The results also confirmed an obvious need for further understanding of mechanisms underlying congenital anomalies of the human visual system.

Risk factors in term children for visual impairment without a known prenatal or postnatal cause

Risk factors were studied for visual impairment in children without known pre- or postnatal cause, for a decrease of visual acuity. Children born at term 1979-98 and with a visual impairment were identified from the Swedish Register of Visually Impaired Children and data were linked with the Swedish Medical Birth Registry. Maternal characteristics such as maternal age, parity, maternal smoking habits in early pregnancy, maternal education, nationality, and subfertility were studied as well as maternal diagnoses such as pre-eclampsia, prolonged second stage of labour, abruptio placentae, and placenta praevia. Mode of delivery was analysed as well as birthweight, and birthweight in relation to gestational age. Abruptio placentae turned out to be the strongest risk factor (OR = 8.24 [95% CI 5.01, 13.51]). Smoking did not give a statistically significant increased risk. There is an increased risk with breech delivery (OR = 2.01 [95% CI 1.28, 3.17]). Pre-eclampsia was associated with an increased risk (OR = 2.22 [95% CI 1.46, 3.38]). There is also an increase in risk at low birthweight and small-for-gestational-age as well as birthweight > 4 kg and large-for-gestational-age. In this study we found that risk factors particularly worth noticing in term children with a presumed perinatal cause of visual impairment are abruptio placentae, pre-eclampsia, excessively low as well as excessively high birthweight, and breech delivery, a fact worth noticing in current discussion on risks, advantages or excessive exploitation of caesarean section.

Visual impairment in children born prematurely from 1972 through 1989

PURPOSE

To investigate the incidence and causes of visual impairment in children born prematurely in Finland from 1972 through 1989, and to determine what conditions and factors were associated with its occurrence.

DESIGN

Retrospective, cross-sectional study.

SUBJECTS

All visually impaired individuals from 0 to 17 years of age who had been born at fewer than 37 gestational weeks in Finland from 1972 through 1989 for whom records were available in the Finnish Register of Visual Impairment were eligible for this study.

METHODS

Data in the Finnish Register of Visual Impairment relating to 556 children were supplemented with data from hospital records, and from the Register of Births, the Register of Congenital Malformations, the Finnish Care Register, and the Finnish Cancer Register. Data relating to causes associated with visual impairment in particular were collected. Data relating to the children born prematurely were compared with data relating to children born at full term. The chi-square test (Mantel-Haenszel), the Mann-Whitney U test, Fisher exact test, and stepwise logistic regression analysis were used in statistical analysis of the data.

MAIN OUTCOME MEASURES

Visual acuity, ophthalmologic diagnoses, associated systemic disease, multiple handicap, gestational age, birth weight, 5-minute Apgar scores, and prenatal, perinatal, and infantile or juvenile disorders or disease and treatment.

RESULTS

One hundred twenty-five of the 556 visually impaired children (23%; 11/100000 children less than 18 years of age) had been born preterm. Retinopathy of prematurity, optic atrophy, and cerebral amblyopia were the main diagnoses associated with visual impairment (in 46%, 28%, and 12% of cases, respectively). Sixty-six percent of those born prematurely with visual impairment were also affected by other handicaps (mental, motor, auditory), 54% by cerebral palsy and 36% by epilepsy. Eighty-eight of the 125 children (70%) born preterm with visual impairment were blind. Very low birth weight (<1500 g), young gestational age (fewer than 30 weeks), prenatal infection, hyperbilirubinemia, respiratory disorders, asphyxia, and lengthy mechanical ventilation were associated with an increased risk of visual impairment.

CONCLUSIONS

Premature birth was a major risk factor of severe visual impairment and blindness in childhood. The visual impairment often was accompanied by cerebral palsy, epilepsy, and other motor and mental handicaps. Retinopathy of prematurity, optic atrophy, and cerebral amblyopia were the main diagnoses associated with visual impairment. During the 18 years covered by the study, the increasing incidence of survival of infants born weighing fewer than 1500 g was associated with increasing incidence of blindness.

A survey of visual impairment in children attending the Royal Blind School, Edinburgh using the WHO childhood visual impairment database

PURPOSE

To assess the aetiology and changing patterns of childhood blindness in one school for the blind in the UK and to assess the use of the World Health Organisation Prevention of Blindness (WHO/PBL) methodology and reporting form in a developed country.

METHODS

One hundred and seven children in one school for the blind and visually impaired in Edinburgh were examined using the WHO/PBL childhood blindness assessment form.

RESULTS

Of the 107 children examined, 87 (81%) were blind or severely visually impaired (corrected visual acuity of <6/60 (20/200) in the better eye). Perinatal related blindness (40%), hereditary disease (26%) and developmental factors (26%) formed the three largest aetiological categories.

CONCLUSION

The pattern of childhood blindness seen in this study was similar to reports from other developed countries. The WHO/PBL reporting form allows detailed comparisons between countries and over time. Additional fields for more detailed reporting of cerebral visual impairment and associated handicaps would increase the usefulness of the WHO/PBL form for population-based studies and for use in developed countries.

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.

Optic nerve hypoplasia: Risk factors and epidemiology

OBJECTIVES

To study the epidemiology of optic nerve hypoplasia.

DESIGN AND METHODS

Children with optic nerve hypoplasia and visual impairment were identified through the Swedish Register of Visually Impaired Children. Pre- and perinatal characteristics were obtained from the Medical Birth Registry and by scrutinizing pregnancy and delivery records. Clinical characteristics of children with optic nerve hypoplasia are described. The following risk factors were studied: maternal age, parity, maternal smoking, gestational duration, birth weight, delivery method, Apgar score, maternal disease during pregnancy, drugs used in early pregnancy.

RESULTS

Young maternal age, first parity, maternal smoking, preterm birth and factors associated with preterm birth were risk factors for optic nerve hypoplasia. There was an indicated association with the use of fertility drugs and antidepressant drugs.

CONCLUSIONS

Optic nerve hypoplasia is apparently associated not only with other anomolies, notably of the central nervous system, but also with signs of general disturbance in fetal development.

Causes of severe visual impairment and blindness in children attending schools for the visually handicapped in the Czech Republic

AIMS

To describe the causes of severe visual impairment and blindness in children in schools for the visually handicapped in the Czech Republic in 1998.

METHODS

Pupils attending all 10 primary schools for the visually handicapped were examined. A modified WHO/PBL eye examination record for children with blindness and low vision was used.

RESULTS

229 children (146 males and 83 females) aged 6-15 years were included in the study: 47 children had severe visual impairment (20.5%) (visual acuity in their better eye less than 6/60), and 159 were blind (69.5%) (visual acuity in their better eye less than 3/60). Anatomically, the most affected parts of the eye were the retina (124, 54.2%), optic nerve (35, 15.3%), whole globe (25, 10.9%), lens (20, 8.7%), and uvea (12, 5.2%). Aetiologically (timing of insult leading to visual loss), the major cause of visual impairment was retinopathy of prematurity (ROP) (96, 41.9 %), followed by abnormalities of unknown timing of insult (97, 42.4%), and hereditary disease (21, 9.2%). In 90 children (40%), additional disabilities were present: mental disability (36, 16%), physical handicap (16, 7%), and/or a combination of both (19, 8%). It was estimated that 127 children (56%) suffer from visual impairment caused by potentially preventable and/or treatable conditions (for example, ROP, cataract, glaucoma).

CONCLUSIONS

Establishing a study group for comprehensive evaluation of causes of visual handicap in children in the Czech Republic, as well as for detailed analysis of present practice of screening for ROP was recommended.

The association of indicators of fetal growth with visual acuity and hearing among conscripts

Impaired fetal growth is associated with increased susceptibility to several chronic diseases. We studied the association between birth weight, indicators of disproportional fetal growth, and impaired visual acuity and hearing in 4,300 conscripts from a well-defined region in Denmark from August 1, 1993, to July 31, 1994. From the standard health examination for conscripts, we obtained data on sight based on the Snellen's chart and data on hearing acuity based on audiometry. By means of record linkage, we obtained data on outcomes for the conscripts at birth from the Medical Birth Registry. From this registry, we have data on birth weight, gestational age, and birth length that were recorded from existing computerized registers based on the records of midwives. A birth weight of less than 3,000 gm and a body mass index at birth of less than 3.4 were associated with reduced visual acuity and impaired hearing. The results could be due to fetal brain programming or due to confounding, by early birth trauma or other factors.

Aetiology of childhood vision impairment, metropolitan Atlanta, 1991-93

Data from the population-based Metropolitan Atlanta Developmental Disabilities Surveillance Program (MADDSP) were used to describe the underlying causes of vision impairment (VI; corrected visual acuity in the better eye of 20/70 or worse) in young children (n = 228) in metropolitan Atlanta in 1991-93. Children with VI were identified through record review at multiple educational and medical sources. Children were categorised as having isolated VI or multiple disabilities (i.e. VI plus one or more of four additional developmental disabilities) and as having low vision (visual acuity 20/70-20/400) or blindness (visual acuity worse than 20/400). Medical conditions abstracted from MADDSP sources were reviewed to determine the probable aetiology of a child's VI. Aetiologies were assigned to one of three developmental time periods: prenatal, perinatal, or postnatal. Prenatal aetiologies were identified in 43% of the children; 38% of the prenatal aetiologies were genetic. Perinatal aetiologies were found in 27% of the children. Postnatal aetiologies were rare. Prenatal aetiologies were more common in children with isolated VI; perinatal and postnatal aetiologies were more common in children with multiple disabilities. Children with prenatal aetiologies tended to have less severe vision loss than did children with perinatal or postnatal aetiologies. The distribution varied by birthweight, but did not differ significantly by sex or race.

The contribution of low birth weight to severe vision loss in a geographically defined population

AIMS

To describe the birthweight specific rate of severe vision loss among babies born between 1 January 1984 and 31 December 1987 to mothers resident in a geographically defined area, to classify the causes of vision loss by time of origin, and to describe the associated sensory and motor impairments and disabilities.

METHODS

Cases were identified from a population register of children with early childhood impairment, which uses multiple sources of ascertainment. Further clinical information was retrieved from hospital records and by asking ophthalmologists caring for the children.

RESULTS

166 (1.25/1000 live births) children with severe vision loss diagnosed by the age of 5 years were identified. The rate among babies born weighing less than 1500 g at birth was 26 times higher than the rate for babies between 2500 g and 3499 g. These very low birthweight babies contribute 17.5% of all severely visually impaired children. Almost two thirds of children with severe vision loss have a lesion of prenatal origin. Other sensory or motor deficits are present in 69% of the children. Retinopathy of prematurity accounted for 5.4% of all visually impaired children and seven of the 166 children met the criteria for perinatal asphyxia.

CONCLUSIONS

Although the contribution made by babies with a low birth weight to overall severe vision loss in the community is small, many of these children have additional impairments and probably place considerable demands on health and educational services and families. Reduction in the frequency of vision problems in the preschool population as a whole is unlikely to occur until there are major advances in the understanding of the aetiology and prevention of eye conditions of genetic, prenatal, and developmental origin.

Visual impairment in Swedish children. III. Diagnoses

PURPOSE

To gain an overview of the spectrum of diagnoses among Swedish visually impaired children.

METHODS

An epidemiological study of all known visually impaired children was made by review of medical records.

RESULTS AND CONCLUSION

In all we found 2373 children, 0-19 years of age, with an age-specific prevalence of 10.9/10,000. The two largest diagnostic groups included neuro-ophthalmological and retinal diseases. The most frequent disorders were cerebral visual impairment, non-hereditary optic atrophy, retinal dystrophy (when regarded as a general entity), congenital hypoplasia of the optic nerve and congenital cataract. Nystagmus secondary to brain disorder, albinism, congenital nystagmus, retinopathy of prematurity and high myopia were also found in a considerable number of patients. The leading diagnoses in children with WHO-defined childhood blindness were non-hereditary optic atrophy, cerebral visual impairment and retinopathy of prematurity. A large proportion of the children, especially in the groups with neuro-ophthalmological disorders and malformations of the posterior segment had additional impairments, emphasizing the importance of a multi-disciplinary approach when assessing multi-handicapped children.

Visual impairment in Swedish children. II. Etiological factors

The analysis of etiological factors in a group of visually impaired children is of considerable importance when trying to find guidelines for possible preventive work. In this study we present etiological data on 2373 Swedish children. Data have been obtained by reviewing medical records on all known children with visual impairment throughout the country. In accordance with similar studies from industrialised countries, the group with prenatal etiology was the predominant, comprising 64% of the material. Within this group, half the patients had a disease of genetic origin. A total of 50% of all patients with prenatal etiology had an additional impairment, but in the group with diseases of genetic origin this proportion was smaller, only 40%. On the other hand, many children with additional impairments were found among those with an unspecified prenatal influence. Peri-/neonatal etiologies were found in 20% of the patients. In this group as many as 83% had additional impairments. This was even more pronounced among children delivered at term. The group with infantile/juvenile etiologies was small, 7%, with additional impairments in 66%. In 9% of all patients the etiology was classified as unknown. Among these, 80% had additional impairments. The visual impairment tended to be more pronounced, the later the disease was acquired. A male preponderance was seen in most etiological subgroups and in the material as a whole.

Visual impairment in Swedish children. I. Register and prevalence data

Knowledge of the epidemiology of visual impairment in children forms one of the cornerstones of pediatric ophthalmology. In contrast to e.g. the other Nordic countries, Sweden has had no efficient and continuous registration of visually impaired children. An epidemiological study on this subject has now been done, collecting data on all children and adolescents registered at the Low Vision Clinics throughout Sweden. In this work data on 2373 visually impaired children, 0-19 years of age and living throughout Sweden are presented. Data collected in the study include sex, date of birth, county, ocular diagnosis, systemic diagnosis, classification of visual impairment, aetiology and possible additional impairments. The prevalence of visual impairment as defined by WHO was 10.9/10,000 inhabitants in the current age group. A slight male preponderance was seen compared to the total population 0-19 years. This was not reduced when only non-genetic aetiological factors were taken into consideration. A total of 45% of the children had only a moderate visual impairment (WHO category 1), whereas approximately 25% were found in WHO categories 3,4 and 5, i.e. fulfilled the requirements for blindness. Additional impairments were found in 60% of the children. Mental impairment in combination with motor impairment or mental impairment exclusively were the most common ones seen.

Multihandicapped blind and partially sighted children in south Germany. II: Aetiology and pathogenesis

The results of a classification of the aetiology of visual impairment and mental retardation in a series of 239 multihandicapped blind and partially sighted children are reported. These children had been born between 1981 and 1987 and were examined in a population-based study in South Germany. There was marked aetiological heterogeneity. Most prominent were causes related to the perinatal period and late gestation which were found in 41% of the children. Among these, lesions of the visual pathways in preterm children were especially frequent and could be explained by periventricular leukomalacia in a large proportion. The distribution of the major aetiologic groups is different from populations with isolated mental retardation and populations with isolated visual impairment but similar to a Swedish population with spastic quadriplegia. The implications for the prevention of severe multiple impairments in children are discussed.

Causes of childhood blindness in Sri Lanka: results from children attending six schools for the blind

AIM

The survey aimed to identify the major treatable or preventable causes of visual loss in children attending blind schools in Sri Lanka so that appropriate control measures can be implemented.

METHOD

A total of 226 children with blindness (BL) or severe visual impairment (SVI) attending six schools for the blind were examined and details recorded using the WHO standard reporting form.

RESULTS

Cataract was responsible for 17% of BL/SVI and was the commonest 'avoidable' cause of childhood blindness. Bilateral microphthalmos accounted for one quarter of BL/SVI. Vitamin A deficiency was not a significant cause of visual morbidity.

CONCLUSION

The pattern of childhood blindness seen in this study is typical of a growing number of south east Asian countries which are developing rapidly. Childhood cataract is a major avoidable cause that can benefit from future intervention strategies.

Hereditary disease as a cause of childhood blindness: regional variation. Results of blind school studies undertaken in countries of Latin America, Asia and Africa

There is evidence from developed countries that genetic disease is the major cause of childhood blindness. Little data are available from most developing and newly industrialised countries concerning the relative importance of hereditary diseases as a cause of childhood blindness. Children in schools for the blind in 13 countries of Africa, Latin America and Asia were examined between 1990 and 1994 using a standardised method The anatomical site of abnormality and underlying aetiology were analysed for children with a corrected acuity in the better eye of less than 6/60 (severe visual impairment and blindness, svi/BL). In these countries II-39% of svi/BL was attributed to genetic disease. Genetic diseases were responsible for a higher proportion of childhood visual loss in countries with higher levels of socio-economic development. An autosomal recessive mode of inheritance was reported in 22-52% of children with genetic disease. Retinal dystrophies were the commonest form of genetic eye disease (49-80%) in all countries apart from Thailand and the Philippines where cataract was the commonest (43.9%). The role of consanguinity, and opportunities for further research are discussed.

Visual impairment in Nordic children. V. X-linked juvenile retinoschisis

In a study on 2,527 visually impaired children from four Nordic countries X-linked juvenile retinoschisis was diagnosed in 35 male children. Striking differences in frequency between the four countries were found, with 26 cases reported from Finland, 5 cases from Denmark, and 4 cases from Norway. None was reported from Iceland. The corresponding age and sex-specific prevalence rates of X-linked juvenile retinoschisis (N:1,000,000) were 44.5 in Finland, 8.8 in Denmark, and 7.9 in Norway. The uneven geographical distribution is possibly attributed to a 'founder effect' due to the settlements in Finland by European immigrants in the 17th century. The visual impairment of the registered cases was usually mild with 91.4% falling into WHO category 1. However, one child was totally blind, demonstrating large phenotypic heterogeneity. None of our cases had additional impairments. The majority were more than five years old, indicating a progressive course during childhood. Nevertheless, two children were diagnosed at the age of one. The most common age at registration was seven years, coinciding with the beginning of school attendance.

Nordic registers of visually impaired children

A Nordic study group, NORDSYN, consisting of ophthalmologists from Denmark (Thomas Rosenberg), Finland (Sirkka-Liisa Rudanko), Iceland (Gudmundur Viggosson), Norway (Tor Flage, Egill Hansen, Ruth Riise) and Sweden (Kristina Tornqvist), has compiled data from registers in Denmark, Finland, Iceland and Norway of 2527 visually impaired children. The Swedish register was established later in 1990. 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 among which congenital malformations and neuro-ophthalmological diseases were the most dominating. A coding system for aetiology was developed. It was demonstrated, that prenatal factors, including genetic aetiologies, were involved in a large proportion (66%) of the cases. The sex distribution revealed a dominance of males compared to the general population at the same age. The age-specific 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) were (N/100,000): Denmark 41, Finland 15, Iceland 19 and Norway 15. The differences were primarily presumed to be due to varying efficiency in registration. A coding system for additional impairments was developed. The proportion of visually impaired children with an additional mobility, hearing or mental impairment was 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.

Visual impairment in Nordic children. IV. Sex distribution

A Nordic study group of ophthalmologists, NORDSYN, has compiled registers in Denmark, Finland, Iceland and Norway of 2527 visually impaired children aged 0-17 years. This paper is concerned with the sex-distribution in the registers and has documented a statistically significant excess of males in two of the registers (Denmark and Finland). The dominance of males seems to be related to two main conditions: 1. Genetic factors. 2. Perinatal factors. The genetic factors are mainly concerned with X-linked inheritance. The fact that perinatal influences involve visual impairment in males more than in females is difficult to account for. It may be conjectured, that the basis for perinatal visual damage is determined by unknown prenatal, possibly genetic, factors.

Visual impairment in Nordic children. III. Diagnoses

The diagnoses, according to type and site and the degree of visual impairment, responsible for severe visual impairment in children below the age of 18, were analyzed in a material compiled from the national registers of visually impaired in Denmark, Finland, Iceland and Norway. Among 2527 children the predominant causes of visual impairment are ascribed to congenital malformations, neuro-ophthalmological diseases and retinal diseases. Optic atrophy is the leading single cause of severe visual impairment when all diagnoses are compared, and this also applies when all categories of visual impairment are included. Retinopathy of prematurity is the second principal cause of severe visual impairment, while cerebral amblyopia rates as the third most significant cause. Congenital cataract is also of considerable importance when all categories of visual impairment are compared. The differences registered between the Nordic countries were found to be within reasonable limits, except for a preponderance of neuro-ophthalmological diseases in the Danish material. This could be explained by a better medical supervision of mentally retarded patients in Denmark. Additional impairments occur in a large percentage of patients, but are unevenly distributed in the disease groups. A high frequency of additional impairments are found in the neuro-ophthalmological group and in the groups with congenital malformations, emphasizing the importance of a multidisciplinary evaluation when dealing with the visually impaired child.