International adoption has increased exponentially in the past two decades.1 In Spain, international adoptions are increasingly frequent.2

Internationally adopted children have specific characteristics that may lead to disease: prenatal exposure to alcohol, drugs, tobacco or other substances. They usually live in overcrowded quarters, with poor hygiene conditions, inadequate or insufficient nutrition and a limited number of caregivers. Many of them come from regions endemic for specific infectious diseases.3

Children at a severe disadvantage receive deficient health care, so they are susceptible to developing a greater number of diseases.4

Many of these factors may affect immature visual pathways and developing eyes.

Although there are some references to the visual and ocular status of internationally adopted children in the literature,1 only one study has been published specifically on this subject. There is a high prevalence of ophthalmological findings in children adopted from Eastern Europe.5 Little is known about ophthalmological pathology in these children. A recent study has correlated ophthalmological and neuropaediatric findings in children adopted from Eastern Europe.6

This paper presents the first systematic study on the ocular and visual status of children adopted from different regions.

From January 2010 to January 2012, the ophthalmology department of the Fundació Hospital de Nens of Barcelona studied 232 internationally adopted children. This prospective study was approved by the research council of the Fundació Hospital de Nens de Barcelona (University of Barcelona).

All patients were assessed by the same multidisciplinary team consisting of a paediatric ophthalmologist, a paediatric optometrist and a paediatrician specialised in international adoption.

We found ocular and vision disorders in 57.8% of the children under study. Few studies have assessed ophthalmological disorders in internationally adopted children. Grönlund et al.5 described a high frequency of ophthalmological findings (78%) in a population of children adopted from Eastern Europe. An association between these ophthalmological findings and neuropaediatric pathology has been established recently.6

When it comes to non-ophthalmological disorders, different studies show a greater prevalence of systemic pathology in internationally adopted children compared to non-adopted children and different prevalences depending on ethnic group and geographical region of origin.8,9 Children adopted from Ethiopia, who live with relatives for longer periods of time before being institutionalised, have fewer developmental delays and better growth.10 There is agreement that the longer the period of institutionalisation, the greater the incidence of pathology in adopted children.

In our study, the preadoption institutionalisation period was significantly longer in children from Groups 1 and 3. Institutionalisation lasting more than 24 months correlated with age, sex, and geographical region of origin. The preadoption institutionalisation period was longer in older children, in boys, and in children from Eastern Europe. In Group 1, the preadoption institutionalisation period was longer than 24 months in 57.4% of the children.

In our study, the prevalence of ametropia was 40.5%, while it is 7.7% in populations of non-adopted children.11

Although small differences between ethnic groups have been described in the prevalence of refraction errors in non-adopted children,12 our study found that ametropia was significantly more prevalent in children adopted from Central and South America.

Children from Central and South America had the highest prevalence of hyperopia. Myopia was most prevalent in children from Central and South America. Astigmatism was most prevalent in children from Central and South America and Eastern Europe. The presence of ametropia correlated significantly with the geographical region of origin and with the presence of nonrefractive ocular pathology.

Malnutrition in the early stages of life interferes with vision development. There is evidence that children affected by severe malnutrition in the first six months of life have a higher prevalence of ametropia (astigmatism and myopia), increased optic nerve cupping and RVT.13 In our series, we found RVT in four children from Group 1. Grönlund et al.6 found an 11% increase in the ITA and a 9% increase in the ITV in their sample of adopted children.

Vitamins and minerals, especially zinc, are essential to the development of the ocular globe and vision. Zinc is an essential cofactor in the metabolism of neurotransmitters, fatty acids, prostaglandins and melatonin.14 The most frequent ophthalmological manifestation of severe zinc deficiency is periocular vesiculopustular rash,15 which we did not find in any of our patients.

In populations that suffer from malnutrition, 45% of children develop iron deficiency anaemia.16 Iron is essential to the development of the central nervous system, cellular differentiation, protein and hormone synthesis and different pathways of cellular metabolism,17 even in the optic pathways. There is evidence that suggests that myelination may be partially dependent on iron.18 Given the importance of nutrition in the early months of life, prospective studies need to be conducted to assess the relationship between the nutritional status of these children and ophthalmological pathology.

Maternal smoking during pregnancy has a negative impact on the foetus and the child.19 The higher mean hyperopia values in children exposed to tobacco smoke during gestation and childhood suggests that environmental factors related to tobacco use may have long-term effects on refraction.20 A study published recently21 demonstrated that patients that smoke are at higher risk of recurrence of ocular inflammatory diseases.

In our study, children adopted from Eastern Europe (Group 1) had the highest prevalence of strabismus and optic nerve hypoplasia, although the difference did not reach statistical significance. The total percentage of children that had strabismus in our series was 13.8%. The prevalence of strabismus in another series of adopted children was 32%,5 while the prevalence in non-adopted children ranges from 3% to 8%.22

In our study, esotropia was more prevalent than exotropia (esotropia to exotropia ratio, 1.21). Other authors have reported ratios greater than 2 in studies of adopted5 and non-adopted11 children.

We found four cases of ONH among the children adopted from Russia. A history of maternal alcohol consumption during pregnancy was only verified in one, probably because this fact is usually not known or not reported by adoptive parents. Grönlund et al.5 reported a similar prevalence of ONH (4/72; 5.5%) in a group of children adopted from Eastern Europe.

We did not find optic neuritis caused by lead in children from China, even though 14% of these children had high serum levels of this metal.23

The high prevalence of strabismus and ONH in children adopted from Eastern Europe may be related to alcohol and substance use. Russia has a high rate of alcohol consumption per capita, and the use of illegal drugs has been increasing. Alcohol affects synaptogenesis in the foetal brain,24 inducing neuronal degeneration.

The prevalence of prenatal exposure to illegal drugs in internationally adopted children is unknown. Many countries do not document this information to avoid unflattering publicity.25

In our study, amblyopia was diagnosed in 18 children (7.8%). In the general paediatric population, 2% of the children develop amblyopia, while Grönlund et al.5 found a prevalence of 15% in their series of children adopted from Russia. We found the highest frequency of amblyopia in children from Group 2 (11/95; 11.6%), although this finding was not statistically significant.

The higher prevalence of amblyopia in children from Group 2 may be due to malnutrition and visual understimulation. Most of the problems found in adopted children upon arrival to Spain have been attributed to deficient institutional care in early stages of development.26 A few institutionalised children had never been outdoors and had not been exposed to the visual stimulation required for the normal development of the optic pathway. Some caregivers in orphanages wear masks, depriving the children of the experience of seeing human faces.27 The visual stimuli of shapes, colours, contrasts and movement are essential to the correct development of VA and binocular vision. A lack of visual stimulation is associated with the pathogenesis of amblyopia.

This study emphasises the need for an initial ophthalmological assessment and the ophthalmological followup of all internationally adopted children. Paediatricians and adoptive parents must be watchful given the risk of visual abnormalities in these children, and provide the necessary resources for early diagnosis and treatment.

The authors have no conflicts of interest to declare.